Consumer medicine information

Zithro

Azithromycin

BRAND INFORMATION

Brand name

Zithro

Active ingredient

Azithromycin

Schedule

S4

 

Consumer medicine information (CMI) leaflet

Please read this leaflet carefully before you start using Zithro.

SUMMARY CMI

ZITHRO

Consumer Medicine Information (CMI) summary

The full CMI on the next page has more details. If you are worried about using this medicine, speak to your doctor or pharmacist.

1. Why am I taking ZITHRO?

ZITHRO contains the active ingredient azithromycin dihydrate. ZITHRO is used to treat infections in different parts of the body caused by bacteria, such as chlamydia. Azithromycin belongs to a group of medicines called macrolide antibiotics.

For more information, see Section 1. Why am I taking ZITHRO? in the full CMI.

2. What should I know before I take ZITHRO?

Do not use if you have ever had an allergic reaction to ZITHRO or any of the ingredients listed at the end of the CMI.

Talk to your doctor if you have any other medical conditions, take any other medicines, or are pregnant or plan to become pregnant or are breastfeeding.

For more information, see Section 2. What should I know before I take ZITHRO? in the full CMI.

3. What if I am taking other medicines?

Some medicines may interfere with ZITHRO and affect how it works.

A list of these medicines is in Section 3. What if I am taking other medicines? in the full CMI.

4. How do I take ZITHRO?

  • Your doctor will tell you how much of this medicine you should take, depending on your condition and whether you are taking any other medicines.
  • The usual dose to treat chlamydia is two 500 mg tablets taken as a single dose. For other infections azithromycin is usually taken once a day. Sometimes the dose is taken once a week. Your doctor will decide the right dose for you.

More instructions can be found in Section 4. How do I take ZITHRO? in the full CMI.

5. What should I know while taking ZITHRO?

Things you should do
  • Remind any doctor, dentist or pharmacist you visit that you are taking ZITHRO.
  • If you become pregnant while taking ZITHRO, tell your doctor immediately.
  • If your infection does not improve within a few days, or if your symptoms become worse, tell your doctor.
  • If you get severe diarrhoea, tell your doctor immediately. Do this even if it occurs several weeks after you have stopped taking ZITHRO.
  • If you get a sore, white mouth or tongue while taking or soon after stopping ZITHRO, tell your doctor. Also tell your doctor if you get vaginal itching or discharge.
  • Protect your skin when you are in the sun, especially between 10am and 3pm.
Things you should not do
  • Do not stop taking ZITHRO or change the dosage without first checking with your doctor.
  • If you do not complete the full course, all the organisms causing your infection may not be killed.
Driving or using machines
  • This medicine is not expected to affect your ability to drive a car or operate machinery.
Looking after your medicine
  • Keep your medicine in a cool dry place where the temperature stays below 25°C.
  • Do not store your medicine, or any other medicine, in the bathroom or near a sink. Do not leave it on a window sill or in the car.

For more information, see Section 5. What should I know while taking ZITHRO? in the full CMI.

6. Are there any side effects?

There are a number of side effects associated with ZITHRO. It is important to be aware of them so that you can identify any symptoms if they occur. For more information, including what to do if you have any side effects, see Section 6. Are there any side effects? in the full CMI.



FULL CMI

ZITHRO

Active ingredient: azithromycin dihydrate

Consumer Medicine Information (CMI)

This leaflet provides important information about taking ZITHRO. You should also speak to your doctor or pharmacist if you would like further information or if you have any concerns or questions about taking ZITHRO.

Where to find information in this leaflet:

1. Why am I taking ZITHRO?
2. What should I know before I take ZITHRO?
3. What if I am taking other medicines?
4. How do I take ZITHRO?
5. What should I know while taking ZITHRO?
6. Are there any side effects?
7. Product details

1. Why am I taking ZITHRO?

ZITHRO contains the active ingredient azithromycin dihydrate. ZITHRO is an antibiotic, which belongs to a group of medicines called azalides. The azalides are a sub-class of a group of antibiotics called macrolides.

ZITHRO works by killing or stopping the growth of bacteria causing your infection.

ZITHRO will not work against viral infections such as colds or flu.

