Consumer medicine information

Axit

Mirtazapine

BRAND INFORMATION

Brand name

Axit

Active ingredient

Mirtazapine

Schedule

S4

 

Consumer medicine information (CMI) leaflet

Please read this leaflet carefully before you start using Axit.

What is in this leaflet

This leaflet answers some common questions about Axit. It does not contain all the available information. It does not take the place of talking to your doctor or pharmacist.

All medicines have risks and benefits. Your doctor has weighed the risks of you taking Axit against the benefits they expect it will have for you.

If you have any concerns about taking this medicine, ask your doctor or pharmacist.

Keep this leaflet with your medicine. You may need to read it again.

What Axit is used for

Axit is used in the treatment of depression including relapse prevention.

Depression is longer lasting or more severe than "low moods" everyone has from time to time due to the stress of everyday life. It is thought to be caused by a chemical imbalance in parts of the brain. This affects your whole body and can cause emotional and physical symptoms such as feeling low in spirit, loss of interest in activities, unable to enjoy life, poor appetite or overeating, disturbed sleep, often waking up early, loss of sex drive, lack of energy and feeling guilty over nothing.

This medicine corrects this chemical imbalance and may help relieve the symptoms of depression.

Your doctor, however, may prescribe it for another purpose.

Ask your doctor if you have any questions about why it has been prescribed for you.

This medicine is only available with a doctor's prescription.

Axit is not addictive.

Before you take Axit

When you must not take it

Do not take Axit:

  • if you are allergic to medicines containing mirtazapine
  • if you are allergic to any of the ingredients listed at the end of this leaflet.

Some of the symptoms of an allergic reaction may include skin rash, itching or hives, swelling of the face, lips, mouth, throat or other parts of the body, shortness of breath, wheezing or trouble breathing.

Do not take Axit if you are taking another medicine for depression called a monoamine oxidase inhibitor (MAOI) or have been taking an MAOI within the last 14 days. If you stop taking Axit, do not take MAOI during the next two weeks either. Taking Axit with an MAOI may cause a serious reaction with a sudden increase in body temperature, extremely high blood pressure and severe convulsions.

Examples of this type of medicine include phenelzine, tranylcypromine and selegiline.

Ask your doctor or pharmacist if you are not sure if you are or if you have been taking a MAOI medicine.

Do not take Axit if the packaging is torn or shows signs of tampering.

Do not take Axit if the expiry date printed on the pack has passed.

If you are not sure whether you should start taking Axit, talk to your doctor

Do not take Axit if you have galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption, as this medicine contains lactose.

Before you start to take it

Do not give Axit to a child or adolescent. The safety of Axit in patients under 18 years has not been established.

Tell your doctor if:

  1. you are allergic to any other medicines, foods, dyes or preservatives.
  2. you are pregnant or plan to become pregnant
Like most medicines of this kind, Axit is not recommended to be used during pregnancy. Your doctor will discuss the risks and benefits of taking Axit when pregnant.
  1. you are breastfeeding or wish to breastfeed.
It is not known whether Axit passes into breastmilk.
  1. if you have or have had any medical conditions, especially the following:
  • thoughts of suicide or self-harm
  • epilepsy (fits or convulsions)
  • liver disease such as jaundice
  • kidney disease
  • heart disease
  • low blood pressure
  • certain kinds of heart conditions that may change your heart rhythm, a recent heart attack, heart failure, or take certain medicines that may affect the heart's rhythm.
  • any mental illness (e.g. schizophrenia and manic depression)
  • diabetes
  • glaucoma (increased pressure in the eye)
  • problems in urinating due to an enlarged prostate
  • unexplainable high fever, sore throat and mouth ulcers
  • galactose intolerance
  • glucose-galactose malabsorption.

If you have not told your doctor about any of the above, tell them before you take Axit.

Tell your doctor if you react badly to lactose or milk before you start taking Axit. Axit tablets contain lactose.

Taking other medicines

Tell your doctor if you are taking any other medicines, including medicines you buy without a prescription from a pharmacy, supermarket or health food shop.

Some medicines may be affected by Axit or may affect how well it works. These include:

  • other medicines (eg. SSRIs, venlafaxine, L-tryptophan, nefazodone) for depression, anxiety, obsessive compulsive disorders or pre-menstrual dysphoric disorder
  • Monoamine Oxidase Inhibitors (such as tranylcypromine, phenelzine, and selegiline)
  • medicines containing St. John's Wort (hypericum perforatum)
  • phenytoin or carbamazepine, medicines used to treat epilepsy
  • benzodiazepines, medicines used to treat anxiety and sleeping problems
  • lithium, a medicine used to treat some psychiatric conditions
  • methylene blue (used to treat high levels of methemoglobin in the blood)
  • tramadol, a pain killer
  • morphine, a medicine for severe pain
  • cetirizine, a medicine for allergies
  • warfarin, a medicine used to prevent blood clotting
  • linezolid, erythromycin, an antibiotic
  • rifampicin, a medicine used to treat tuberculosis
  • medicines used to treat fungal infections such as ketoconazole
  • HIV/AIDS medications
  • cimetidine, a medicine used to treat reflux and stomach ulcers
  • triptans such as sumatriptan, naratriptan and zolmitriptan, medicines used to treat migraine
  • medicines that may affect the heart's rhythm such as certain antibiotics and some anti-psychotics.

Your doctor can tell you what to do if you are taking any of these medicines.

Your doctor and pharmacist may have more information on medicines to be careful with or avoid while taking Axit

If you are not sure whether you are taking any of these medicines, check with your doctor or pharmacist.

How to take Axit

Follow all directions given to you by your doctor and pharmacist carefully. They may differ from the information contained in this leaflet.

How much to take

Your doctor will tell you how much Axit to take each day. Take exactly the amount your doctor tells you.

The usual starting dose is 15 mg per day. Your doctor may slowly increase this dose depending on how you respond to this medicine. The effective dose for most people is usually between 30 and 45 mg daily.

Your doctor may have prescribed a different dose.

If you do not understand the instructions on the box, ask your doctor or pharmacist for help.

When to take it

Take your medicine at about the same time each day.

Your doctor will tell you when to take your tablets.

The tablet(s) should be taken at the same time each day, preferably as a single night-time dose before going to bed; if recommended by your doctor, Axit may be taken in sub-doses equally divided over the day (once in the morning and once at night-time before going to bed).

How to take it

Swallow the tablet(s), without chewing, together with some water or other fluid.

Do not crush or chew the tablets.

Axit 15 and Axit 30 tablets can be divided in half along the breakline, if advised by your doctor or pharmacist.

Axit can be taken with or without food.

How long to take it

Keep taking Axit until your doctor tells you to stop.

For depression, the length of treatment will depend on how quickly your symptoms improve. Most antidepressants take time to work, so do not be discouraged if you don't feel better right away. Some of your symptoms may improve in 1 to 2 weeks but it can take up to 2 - 4 weeks longer to feel the full benefit of the medicine.