ZITHRO is used to treat infections in different parts of the body caused by bacteria.

It is commonly used to treat Chlamydia.

ZITHRO is also used to prevent infections by a bacterium called Mycobacterium Avium-intracellulare Complex (MAC) in some people.

ZITHRO is only available with a doctor's prescription.

ZITHRO is not addictive.

2. What should I know before I take ZITHRO?

Warnings

Do not take ZITHRO if:

  • you are allergic to azithromycin dihydrate, macrolide antibiotics (e.g. clarithromycin, erythromycin, roxithromycin, telithromycin) or any of the ingredients listed at the end of this leaflet.
  • Always check the ingredients to make sure you can use this medicine.
  • Symptoms of an allergic reaction may include shortness of breath, wheezing or difficulty breathing, swelling of the face/lips/tongue or to other parts of the body, skin rash, itching or hives.

Check with your doctor if you:

  • have any other medical conditions:
    - any liver problems
    - any kidney problems
    - any heart problems, including heart rhythm abnormalities
    - diabetes, hereditary fructose intolerance, glucose-galactose malabsorption or saccharise-isomaltase deficiency
    - cystic fibrosis
    - muscle weakness
    - low levels of potassium or magnesium in your blood.
  • are pregnant or if you plan to become pregnant or are breastfeeding. Your doctor can discuss with you the risks and benefits involved.
  • take any medicines for any other condition.

During treatment, you may be at risk of developing certain side effects. It is important you understand these risks and how to monitor for them. See additional information under Section 6. Are there any side effects?

Pregnancy and breastfeeding

Check with your doctor if you are pregnant or intend to become pregnant.

Talk to your doctor if you are breastfeeding or intend to breastfeed.

3. What if I am taking other medicines?

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

Some medicines may interfere with ZITHRO and affect how it works.

  • Antacids (medicines used to treat indigestion).
  • Colchicine (a medicine used to treat gout).
  • Coumarin-type oral anti-coagulants (a medicine used to prevent blood clots).
  • Ciclosporin (a medicine used to prevent organ transplant rejection or to treat certain problems with the immune system).
  • Digoxin (a medicine used to treat abnormal heart rhythm or heart failure).
  • Ergot derivatives (such as ergotamine, which is used to treat migraines).
  • Terfenadine or astemizole (medicines used to treat allergies and hay fever).
  • Zidovudine, a medicine used to treat patients with AIDS.
  • Diphenoxylate (Lomotil), a medicine used to treat diarrhoea.
  • Some medicines used to treat heart rhythm problems (heart arrhythmia) such as amiodarone, disopyramide, ibutilide and sotalol.
  • Antipsychotic medicines used to treat schizophrenia or bipolar mania such as haloperidol, quetiapine and risperidone.
  • Medicines used to treat depression (antidepressants) such as fluoxetine, sertraline and venlafaxine.
  • Fluoroquinolone antibiotics such as ciprofloxacin, lomefloxacin, moxifloxacin and norfloxacin.

These medicines may be affected by ZITHRO or may affect how well it works. You may need different amounts of your medicines, or you may need to take different medicines.

Check with your doctor or pharmacist if you are not sure about what medicines, vitamins or supplements you are taking and if these affect ZITHRO.

Talk to your doctor about the need for additional contraception while taking ZITHRO.

Some antibiotics may decrease the effectiveness of some birth control pills, although this has not been shown with ZITHRO.

4. How do I take ZITHRO?

How much to take

  • Your doctor will tell you how much of this medicine you should take, depending on your condition and whether you are taking any other medicines.
  • The usual dose to treat chlamydia is two 500 mg tablets taken as a single dose.
  • For other infections azithromycin is usually taken once a day. Sometimes the dose is taken once a week. Your doctor will decide the right dose for you.

When to take ZITHRO

  • ZITHRO should be taken at about the same time each day.
  • Taking it at the same time each day will have the best effect. It will also help you remember when to take it.
  • This medicine may be taken with or without food.

If you forget to take ZITHRO

If you are taking your medicine for three days or longer and you miss a dose, take it as soon as you remember (within a 24-hour period), then continue as normal.

Do not take a double dose to make up for the dose you missed.

This may increase the chance of you experiencing side effects.

If you are not sure what to do, check with your doctor or pharmacist.

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

If you take too much ZITHRO

If you think that you have used too much ZITHRO, you may need urgent medical attention.

You should immediately:

  • phone the Poisons Information Centre
    (by calling 13 11 26), or
  • contact your doctor, or
  • go to the Emergency Department at your nearest hospital.

You should do this even if there are no signs of discomfort or poisoning.

If you take too many tablets, you may get an upset stomach, diarrhoea or skin rashes.

5. What should I know while taking ZITHRO?

Things you should do

If the symptoms of your infection do not improve within a few days, or if they become worse, tell your doctor.

If you are about to start any new medicines, tell your doctor and pharmacist that you are taking ZITHRO.

Remind any doctor, dentist or pharmacist you visit that you are using ZITHRO.

Protect your skin when you are in the sun, especially between 10am and 3pm.

Some macrolide antibiotics may cause your skin to be more sensitive to sunlight than it is normally. Exposure to sunlight may cause a skin rash, itching, redness or severe sunburn.

If outdoors, wear protective clothing and use a 30+ sunscreen. If your skin does appear to be burning tell your doctor immediately.

Call your doctor straight away if:

  • you get severe diarrhoea, tell your doctor, pharmacist or nurse immediately. Do this even if it occurs several weeks after ZITHRO has been stopped.
    Diarrhoea may mean that you have a serious condition affecting your bowel. You may need urgent medical care. Do not take any diarrhoea medicine without first checking with your doctor.
  • you get a sore, white mouth or tongue while taking, or soon after stopping ZITHRO, tell your doctor. Also tell your doctor if you get vaginal itching or discharge.
    This may mean you have a yeast infection called thrush. Sometimes the use of ZITHRO allows yeast to grow and the above symptoms to occur. ZITHRO does not work against yeast.
  • you become pregnant while taking ZITHRO.
  • during treatment with ZITHRO your baby develops irritability with feeding or starts vomiting. This may be a sign of a stomach disorder in the infant.

Things you should not do

  • Do not stop taking ZITHRO or lower the dosage without checking with your doctor.
    If you do not complete the full course prescribed by your doctor, all the organisms causing your infection may not be killed. These organisms may continue to grow and multiply so that your infection may not clear completely or may return.
  • Do not give ZITHRO to anyone else, even if they have the same condition as you.
  • Do not use ZITHRO to treat any other medical complaints unless your doctor tells you to.

Driving or using machines

This medicine is not expected to affect your ability to drive a car or operate machinery.

Looking after your medicine

  • Keep your medicine in the pack until it is time to take it. If you take your medicine out of its pack it may not keep well.
  • Keep your medicine in a cool dry place where the temperature stays below 25°C.
  • Store it in a cool dry place away from moisture, heat or sunlight; for example, do not store it:
    - in the bathroom or near a sink, or
    - in the car or on window sills.
    Heat and dampness can 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.

Getting rid of any unwanted medicine

If you no longer need to use this medicine or it is out of date, take it to any pharmacy for safe disposal.

Do not use this medicine after the expiry date.

6. Are there any side effects?

All medicines can have side effects. If you do experience any side effects, most of them are minor and temporary. However, some side effects may need medical attention.

See the information below and, if you need to, ask your doctor or pharmacist if you have any further questions about side effects.

Less serious side effects

Less serious side effectsWhat to do
  • Oral thrush - white furry, sore tongue and mouth.
  • Vaginal thrush - sore and itchy vagina and/or white discharge.
  • Nausea (feeling sick), loss of appetite, vomiting, stomach pain, indigestion, wind, constipation, diarrhoea.
    Dizziness, headache, spinning sensation.
  • Tiredness, drowsiness, fatigue muscle or joint aches.
  • Hearing loss or ringing in the ears.
  • Altered taste and smell.
Speak to your doctor if you have any of these less serious side effects and they worry you.