Even when you feel well, you will usually have to take Axit for 4 to 6 months or even longer to make sure the benefits will last.

If you forget to take it

ONCE DAILY DOSING

If you forget to take the tablet before you go to bed, do not take the missed dose the next morning. It may cause drowsiness or sleepiness during the day. Continue treatment in the evening with your normal dose.

TWICE DAILY DOSING

  • Morning dose forgotten - simply take it together with your evening dose.
  • Evening dose forgotten - do not take it with the next morning dose. Continue treatment with your normal morning and evening doses.
  • Both doses forgotten - do not try to make up for the missed tablets. Continue with your usual morning and evening dose the next day.

If you have trouble remembering to take your medicine, ask your pharmacist for some hints.

If you take too much (overdose)

Immediately telephone your doctor or the Poisons Information Centre (telephone 13 11 26) for advice, or go to Accident and Emergency at the nearest hospital, if you think you or anyone else may have taken too much Axit. Do this even if there are no signs of discomfort or poisoning. You may need urgent medical attention.

If you take too many Axit tablets, you may feel drowsy, dizzy, confused and agitated.

You may also have changes to your heart rhythm (fast, irregular heartbeat) and/or fainting which could be symptoms of a life-threatening condition known as Torsades de Pointes.

While you are taking Axit

Things you must do

Tell your doctor immediately if you develop fever, chills, sore throat or mouth ulcers or other signs of frequent infections. Stop taking Axit and consult with your doctor for a blood test. In rare cases Axit can cause disturbances in the production of blood cells (bone marrow depression). Some people become less resistant to infection because Axit can cause a temporary shortage of white blood cells (granulocytopenia). In rare cases Axit can also cause a shortage of red and white blood cells, as well as blood platelets (aplastic anaemia), a shortage of blood platelets (thrombocytopenia) or an increase in the number of white blood cells (eosinophilia). While rare, these symptoms most commonly appear after 4 - 6 weeks of treatment.

Tell your doctor immediately or go to the nearest hospital for treatment if you have any suicidal thoughts or other mental/mood changes. Occasionally, the symptoms of depression or other psychiatric conditions may include thoughts of harming yourself or committing suicide. Until the full antidepressant effect of your medicine becomes apparent, it is possible these symptoms may increase in the first few weeks of treatment.

Information from clinical trials have shown an increased risk of suicidal behaviour in young adults aged less than 25 years with psychiatric conditions who were treated with an antidepressant.

If you or someone you know is showing warning signs of suicide-related behaviour while taking Axit, contact your doctor or a mental health professional right away or go to the nearest hospital for treatment. These signs include:

  • thoughts or talk about death or suicide
  • thoughts or talk of self-harm or harm to others
  • any recent attempts of self harm
  • increase in aggressive behaviour, irritability or agitation.

All mentions of suicide or violence must be taken seriously.

You may find it helpful to tell a relative or close friend that you are depressed and ask them to read this leaflet. You might ask them to tell you if they think your depression is getting worse, or if they are worried about changes in your behaviour.

Tell your doctor if you become pregnant while taking this medicine. Do not stop taking your tablets until you have spoken to your doctor.

If you use Axit until, or shortly before birth, your baby should be supervised for possible adverse effects.

Ask your doctor whether you can breastfeed, while taking Axit.

Tell your doctor if, for any reason, you have not taken your medicine exactly as prescribed. Otherwise, your doctor may think that it was not effective and change your treatment unnecessarily.

Tell your doctor if you feel the tablets are not helping your condition.

Be sure to keep all of your appointments with your doctor so that your progress can be checked. You may need to have blood tests from time to time.

Before starting any new medicine, tell your doctor or pharmacist that you are taking Axit.

Tell all the doctors, dentists and pharmacists who are treating you that you are taking Axit.

Things you must not do

Do not drive or operate machinery until you know how Axit affects you. Axit may cause drowsiness, dizziness or sleepiness in some people and affect alertness and concentration. If any of these occur, do not drive, operate machinery or do anything else that could be dangerous.

Do not suddenly stop taking Axit, or lower the dose, without first checking with your doctor.

Do not let yourself run out of medicine over weekends or on holidays.

Do not stop taking Axit, even if you feel better, unless advised by your doctor. Suddenly stopping Axit may cause nausea (feeling sick), headache, dizziness, anxiety, agitation.

Your doctor may want you to gradually reduce the amount of Axit you are taking before stopping completely.

Do not use Axit to treat any other conditions unless your doctor tells you to.

Do not give Axit to anyone else, even if their symptoms seem similar to yours or if they have the same condition as you.

Things to be careful of

You are advised not to drink any alcohol while taking Axit. Combining Axit and alcohol can make you more sleepy and less alert. Your doctor may suggest you avoid alcohol while being treated with this medicine.

Side effects

Tell your doctor or pharmacist as soon as possible if you do not feel well while you are taking Axit.

Axit helps most people with depression, but it may have unwanted side effects in a few people. All medicines can have side effects. Sometimes they are serious, most of the time they are not. You may need medical treatment if you get some of the side effects.

Ask your doctor or pharmacist to answer any questions you may have.

Do not be alarmed by this list of possible side effects. You may not experience any of them.

Tell your doctor if you notice any of the following and they worry you:

  • lethargy, drowsiness or sleepiness
  • headache
  • tiredness
  • increase in appetite and weight gain
  • dry mouth
  • nausea, vomiting
  • diarrhoea
  • constipation
  • dizziness
  • dizziness or faintness when getting up quickly from a lying or sitting position (low blood pressure)
  • abnormal sensations in the mouth, sensations of numbness in the mouth or swelling in the mouth
  • aggression
  • swollen ankles or feet as a result of fluid accumulation (oedema)
  • rash or skin eruptions
  • nightmares/vivid dreams
  • tingling fingers or toes
  • painful joints
  • back pain
  • muscle aches and pains
  • restless legs
  • abnormal sensation in the skin for example burning, stinging, tickling or tingling
  • urge to move
  • speech disorders
  • difficulty in passing urine (urinary retention)
  • anxiety, insomnia. These may be symptoms of depression
  • increased prolactin hormone levels in blood (hyperprolactinaemia, including symptoms such as enlarged breasts and/or milky nipple discharge)
  • sleepwalking
  • prolonged painful erection of the penis

Tell your doctor immediately or go to Accident and Emergency at the nearest hospital if you notice any of the following:

  • suicidal ideation or behaviour
  • epileptic attack (seizures)
  • shaking or tremors
  • sudden muscle contractions (myoclonus)
  • attack of excessive excitability (mania)
  • agitation
  • confusion
  • hallucinations
  • changes to your heart rhythm
  • fainting
  • yellow colouring of eyes or skin; this may suggest disturbance in liver function
  • abdominal pain and nausea; this may suggest inflammation of the pancreas
  • generalised fluid retention with weight gain
  • skin rash, itching or hives; swelling of the face, lips or tongue which may cause difficulty breathing
  • severe skin reactions
  • signs of infection such as sudden unexplainable high fever, sore throat and mouth ulcers
  • a combination of symptoms such as fever, sweating, increased heart rate, diarrhoea, (uncontrollable) muscle contractions, shivering, overactive reflexes, restlessness, mood changes, unconsciousness and increased salivation (serotonin syndrome)
  • muscle pain, stiffness and/or weakness, darkening or discolouration of the urine (rhabdomyolysis)

Other side effects not listed above may also occur in some patients.