Serious side effects

Serious side effectsWhat to do
  • Severe persistent diarrhoea (loose bowel motions).
  • Fast or irregular heartbeat.
  • Symptoms of sunburn such as redness, itching, swelling or blistering which may occur more quickly than normal.
  • Decreased feeling or sensitivity, especially in the skin.
  • Aggressive reaction, nervousness, agitation or anxiety.
  • Bleeding or bruising more easily than normal, reddish or purplish blotches under the skin.
  • Signs of frequent or worrying infections such as fever, severe chills, sore throat or mouth ulcers.
  • Blood in the urine or bowel motions.
  • Severe upper stomach pain, often with nausea and vomiting.
Call your doctor straight away, or go straight to the Emergency Department at your nearest hospital if you notice any of these serious side effects.

Very serious side effects

Very serious side effectsWhat to do
  • Shortness of breath, wheezing or difficulty breathing; swelling of the face, lips, tongue, throat or other parts of the body; rash, itching or hives on the skin (signs of an allergic reaction).
  • Blisters or ulcers on the skin, in the mouth or airways that may occur after a period of fever.
  • Diarrhoea, usually with blood and mucus, stomach pain and fever.
  • Yellowing of the eyes or skin, also called jaundice.
  • Chest pain.
  • Convulsions (fits).
Call your doctor straight away, or go straight to the Emergency Department at your nearest hospital if you notice any of these very serious side effects.

Tell your doctor or pharmacist if you notice anything else that may be making you feel unwell.

Other side effects not listed here may occur in some people.

Reporting side effects

After you have received medical advice for any side effects you experience, you can report side effects to the Therapeutic Goods Administration online at www.tga.gov.au/reporting-problems. By reporting side effects, you can help provide more information on the safety of this medicine.

Always make sure you speak to your doctor or pharmacist before you decide to stop taking any of your medicines.

7. Product details

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

What ZITHRO contains

Active ingredient
(main ingredient)		Azithromycin dihydrate
Other ingredients
(inactive ingredients)
  • pregelatinised maize starch,
  • crospovidone,
  • calcium hydrogen phosphate,
  • sodium lauryl sulfate,
  • magnesium stearate,
  • lactose monohydrate,
  • hypromellose,
  • titanium dioxide,
  • triacetin
Potential allergensContains lactose

Do not take this medicine if you are allergic to any of these ingredients.

What ZITHRO looks like

ZITHRO is oblong, biconvex, film coated tablets, scored on one side.

AUST R 241812

Available in blisters of 2, 3 and 15 tablets*

* Not all pack sizes may be available.

Who distributes ZITHRO

Arrotex Pharmaceuticals Pty Ltd
15-17 Chapel Street
Cremorne, VIC 3121
Australia
www.arrotex.com.au

This leaflet was prepared in September 2024.

Published by MIMS October 2024

BRAND INFORMATION

Brand name

Zithro

Active ingredient

Azithromycin

Schedule

S4

 

1 Name of Medicine

Azithromycin dihydrate.

2 Qualitative and Quantitative Composition

Zithro tablets contain azithromycin dihydrate equivalent to 500 mg of azithromycin.

Excipients with known effect.

Lactose monohydrate.
For the full list of excipients, see Section 6.1 List of Excipients.

3 Pharmaceutical Form

Zithro tablets are white, oblong, biconvex, film coated tablets, scored on one side.

4 Clinical Particulars

4.1 Therapeutic Indications

Azithromycin is indicated for use in adults for the treatment of the following infections of mild to moderate severity:

1. Lower respiratory tract infections.

Acute bacterial bronchitis due to Streptococcus pneumoniae, Haemophilus influenzae or Moraxella catarrhalis.
Community acquired pneumonia (CAP) due to Streptococcus pneumoniae or Haemophilus influenzae in patients suitable for outpatient oral treatment.
Community acquired pneumonia caused by susceptible organisms in patients who require initial intravenous therapy. In clinical studies efficacy has been demonstrated against Chlamydia pneumoniae, Haemophilus influenzae, Legionella pneumophila, Moraxella catarrhalis, Mycoplasma pneumoniae, Staphylococcus aureus and Streptococcus pneumoniae.

2. Upper respiratory tract infections.

Acute sinusitis due to Streptococcus pneumoniae or Haemophilus influenzae.
Acute streptococcal pharyngitis.

Note.