Tell your doctor if you notice anything else that is making you feel unwell.

Ask your doctor or pharmacist if you don't understand anything in this list.

After taking Axit

Storage

Keep your tablets in their blister pack until it is time to take them The tablets may not keep as well if you take them out of the blister pack.

Store below 30°C in a dark, dry place.

Do not store Axit or any other medicine in the bathroom or near a sink. Heat and dampness will destroy some medicines.

Keep this medicine where young children cannot reach it. A locked cupboard at least one-and-a-half metres above the ground is a good place to store medicines.

Disposal

Return any unused medicine to your pharmacist.

Medicines should not be disposed of via waste water or household waste.

Product description

What it looks like

Axit 15 tablets are round, yellow, film-coated tablets marked "MR|15" on one side and "G" on the other.

Axit 30 tablets are round, buff coloured, film-coated tablets marked "MR|30" on one side and "G" on the other.

Axit 45 tablets are round, white, film-coated tablets marked with "MR 45" on one side and "G" on the other.

The tablets for the 15 mg and 30 mg strengths have a breakline and can be broken into two halves if required.

Axit 15, Axit 30 and Axit 45 are available in blister packs of 30 tablets.

Ingredients

The active ingredient in Axit is mirtazapine. Each Axit tablet contains either 15 mg, 30 mg or 45 mg of mirtazapine.

The tablets also contain the following inactive ingredients:

  • lactose monohydrate
  • maize starch
  • colloidal anhydrous silica
  • hyprolose
  • magnesium stearate
  • Opadry Buff OY-LS-37200 (contains iron oxide yellow CI77492 [E172], iron oxide red CI77491 [E172], iron oxide black CI77499 [E172], in 30 mg tablets only)
  • Opadry II complete film coating system 39F52901 Yellow (contains quinoline yellow CI47005 and iron oxide yellow CI77492, in 15 mg tablets only)
  • Opadry White OY-LS-28908 (in 45 mg tablets only).

Axit tablets contain trace amounts of sulfites.

The tablets are gluten free.

Manufacturer

Axit is made in Australia by:

Alphapharm Pty Ltd
Level 1, 30 The Bond
30 - 34 Hickson Road
Millers Point NSW 2000
www.mylan.com.au

Australian registration number:

Axit 15 - AUST R 97194 (blister pack)

Axit 30 - AUST R 97195 (blister pack)

Axit 45 - AUST R 164493 (blister pack)

This leaflet was prepared in February 2021.

Axit_cmi\Feb21/00

Published by MIMS March 2021

BRAND INFORMATION

Brand name

Axit

Active ingredient

Mirtazapine

Schedule

S4

 

1 Name of Medicine

Mirtazapine.

2 Qualitative and Quantitative Composition

Each Axit tablet contains either 15 mg, 30 mg or 45 mg of mirtazapine.

Excipients with known effect.

Lactose, and traces of sulfites and galactose.
For the full list of excipients, see Section 6.1 List of Excipients.

3 Pharmaceutical Form

Axit 15.

Circular, normal convex, yellow, film-coated tablets debossed "MR/15" on one side and "G" on the other. The tablets have a breakline and can be broken into two halves if required.

Axit 30.

Circular, normal convex, buff, film-coated tablets debossed "MR/30" on one side and "G" on the other. The tablets have a breakline and can be broken into two halves if required.

Axit 45.

Circular, normal convex, white, film-coated tablets debossed "MR 45" on one side and "G" on the other.

4 Clinical Particulars

4.1 Therapeutic Indications

Treatment of major depression including relapse prevention.

4.2 Dose and Method of Administration

The tablets should be taken orally with water and swallowed without chewing.

Adults.

Treatment should begin with 15 mg daily. The dosage generally needs to be increased to obtain an optimal clinical response. The effective daily dose is usually between 30 and 45 mg, but responses have been observed at 60 mg per day.

Elderly.

The recommended dose is the same as that for adults. In elderly patients an increase in dosing should be done under close supervision to elicit a satisfactory and safe response.
The clearance of mirtazapine may be decreased in patients with renal or hepatic insufficiency. This should be taken into account when prescribing Axit to this category of patients (see Section 4.4 Special Warnings and Precautions for Use; Section 5.2 Pharmacokinetic Properties).
Mirtazapine has a half-life of 20 to 40 hours and, therefore, mirtazapine is suitable for once a day administration. It should be taken preferably as a single night time dose before going to bed. Mirtazapine may also be given in subdoses equally divided over the day (once in the morning and once at night time).
Treatment should preferably be continued until the patient has been completely symptom free for 4 to 6 months. After this, treatment can be gradually discontinued to avoid withdrawal symptoms (see Section 4.4 Special Warnings and Precautions for Use). Mirtazapine begins to exert its effect in general after 1-2 weeks of treatment. Treatment with an adequate dose should result in a positive response within 2 to 4 weeks. With an insufficient response, the dose can be increased up to the maximum dose. If there is no response within a further 2 to 4 weeks, then treatment should be stopped.

Children and adolescents (< 18 years of age).

In placebo controlled trials, safety and efficacy of mirtazapine in the treatment of children and adolescents under the age of 18 years with major depressive disorder have not been established. Safety and efficacy in this population cannot be extrapolated from adult data. Therefore, Axit should not be used in children and adolescents under the age of 18 years.

4.3 Contraindications

Hypersensitivity to mirtazapine or to any of the excipients.
Monoamine oxidase (MAO) inhibitors as concomitant therapy. It is recommended that mirtazapine not be used in combination with MAO inhibitors, or within 14 days of initiating or discontinuing therapy with a MAO inhibitor (see Section 4.5 Interactions with Other Medicines and Other Forms of Interactions).

4.4 Special Warnings and Precautions for Use

Clinical worsening and suicide risk.

The risk of suicidality (suicidal ideation and suicidal behaviours) is inherent in depression and may persist until significant remission occurs. This risk must be considered in all depressed patients. Patients with depression may experience worsening of their depressive symptoms and/or the emergence of suicidal ideation and/or behaviours whether or not they are taking antidepressant medication, and this risk may persist until significant remission occurs. Suicide is a known risk in depression, and certain other psychiatric disorders, and these disorders themselves are the strongest predictors of suicide. As improvement may not occur during the first few weeks or more of treatment, patients should be closely monitored for clinical worsening and suicidality, especially at the beginning of a course of treatment or at the time of dose changes, either increases or decreases. Consideration should be given to changing the therapeutic regimen, including possibly discontinuing the medication, in patients whose depression is persistently worse or whose emergent suicidality is severe, abrupt in onset or was not part of the patient's presenting symptoms. Patients (and caregivers of patients) should be alerted about the need to monitor for any worsening of their condition and/or the emergence of suicidal ideation or behaviour or thoughts of harming themselves and to seek medical advice immediately if these symptoms present. Patients with comorbid depression associated with other psychiatric disorders being treated with antidepressants should be similarly observed for clinical worsening and suicidality.
Pooled analysis of short-term placebo controlled trials of antidepressant drugs (SSRIs and others) showed that these drugs increased the risk of suicidal ideation and/or behaviours in children, adolescents and young adults (aged 18-24 years) with major depressive disorder (MDD) and other psychiatric disorders during the initial treatment (generally the first one to two months). Short-term studies did not show an increase in the risk of suicidality with antidepressants compared to placebo in adults beyond the age of 24 years; there was a reduction with antidepressants compared to placebo in adults aged 65 years and older.
The pooled analyses of placebo controlled trials in children and adolescents with MDD, obsessive compulsive disorder (OCD) or other psychiatric disorders included a total of 24 short-term trials (4 to 16 weeks) of 9 antidepressant drugs in over 4,400 patients. The pooled analyses of placebo controlled trials in adults with MDD or other psychiatric disorders included a total of 295 short-term trials (median duration of 2 months) of 11 antidepressant drugs in over 77,000 patients. There was considerable variation in the risk of suicidality among drugs, but a tendency towards an increase in the younger patients for almost all drugs studied. There were differences in absolute risk of suicidality across different indications, with the highest incidence in MDD trials. The risk differences (drug vs placebo), however, were relatively stable within age strata and across indications.
No suicides occurred in any of the paediatric trials. There were few suicides in the adult trials, but the number was not sufficient to reach any conclusion about the effect of antidepressants on suicide. It is unknown whether suicidality risk extends to longer-term use, i.e. beyond several months. However, there is substantial evidence from placebo controlled maintenance trials in adults with depression that the use of antidepressants can delay the recurrence of depression.
Symptoms of anxiety, agitation, panic attacks, insomnia, irritability, hostility (aggressiveness), impulsivity, akathisia (psychomotor restlessness), hypomania and mania have been reported in adults, adolescents and children being treated with antidepressants for major depressive disorder as well as for other indications, both psychiatric and nonpsychiatric. Although a causal link between the emergence of such symptoms and either worsening of depression and/or emergence of suicidal impulses has not been established, there is concern that such symptoms may be precursors of emerging suicidality.
Families and caregivers of children and adolescents being treated with antidepressants for major depressive disorder or for any other condition (psychiatric or nonpsychiatric) should be informed about the need to monitor these patients for the emergence of agitation, irritability, unusual changes in behaviour and other symptoms described above, as well as the emergence of suicidality and to report such symptoms immediately to health care providers. It is particularly important that monitoring be undertaken during the initial few months of antidepressant treatment or at times of dose increase or decrease.
Prescriptions for Axit should be written for the smallest quantity of tablets consistent with good patient management, in order to reduce the risk of overdose.

Conditions which need supervision.

Careful dosing as well as regular and close monitoring is necessary in patients with:
Epilepsy and organic brain syndrome. (See Section 4.8 Adverse Effects (Undesirable Effects)). Mirtazapine should be introduced cautiously in patients who have a history of seizures. Treatment should be discontinued in any patient who develops seizures, or where there is an increase in seizure frequency.
Hepatic impairment.
Renal insufficiency. Mirtazapine is substantially excreted by the kidney (75%) and the risk of decreased clearance of this drug is greater in patients with impaired renal function.
Cardiac diseases. Like conduction disturbances, angina pectoris and recent myocardial infarct, where normal precautions should be taken and concomitant medicines carefully administered.
Low blood pressure and conditions that would predispose patients to hypotension (dehydration, hypovolaemia and treatment with antihypertensive medication).
Diabetes mellitus. In patients with diabetes, antidepressants may alter glycaemic control. Insulin and/or oral hypoglycaemic dosage may need to be adjusted and close monitoring is recommended.
Like with other antidepressants, the following should also be taken into account.
Worsening of psychotic symptoms can occur when antidepressants are administered to patients with schizophrenia or other psychotic disturbances; paranoid thoughts can be intensified.
A major depressive episode may be the initial presentation of bipolar disorder. It is generally believed that treating such an episode with an antidepressant alone can increase the likelihood of precipitation of a mixed/manic episode in patients at risk of bipolar disorder. Prior to initiating treatment with an antidepressant, patients should be adequately screened to determine if they are at risk for bipolar disorder; such screening should include a detailed psychiatric history, including a family history of suicide, bipolar disorder and depression. When the depressive phase of the bipolar disorder is being treated, it can transform into the manic phase. Patients with a history of mania/hypomania should be closely monitored. Axit should be discontinued in any patient entering a manic phase.
Care should be taken in patients with micturition disturbances like prostate hypertrophy (although problems are not to be expected because mirtazapine possesses only very weak anticholinergic activity).
Acute narrow angle glaucoma and increased intraocular pressure (however, mirtazapine has weak anticholinergic activity).
Akathisia/psychomotor restlessness. The use of antidepressants has been associated with the development of akathisia, characterised by a subjectively unpleasant or distressing restlessness and need to move often accompanied by an inability to sit or stand still. This is most likely to occur within the first few weeks of treatment. In patients who develop these symptoms, increasing the dose may be detrimental.
The effect of mirtazapine on QTc interval was assessed in a randomised, placebo and moxifloxacin controlled clinical trial involving 54 healthy volunteers using exposure response analysis. This trial revealed that both 45 mg (therapeutic) and 75 mg (supratherapeutic) doses of mirtazapine did not affect the QTc interval to a clinically meaningful extent. During the post-marketing use of mirtazapine, cases of QT prolongation, torsades de pointes, ventricular tachycardia, and sudden death, have been reported.
The majority of reports occurred in association with overdose or in patients with other risk factors for QT prolongation, including concomitant use of QTc prolonging medicines (see Section 4.5 Interactions with Other Medicines and Other Forms of Interactions; Section 4.9 Overdose). Caution should be exercised when mirtazapine is prescribed in patients with known cardiovascular disease or family history of QT prolongation, and in concomitant use with other medicinal products thought to prolong the QTc interval.
Mirtazapine is not addictive. Post-marketing experience shows that abrupt termination of treatment after long-term administration may sometimes result in withdrawal symptoms. The majority of withdrawal reactions are mild and self limiting. Among the various reported withdrawal symptoms, dizziness, agitation, anxiety, headache and nausea are the most frequently reported. Even though they have been reported as withdrawal symptoms, it should be realised that these symptoms may be related to an underlying disease. As advised, see Section 4.2 Dose and Method of Administration, it is recommended to discontinue treatment with Axit gradually.

Jaundice.

Treatment should be discontinued if jaundice occurs.