Penicillin is the usual drug of choice in the treatment of Streptococcus pyogenes pharyngitis, including the prophylaxis of rheumatic fever. Azithromycin appears to be almost as effective in the treatment of streptococcal pharyngitis. However, substantial data establishing the efficacy of azithromycin in the subsequent prevention of rheumatic fever are not available at present.

3. Uncomplicated skin and skin structure infections.

Uncomplicated infections due to Staphylococcus aureus, Streptococcus pyogenes or Streptococcus agalactiae. Abscesses usually require surgical drainage.

4. Sexually transmitted diseases.

Uncomplicated urethritis and cervicitis due to Chlamydia trachomatis.

Note.

At the recommended dose azithromycin cannot be relied upon to treat gonorrhoea or syphilis. As with other drugs for the treatment of non-gonococcal infections, it may mask or delay the symptoms of incubating gonorrhoea or syphilis. Appropriate tests should be performed for the detection of gonorrhoea or syphilis and treatment should be instituted as required.
Azithromycin is also indicated for the treatment of Chlamydia trachomatis conjunctivitis and trachoma.
Azithromycin is also indicated for the prevention of infection due to Mycobacterium avium-intracellulare complex (MAC) disease, when used as the sole agent or in combination with rifabutin at its approved dose, in adults and children aged more than 12 years with HIV infection and CD4 cell count less than or equal to 75 cells/microliter (see Section 4.4 Special Warnings and Precautions for Use). Disseminated infection due to Mycobacterium avium-intracellulare complex should be excluded by a negative blood culture prior to commencement of therapy.
Azithromycin is indicated for use in children for the treatment of the following infections:

1. Acute streptococcal pharyngitis/tonsillitis.

Note.

Penicillin is the usual drug of choice in the treatment of Streptococcus pyogenes pharyngitis, including the prophylaxis of rheumatic fever. The 20 mg/kg azithromycin dose appears to be as effective as penicillin in the treatment of streptococcal pharyngitis. However, substantial data establishing the efficacy of azithromycin in the subsequent prevention of rheumatic fever are not available at present.

2. Chlamydia trachomatis conjunctivitis and trachoma in children 12 months or older.

4.2 Dose and Method of Administration

Azithromycin should be given as a single daily dose. Tablets may be taken with food.

Adults.

Sexually transmitted uncomplicated urethritis and cervicitis due to Chlamydia trachomatis.

1 g as a single dose.

Conjunctivitis and trachoma due to Chlamydia trachomatis.

1 g either as a single dose or once weekly for up to three weeks (see Section 5.1 Pharmacodynamic Properties, Clinical trials).

Following IV therapy for the treatment of community acquired pneumonia (CAP).

500 mg as a single daily dose to complete a 7 to 10 day course of therapy.

All other indications (including outpatients initiated on oral treatment of CAP due to S. pneumoniae or H. influenzae).

Total dose of 1.5 g given as 500 mg on Day 1, then 250 mg daily on Days 2 to 5 or alternatively as 500 mg daily for 3 days.

Children (powder for oral suspension)#.

Conjunctivitis and trachoma due to Chlamydia trachomatis.

20 mg/kg either as a single dose or once weekly for up to 3 weeks.

Streptococcal pharyngitis and tonsillitis.

10 mg/kg or 20 mg/kg once daily for 3 consecutive days providing a total dose of 30 mg/kg or 60 mg/kg over a 3-day treatment period. Do not exceed a daily dose of 500 mg. For children weighing > 45 kg dose as per adults.
# Azithromycin powder for oral suspension is unavailable in Zithro brand however is available in other brands. Where correct dosing requires oral suspension in paediatric or adult patients, the oral suspension available from other suppliers should be used. Refer to the specific product information for azithromycin oral suspension for guidance on administrations and precautions.

4.3 Contraindications

Azithromycin is contraindicated in patients with known hypersensitivity to azithromycin, erythromycin, any other macrolide or ketolide antibiotic, or to any of the inactive ingredients in the product (see Section 6.1 List of Excipients).

4.4 Special Warnings and Precautions for Use

Use with caution in the following circumstances.