Hyponatremia.

Hyponatremia has been reported very rarely with the use of mirtazapine. Caution should be exercised in patients at risk, such as elderly patients or patients concomitantly treated with medications known to cause hyponatremia.

Serotonin syndrome.

Development of serotonin syndrome may occur in association with treatment with SSRIs and SNRIs, particularly when given in combination with MAO inhibitors (see Section 4.3 Contraindications; Section 4.5 Interactions with Other Medicines and Other Forms of Interactions) or other serotonergic agents (see Section 4.5 Interactions with Other Medicines and Other Forms of Interactions). Symptoms and signs of serotonin syndrome include rapid onset of neuromuscular excitation (hyper-reflexia, incoordination, myoclonus, tremor), altered mental status (confusion, agitation, hypomania) and autonomic dysfunction (diaphoresis, diarrhoea, fever, shivering and rapidly fluctuating vital signs). Treatment with Axit should be discontinued if such events occur and supportive symptomatic treatment initiated. From post-marketing experience it appears that serotonin syndrome occurs very rarely in patients treated with mirtazapine alone (see Section 4.8 Adverse Effects (Undesirable Effects)).

Lactose.

Patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption should not take this medicine.

Severe cutaneous adverse reactions.

Severe cutaneous adverse reactions (SCARs) including Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), drug reaction with eosinophilia and systemic symptoms (DRESS), bullous dermatitis and erythema multiforme, which can be life-threatening or fatal, have been reported in association with mirtazapine treatment.
If signs and symptoms suggestive of these reactions appear, mirtazapine should be withdrawn immediately. If the patient has developed one of these reactions with the use of mirtazapine, treatment with mirtazapine must not be restarted in this patient at any time.

Neutropenia, agranulocytosis.

Bone marrow depression, usually presenting as granulocytopenia or agranulocytosis, has been reported during treatment with mirtazapine. The symptoms mostly appear after 2 to 6 weeks of treatment. The bone marrow depression is, in general, reversible after termination of treatment. However, in very rare cases agranulocytosis can be fatal. Reversible agranulocytosis has been reported as a rare occurrence in clinical studies with mirtazapine. In the post-marketing period with mirtazapine, very rare cases of agranulocytosis have been reported, mostly reversible, but in some cases fatal. All fatal cases concerned patients over 65 years. Post-marketing data indicate that the rate of occurrence of agranulocytosis and agranulocytosis-like disorders (whether or not causally related) amongst mirtazapine users is no greater than that in the background population. One should, therefore, be alert for symptoms like fever, sore throat, stomatitis or other signs of infections. If such symptoms occur the treatment should be stopped and blood counts taken.

Use in hepatic impairment.

See Section 4.2 Dose and Method of Administration; Section 5.2 Pharmacokinetic Properties, Pharmacokinetics in special populations, Renal and/or hepatic impairment.

Use in renal impairment.

See Section 4.2 Dose and Method of Administration; Section 5.2 Pharmacokinetic Properties, Pharmacokinetics in special populations, Renal and/or hepatic impairment.

Use in the elderly.

Elderly patients are often more sensitive, especially with regard to the undesirable effects of antidepressants. During clinical research with mirtazapine, undesirable effects have not been reported more often in elderly patients than in other age groups (see Section 4.2 Dose and Method of Administration; Section 5.1 Pharmacodynamic Properties, Clinical trials).

Paediatric use.

Mirtazapine should not be used to treat children and adolescents under the age of 18 years. Suicide related behaviours (suicide attempt and suicidal thoughts), and hostility (predominantly aggression, oppositional behaviour and anger) were more frequently observed in clinical trials among children and adolescents treated with antidepressants compared to those treated with placebo. If, based on clinical need, a decision to treat is nevertheless taken; the patient should be carefully monitored for the appearance of suicidal symptoms. In addition, long-term safety data in children and adolescents concerning growth, maturation and cognitive and behavioural development are lacking.

Effects on laboratory tests.

For adverse effects related to laboratory tests, see Section 4.8 Adverse Effects (Undesirable Effects).

4.5 Interactions with Other Medicines and Other Forms of Interactions

Pharmacokinetic interactions.

Mirtazapine is extensively metabolised by CYP2D6 (resulting in the 8-hydroxy metabolite) and CYP3A4 (N-demethyl and N-oxide metabolites) and to a lesser extent by CYP1A2. An interaction study with healthy volunteers showed no influence of paroxetine, a CYP2D6 inhibitor, on mirtazapine pharmacokinetics in steady state.
Coadministration of the potent inhibitor of CYP3A4, ketoconazole, in healthy male volunteers, increased mirtazapine peak plasma concentration levels and AUC by approximately 40% and 50%, respectively.
When cimetidine (weak inhibitor of CYP1A2, CYP2D6 and CYP3A4) is administered with mirtazapine, the mean plasma concentration of mirtazapine may increase more than 50%. The mirtazapine dose may have to be decreased when concomitant treatment with cimetidine is started or increased when cimetidine treatment is ended. Caution should be exercised and the dose may have to be decreased when coadministering mirtazapine with potent CYP3A4 inhibitors, HIV protease inhibitors, azole antifungals, ketoconazole, erythromycin, cimetidine or nefazodone. Carbamazepine and phenytoin, inducers of CYP3A4, increased mirtazapine clearance about twofold, resulting in a decrease in plasma levels of 45-60%. When carbamazepine, phenytoin or another inducer of drug metabolism (such as rifampicin) is added to mirtazapine therapy, the mirtazapine dose may have to be increased. If treatment with an inducer is stopped, mirtazapine dose may have to be decreased.
In in vivo interaction studies, mirtazapine did not influence the pharmacokinetics of paroxetine (CYP2D6 substrates), carbamazepine or phenytoin (CYP3A4 inducers), amitriptyline or cimetidine.
In a mirtazapine and lithium interaction study, the steady-state pharmacokinetics of lithium were not affected by coadministration of a single oral dose of 30 mg of mirtazapine. Correspondingly, the single dose pharmacokinetics of mirtazapine were not affected by the lithium steady state.

Pharmacodynamic interactions.