In the treatment of pneumonia, azithromycin has been shown to be safe and effective only in the treatment of community-acquired pneumonia (CAP) of mild severity due to Streptococcus pneumoniae or Haemophilus influenzae in patients appropriate for outpatient oral therapy. Azithromycin should not be used in patients with pneumonia who are judged to be inappropriate for outpatient oral therapy because of moderate to severe illness or risk factors such as any of the following:
patients with cystic fibrosis;
patients with nosocomially acquired infections;
patients with known or suspected bacteraemia;
patients requiring hospital admission;
elderly or debilitated patients;
patients with significant underlying health problems that may compromise their ability to respond to their illness (including immunodeficiency or functional asplenia).

Clostridioides difficile-associated diarrhoea.

Antibiotic associated pseudomembranous colitis has been reported with many antibiotics including azithromycin. A toxin produced by Clostridioides difficile appears to be the primary cause. The severity of the colitis may range from mild to life-threatening. It is important to consider this diagnosis in patients who develop diarrhoea or colitis in association with antibiotic use (this may occur up to several weeks after cessation of antibiotic therapy). Mild cases may respond to drug discontinuation alone. However, in moderate to severe cases appropriate therapy with a suitable oral antibacterial agent effective against C. difficile should be considered. Fluids, electrolytes and protein replacement should be provided when indicated. Hypertoxin producing strains of C. difficile cause increased morbidity and mortality, as these infections can be refractory to antimicrobial therapy and may require colectomy.
Drugs which delay peristalsis e.g. opiates and diphenoxylate with atropine (Lomotil) may prolong and/or worsen the condition and should not be used.

Hypersensitivity.

Rare, serious, allergic reactions, including angioedema and anaphylaxis (rarely fatal), and dermatologic reactions including acute generalised exanthematous pustulosis (AGEP), Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN) (rarely fatal); and drug reaction with eosinophilia and systemic symptoms (DRESS) have been reported in patients on azithromycin therapy (see Section 4.3 Contraindications). Despite initially successful symptomatic treatment of the allergic symptoms, when symptomatic therapy was discontinued, the allergic symptoms recurred soon thereafter in some patients without further azithromycin exposure. These patients required prolonged periods of observation and symptomatic treatment. The relationship of these episodes to the long tissue half-life of azithromycin and subsequent prolonged exposure to antigen is unknown at present.
If an allergic reaction occurs, the drug should be discontinued and appropriate therapy should be instituted. Physicians should be aware that reappearance of the allergic symptoms may occur when symptomatic therapy is discontinued.

Prolongation of the QT interval.

Ventricular arrhythmias associated with prolonged QT interval, including ventricular tachycardia and torsades de pointes have been reported with macrolide products including azithromycin. Prescribers should consider the risk of QT prolongation (which can be fatal) when weighing the risks and benefits of azithromycin for at-risk groups including:
patients predisposed to QT interval prolongation;
patients taking other medications known to prolong the QT interval such as antiarrhythmics of classes IA and III; antipsychotic agents; antidepressants; and fluoroquinolones;
patients with electrolyte disturbance, particularly in cases of hypokalaemia and hypomagnesemia;
patients with clinically relevant bradycardia, cardiac arrhythmia or cardiac insufficiency;
elderly patients, as they may be more susceptible to drug-associated effects on the QT interval.

Cardiovascular death.

Some observational studies have shown an approximately two-fold increased short-term potential rare risk of acute cardiovascular death in adults exposed to azithromycin relative to other antibacterial drugs, including amoxicillin. The data in these observational studies are insufficient to establish or exclude a causal relationship between acute cardiovascular death and azithromycin use. This potential risk was noted to be greater during the first five days of azithromycin use. In patients whose medical history and/or on-going medical treatments place them at high risk for a prolonged QTc, consider performing a screening ECG. Consider balancing this potential risk with treatment benefits when prescribing Zithro.

Myasthenia gravis.

Exacerbations of symptoms of myasthenia gravis have been reported in patients receiving azithromycin therapy.

Ergot derivatives.

In patients receiving ergot derivatives, ergotism has been precipitated by co-administration of some macrolide antibiotics. There are no data concerning the possibility of an interaction between ergot and azithromycin. However, because of the theoretical possibility of ergotism, Zithro and ergot derivatives should not be co-administered.

Superinfection.