Mirtazapine should not be administered concomitantly with MAO inhibitors or within two weeks after discontinuation of MAO inhibitor therapy. In the opposite way about two weeks should pass before patients treated with mirtazapine should be treated with MAO inhibitor (see Section 4.3 Contraindications). In addition, as with SSRIs, coadministration with other serotonergic active substances (L-tryptophan, triptans, tramadol, linezolid, methylene blue, SSRIs, venlafaxine, lithium and St. John's wort (Hypericum perforatum) preparations) may lead to an incidence of serotonin associated effects (see Section 4.4 Special Warnings and Precautions for Use). Caution should be advised and a closer clinical monitoring is required when these active substances are combined with mirtazapine.
Mirtazapine may potentiate the sedative effects of benzodiazepines and other sedatives (especially antipsychotics, antihistamine H1-antagonists, opioids). Caution should be taken when these drugs are prescribed together with Axit.
Mirtazapine may potentiate the central nervous dampening action of alcohol. Patients using mirtazapine should, therefore, be advised to avoid alcohol during tasks which require concentration and alertness.
Mirtazapine dosed at 30 mg daily caused a small but statistically significant increase of the international normalised ratio (INR) in subjects treated with warfarin. Both at continuing stable doses and higher doses of mirtazapine, a more pronounced effect cannot be excluded. It is advisable to monitor the prothrombin time more carefully in case of concomitant treatment of warfarin with mirtazapine.
The risk of QT prolongation and/or ventricular arrhythmias (e.g. torsades de pointes) may be increased with concomitant use of medicines which prolong the QTc interval (e.g. some antipsychotics and antibiotics) and in case of mirtazapine overdose.
From post-marketing experience it appears that serotonin syndrome occurs very rarely in patients treated with mirtazapine in combination with SSRIs or venlafaxine. If the combination is considered therapeutically necessary, dosage changes should be made with caution and there should be adequate close monitoring for early signs of serotonergic overstimulation.

4.6 Fertility, Pregnancy and Lactation

Effects on fertility.

In a fertility study in rats, mirtazapine was given at doses up to 100 mg/kg (about 20 times the recommended human dose of 45 mg on a mg/m2 basis). The drug did not affect mating and conception but oestrus cycling was disrupted at doses that were three or more times the recommended human dose of 45 mg on a mg/m2 basis.
(Category B3)
There are insufficient clinical data to assess the possible effect of mirtazapine on pregnancy.
Oral dosing of pregnant rats with mirtazapine at 100 mg/kg/day was associated with a reduction in survival of the offspring, and an increased incidence of postnatal mortality. Mirtazapine was not teratogenic in rats at these dose levels, or in rabbits at oral doses up to 40 mg/kg/day.
Although studies in animals have not shown any teratogenic effects of toxicological significance the safety of mirtazapine in human pregnancy has not been established. Epidemiological data have suggested that the use of SSRIs in pregnancy, particularly use in late pregnancy, may increase the risk of persistent pulmonary hypertension of the newborn (PPHN). Although no studies have investigated the association of PPHN to mirtazapine treatment, this potential risk cannot be ruled out taking into account the related mechanism of action (increase in serotonin concentrations). Mirtazapine should be used during pregnancy only if it is clearly needed. Women of childbearing potential should employ an adequate method of contraception if taking mirtazapine.
 Although animal experiments show that mirtazapine is excreted only in very small amounts in the milk, postnatal mortality was increased when lactating rats were given mirtazapine orally at 100 mg/kg/day.
The use of mirtazapine in breastfeeding mothers is not recommended since no human data in breast milk are available.

4.7 Effects on Ability to Drive and Use Machines

Mirtazapine may impair concentration and alertness (more commonly in the initial phase of treatment). Patients treated with mirtazapine should be cautioned about operating hazardous machinery, including motor vehicles, until they are reasonably certain that the treatment does not affect them adversely.

4.8 Adverse Effects (Undesirable Effects)

Clinical trials.

Depressed patients display a number of symptoms that are associated with the illness itself. It is, therefore, sometimes difficult to ascertain which symptoms are a result of the illness itself and which are a result of treatment with mirtazapine. See Table 1.

Post-marketing reports.

Skin and subcutaneous tissue disorders.

Stevens-Johnson syndrome, dermatitis bullous, erythema multiforme, toxic epidermal necrolysis, rash (including erythematous and maculopapular), rare cases of increased sweating, alopecia, pruritus and urticaria; drug reaction with eosinophilia and systemic symptoms (DRESS) (frequency not known).

Musculoskeletal, connective tissue and bone disorders.

Back pain, arthralgia, myalgia, rhabdomyolysis.

Nervous system disorders.

Amnesia, lethargy, dysarthria, serotonin syndrome, somnolence (i.e. drowsiness, sedation), impaired concentration, dizziness, paraesthesia, headache, hyperkinesia, rare cases of cerebrovascular disorder, convulsions, tremor and myoclonus, movement disorders**. Very rare cases of oral paraesthesia.

Psychiatric disorders.

Suicidal ideation***, suicidal behaviour***, confusion, agitation, aggression, paroniria, less common or rare occurrences of nightmares/vivid dreams, hallucination, mania, depression, anxiety*, insomnia* and psychomotor restlessness** and somnambulism.

Gastrointestinal disorders.

Constipation, vomiting, pancreatitis, increased salivation, nausea, diarrhoea, dry mouth, less common or rare cases of stomatitis, very rare cases of oral hypoaesthesia and mouth oedema.

Hepatobiliary disorders.

Hepatic function abnormal, elevated hepatic enzymes or transaminases, rare cases of jaundice, hepatitis.

Metabolism and nutrition disorders.

Hyponatraemia, increased appetite, rare cases of hypercholesterolaemia, hyperlipidaemia.

Cardiac disorders.

Tachycardia, palpitations, rare cases of arrhythmia, myocardial infarction, chest pain.

Vascular disorders.

Hypotension, dependent oedema, hypertension, orthostatic hypotension, rare cases of thromboembolic disorder, pulmonary embolism.

Blood and lymphatic system disorders.

Leukopenia, granulocytopoenia, rare cases of agranulocytosis (see Section 4.4 Special Warnings and Precautions for Use), rare cases of thrombocytopaenia, pancytopenia, anaemia, aplastic anaemia, eosinophilia and coagulation disorder.

Endocrine disorders.

Hyperprolactinaemia (and related symptoms e.g. galactorrhoea and gynaecomastia).

Renal and urinary disorders.

Rare cases of urinary retention.

Reproductive system and breast disorders.

Priapism.

General disorders and administration site conditions.

Oedema including generalised, peripheral and face oedema; fatigue/asthenia, rare cases of pyrexia, syncope, chest pain and drug withdrawal symptoms.

Investigations.

Increase in gamma-glutamyltransferase levels, hypertriglyceridaemia, weight gain, increased creatine kinase.

Eye disorders.

Very rare cases of glaucoma.
*Upon treatment with antidepressants in general, anxiety and insomnia (which may be symptoms of depression) can develop or become aggravated. Under mirtazapine treatment, development or aggravation of anxiety and insomnia has been reported very rarely.
**Including akathisia, hyperkinesia.
***Cases of suicidal ideation and suicidal behaviours have been reported during mirtazapine therapy or early after treatment discontinuation (see Section 4.4 Special Warnings and Precautions for Use).

Reporting suspected adverse effects.

Reporting suspected adverse reactions after registration of the medicinal product is important. It allows continued monitoring of the benefit-risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions at www.tga.gov.au/reporting-problems.

4.9 Overdose

Post-marketing experience concerning overdose with mirtazapine alone indicates that symptoms are usually mild. The symptoms of overdose are an exaggeration of the pharmacological action of mirtazapine and may include symptoms such as dizziness, impaired consciousness (confusion, disorientation, stupor, coma), agitation, tremor, tachycardia and hyper- and hypotension.
As with all overdose attempts, the possibility of multiple drug ingestion should be borne in mind. As with antidepressants in general, serious outcomes, including fatalities, are possible at dosages much higher that the therapeutic dose, especially with mixed overdoses. In these cases, QT prolongation and torsades de pointes have also been reported.

Overdose management.

Cases of overdose should receive appropriate symptomatic and supportive therapy for vital functions. ECG monitoring should be undertaken.
For information on the management of overdose, contact the Poisons Information Centre on 13 11 26 (Australia).

5 Pharmacological Properties

5.1 Pharmacodynamic Properties

Axit (mirtazapine) is an antidepressant, which can be given as treatment for episodes of major depression. The presence of symptoms such as anhedonia, psychomotor inhibition, sleep disturbances (early wakening) and weight loss increase the chance of a positive response. Other symptoms are loss of interest, suicidal thoughts and changes in mood (better in the evening than in the morning). Mirtazapine begins to exert its effect generally after 1 to 2 weeks of treatment.
The results of three pivotal placebo controlled double blind studies (161 patients received placebo and 161 patients received mirtazapine) have demonstrated that mirtazapine is statistically significantly more effective than placebo in the short-term treatment of a major depressive episode; the efficacy is maintained during continuation treatment with mirtazapine. The efficacy of mirtazapine has been found to be comparable to several standard antidepressant agents (amitriptyline, doxepin, clomipramine). As of 1996 no comparative studies have been performed with selective serotonin reuptake inhibitors (SSRIs) or mianserin (to which mirtazapine has structural similarities).

Mechanism of action.

Mirtazapine is an antagonist of central α2-auto and heteroadrenoreceptors which causes an increase in both noradrenaline and serotonin release. The effect of released serotonin is exerted specifically via 5HT1 (hydroxytryptamine1) type receptors, because 5HT2 and 5HT3 type receptors are specifically blocked by mirtazapine. Mirtazapine is accordingly a noradrenergic and specific serotonergic antidepressant. The α2, 5HT2 and 5HT3-antagonistic effects all contribute to the antidepressant profile of mirtazapine. The presentation of mirtazapine is as a racemate. The two enantiomers contribute differently to its pharmacological profile. The α2 and 5HT2-receptor blocking activity is contained in the (S)+ enantiomer, whereas the 5HT3-receptor blocking activity is contained in the (R)-enantiomer. The presence of both enantiomers is, therefore, considered to be essential for the antidepressant activity of mirtazapine. In one study, there was no efficacy difference indicated between the two enantiomers, despite their different receptor affinities.
Mirtazapine is generally well tolerated. The histamine H1-antagonistic activity of mirtazapine may cause a degree of sedation in the first weeks of treatment. It has practically no anticholinergic activity. Mirtazapine has been associated with acute postural hypotension in healthy volunteer studies but this occurred rarely in patient studies (see Section 4.8 Adverse Effects (Undesirable Effects)).

Clinical trials.

Several placebo controlled double blind studies have demonstrated that mirtazapine is statistically significantly more effective than placebo in the short-term treatment of a major depressive episode; the efficacy is maintained during continuation treatment with mirtazapine.

Active controlled studies.

The efficacy of mirtazapine has been found to be comparable to several standard antidepressant agents (amitriptyline, doxepin, clomipramine). In addition, eleven six or eight week studies and a 24 week study have been performed in moderately to severely depressed patients in which efficacy and tolerability of mirtazapine were compared to selective serotonin reuptake inhibitors (SSRIs) (four versus fluoxetine, three versus paroxetine, two versus sertraline, two versus fluvoxamine and one versus citalopram). The primary efficacy parameters in these studies were:
change from baseline on HAM-D total score (Hamilton depression rating scale, 17 items) (seven studies);
proportion or number of HAM-D 50% responders (three studies);
change from baseline on MADRAS total score (Montgomery-Asberg depression rating scale, ten items) (one study);
VAMRS six items (Visual Analogue Mood Rating Scale) (one study). Change in HAM-D (12 items) total score was a secondary parameter in this study.
On an intention to treat basis, a total of 1,402 patients were treated with mirtazapine and 1,405 patients were treated with the comparator. In all twelve studies, mirtazapine proved to be at least comparable in efficacy to the SSRIs. In eleven of these studies, statistically significant greater reductions in HAM-D or MADRS total scores and more responders were observed in the mirtazapine groups at one or more time points in the first four weeks.
A meta-analysis of these twelve studies provides further comparison of the onset of efficacy of mirtazapine relative to the SSRIs studied. The primary efficacy parameter for this meta-analysis was time to first 50% reduction on recalculated HAM-D total score (17 items) or recalculated MADRS total score (ten items). There were also a number of secondary parameters which are identified in Tables 2 and 3. Table 2 provides an analysis of the relative event rates (estimated hazard ratios) for various depression parameters limited to the first three treatment weeks for the occurrence of the event and the entire six to eight week study period to define whether the event was sustained or not. The increased hazard ratios demonstrate that the probability at any time of first response (50% or more score reduction), remission, sustained response or sustained remission was consistently and significantly greater among mirtazapine treated than SSRI treated patients, indicating an earlier onset of efficacy. The statistically earlier onset of action observed with mirtazapine may not necessarily translate into a meaningful clinical benefit for an individual patient. Table 3 presents the proportions of HAM-D responders and HAM-D/MADRS remitters at the various time points during treatment. At most time points there were significantly more responders and remitters among mirtazapine treated patients than among SSRI treated patients.
Some secondary parameter results have been excluded from Table 3. These were number of:
50% Bech responders;
50% HAM-D factor I anxiety/ somatisation responders;
50% HAM-D factor V retardation responders;
50% HAM-D factor VI sleep disturbance responders;
HAM-D item depressed mood responders (= 0 or < 2);
HAM-D item suicide or MADRS item suicidal thoughts (= 0 or < 2).
Statistically significant differences favouring mirtazapine were observed for HAM-D factors V and VI at week 1 to 6 time points. Statistically significant differences favouring mirtazapine were observed for HAM-D factor I at week 1 to 4 time points. A statistically significant difference was observed in favour of mirtazapine for Bech responders at the week 2 time point. There were no other statistically significant differences.
An eight week comparative study was performed to compare the antidepressant efficacy and tolerability of mirtazapine and venlafaxine in the treatment of 157 hospitalised patients with severe depression with melancholic features (HAM-D total score > 25). In this study, mirtazapine and venlafaxine were equally effective in reducing symptoms of depression and improving quality of life during treatment.

Long-term maintenance of efficacy and relapse prevention.

The long-term maintenance of antidepressant efficacy of mirtazapine was originally established in three active controlled and active/placebo controlled studies with treatment periods up to 24 months (amitriptyline as active). Long-term maintenance of efficacy was also confirmed in extension phases of three SSRI comparator studies, a 24 week paroxetine comparator study and one venlafaxine comparator study. Additionally, a multicentre, long-term, double blind, placebo controlled study of relapse prevention in male and female outpatients diagnosed with moderate to severe recurrent major depression (protocol 003041) was performed. In the initial open label phase of the study, 421 patients were treated with mirtazapine for 8 to 12 weeks. Patients remitting after 8 to 12 weeks were randomised into the 40 week, double blind, relapse prevention phase of the study. The remitted patients were randomised to either mirtazapine at the final titrated dose they received during the open label phase or placebo (79 to mirtazapine and 81 to placebo). The results of the trial showed that mirtazapine reduced the risk of relapse by more than half (15/76 = 19.7% relapsed on mirtazapine versus 35/80 = 43.8% relapsed on placebo, p = 0.001). The treatment was well tolerated with dropouts due to adverse events being 11.4% (9/79) from the mirtazapine group and 2.5% (2/81) from the placebo group. Further discontinuation details are summarised in Table 4.

Elderly.

The efficacy and tolerability in elderly patients were investigated in three randomised controlled trials. In two six week trials with a total of 270 patients aged over 55 years (mean age 70 and 62 years, respectively), mirtazapine was at least as effective as amitriptyline and all treatments were well tolerated. In an eight week study in 255 patients aged 65 and over (mean age 72 years) comparing mirtazapine with paroxetine, mean HAM-D scores were similar at endpoint but lower for mirtazapine in the first three weeks, although only at day 14 was the difference statistically significant. Total discontinuation rates were similar (22.7% for mirtazapine versus 31.0% for paroxetine), although discontinuation due to adverse events was lower with mirtazapine than paroxetine (14.8% versus 26.2%) and discontinuation due to lack of efficacy higher (3.9% versus 0%).

5.2 Pharmacokinetic Properties

Absorption.

After oral administration of mirtazapine tablets, the active constituent mirtazapine is rapidly and well absorbed (bioavailability approximately 50%), reaching peak plasma levels after about 2 hours. Food intake has no clinically significant influence on the pharmacokinetics of mirtazapine.

Distribution.

Binding of mirtazapine to plasma proteins is approximately 85%. The half-life of elimination is 20 to 40 hours; longer half-lives, up to 65 hours, have occasionally been recorded and shorter half-lives have been seen in young men. The half-life of elimination is sufficient to justify once a day dosing. Steady state is reached after 3 to 6 days, after which there is no further accumulation. Mirtazapine displays linear pharmacokinetics within the recommended dose range.

Metabolism.

In vitro data from human liver microsomes indicate that cytochrome P450 enzymes CYP2D6 and CYP1A2 are involved in the formation of the 8-hydroxy metabolite of mirtazapine, whereas CYP3A4 is considered to be responsible for the formation of the N-demethyl and N-oxide metabolites.
The presentation of mirtazapine is as a racemate. It is not known whether first-pass extraction of the drug is stereoselective but it is known that the clearance of the two enantiomers is by different metabolic processes.

Excretion.

Mirtazapine is extensively metabolised and its metabolites are eliminated via the urine and faeces within four days. Major pathways of biotransformation are demethylation and oxidation, followed by conjugation. The demethyl metabolite is pharmacologically active and appears to have the same pharmacokinetic profile as the parent compound.

Pharmacokinetics in special populations.

Renal and/or hepatic impairment.

The clearance of mirtazapine may be decreased as a result of renal or hepatic insufficiency. Mirtazapine is substantially excreted by the kidney (75%) and the risk of decreased clearance of this drug is greater in patients with impaired renal function (see Section 4.2 Dose and Method of Administration).

Geriatric.

The recommended dosage regimen is the same as for adults. Increases should be monitored carefully (see Section 4.2 Dose and Method of Administration).

Children and adolescents.

The safety and effectiveness of mirtazapine has not been established in children and adolescents and therefore should not be prescribed in these patient groups (see Section 4.4 Special Warnings and Precautions for Use, Paediatric use).

Sex.

The half-life of elimination of mirtazapine ranged from 20 to 40 hours, longer half-lives up to 65 hours have occasionally been recorded and shorter half-lives have been seen in young men.

Race.

There is no information available regarding the effect of race on the pharmacokinetics of mirtazapine.

5.3 Preclinical Safety Data

Genotoxicity.

Since the only tumours found in carcinogenicity studies with mice and rats were considered to be species specific, nongenotoxic responses associated with long-term treatment with hepatic enzyme inducers, mirtazapine is not expected to possess carcinogenic potential at therapeutic dosages in the clinic. Mirtazapine was not genotoxic in a series of tests for gene mutation and chromosomal and DNA damage.

Carcinogenicity.

An eighteen month carcinogenicity study in mice showed an increase in the development of hepatic tumours in males after mirtazapine treatment at oral doses of 20 mg/kg/day and above. In a two year carcinogenicity study in rats, oral doses of mirtazapine greater than 20 mg/kg/day were associated in males with an increased incidence of thyroid follicular cell adenomas and carcinomas.

6 Pharmaceutical Particulars

6.1 List of Excipients

Core tablet: maize starch, hyprolose, magnesium stearate, colloidal anhydrous silica, lactose.
Coating layer: 15 mg: Opadry II complete film coating system 39F52901 yellow (Proprietary Ingredient Number: 10164).
30 mg: Opadry buff OY-LS-37200 (Proprietary Ingredient Number: 3249).
45 mg: Opadry white OY-LS-28908 (Proprietary Ingredient Number: 2596).

6.2 Incompatibilities

Incompatibilities were either not assessed or not identified as part of the registration of this medicine.

6.3 Shelf Life

In Australia, information on the shelf life can be found on the public summary of the Australian Register of Therapeutic Goods (ARTG). The expiry date can be found on the packaging.

6.4 Special Precautions for Storage

Store below 30°C.

6.5 Nature and Contents of Container

Container type: blister pack (PVC/PVDC/Al).
Pack sizes: 15 mg: blister pack - 5, 30, 60 and 90.
30 mg: blister pack - 5 and 30.
45 mg: blister pack - 5 and 30.
Some strengths, pack sizes and/or pack types may not be marketed.

6.6 Special Precautions for Disposal

In Australia, any unused medicine or waste material should be disposed of by taking it to your local pharmacy.

6.7 Physicochemical Properties

Chemical structure.

Mirtazapine is a tetracyclic piperazinoazepine analogue of mianserin, a chemical structure unrelated to tricyclic antidepressants, monoamine oxidase inhibitors or selective serotonin reuptake inhibitors. Mirtazapine is a white to creamy white crystalline powder which is slightly soluble in water.
Chemical name: (±)-1,2,3,4,10,14b- hexahydro-2-methyl-pyrazino [2,1-a]pyrido[2,3-c][2]benzazepine.
Molecular formula: C17H19N3.
Molecular weight: 265.36.

CAS number.

61337-67-5.

7 Medicine Schedule (Poisons Standard)

S4 (Prescription Only Medicine).

Summary Table of Changes