As with any antibiotic preparation, observation for signs of superinfection with non-susceptible organisms, including fungi, is recommended.

Other.

The majority of cases of disseminated Mycobacterium avium complex infection occur in patients with CD4 counts below 50 cells/microliter. Some authorities recommend delay of initiation of prophylaxis until the cell count has fallen to 50 cells/microliter.
No evidence exists from formal studies to determine the need for, and frequency of, repeat dosing in the treatment of trachoma.

Use in hepatic impairment.

No dose adjustment is recommended for patients with mild to moderate hepatic impairment. Nonetheless, since liver is the principal route of elimination for azithromycin, the use of azithromycin should be undertaken with caution in patients with significant hepatic disease (see Section 5.2 Pharmacokinetic Properties).
Abnormal liver function, hepatitis, cholestatic jaundice, hepatic necrosis, and hepatic failure have been reported, some of which have resulted in death. Discontinue azithromycin immediately if signs and symptoms of hepatitis occur.

Use in renal impairment.

No dose adjustment is needed in patients with GFR 10 - 80 mL/min. After oral administration of a single dose of azithromycin 1 g in subjects with severe renal impairment GFR < 10 mL/min, mean AUC0-120 and mean Cmax were increased by approximately 30% and 60%, respectively, when compared to subjects with GFR > 80 mL/min. Caution should be exercised when azithromycin is administered to patients with GFR < 10 mL/min.

Use in the elderly.

See Section 5.2 Pharmacokinetic Properties.

Paediatric use.

Infantile hypertrophic pyloric stenosis (IHPS) has been reported following the use of azithromycin in neonates (treatment up to 42 days of life). Parents and caregivers should be informed to contact their physician if vomiting or irritability with feeding occurs.

Effects on laboratory tests.

There are no reported laboratory test interactions.

4.5 Interactions with Other Medicines and Other Forms of Interactions

Azithromycin does not interact significantly with the hepatic cytochrome P450 system. It is not believed to undergo the pharmacokinetic drug interactions as seen with erythromycin and other macrolides. Hepatic cytochrome P450 induction or inactivation via cytochrome-metabolite complex does not occur with azithromycin.

Drugs that should not be concomitantly administered with azithromycin.

Antacids.

In a pharmacokinetic study investigating the effects of simultaneous administration of antacid with azithromycin, no effect on overall bioavailability was seen although peak serum concentrations were reduced by up to 30%. In patients receiving both azithromycin and antacids, the drugs should not be taken simultaneously.

Ergot.

Due to the theoretical possibility of ergotism, azithromycin and ergot derivatives should not be co-administered (see Section 4.4 Special Warnings and Precautions for Use, Ergot derivatives).

Drugs that require dosage adjustment when administered concomitantly with azithromycin.

Ciclosporin.

In a pharmacokinetic study with healthy volunteers that were administered a 500 mg/day oral dose of azithromycin for 3 days and were then administered a single 10 mg/kg oral dose of ciclosporin, the resulting Cmax and AUC0-5 were found to be significantly elevated. Consequently, caution should be exercised before considering concurrent administration of these drugs. If co-administration of these drugs is necessary, ciclosporin levels should be monitored and the dose adjusted accordingly.

Drugs that have been studied with no clinically significant interaction shown.

Atorvastatin.

Co-administration of atorvastatin (10 mg daily) and azithromycin (500 mg daily) did not alter the plasma concentrations of atorvastatin (based on a HMG-CoA reductase inhibition assay). However, post-marketing cases of rhabdomyolysis in patients receiving azithromycin with statins have been reported.

Carbamazepine.

In a pharmacokinetic interaction study in healthy volunteers, no significant effect was observed on the plasma levels of carbamazepine or its active metabolite in patients receiving concomitant azithromycin.

Cetirizine.

In healthy volunteers, co-administration of a 5-day regimen of azithromycin with cetirizine 20 mg at steady-state resulted in no pharmacokinetic interaction and no significant changes in the QT interval.

Cimetidine.

In a pharmacokinetic study investigating the effects of a single dose of cimetidine, given 2 hours before azithromycin, on the pharmacokinetics of azithromycin, no alteration of azithromycin pharmacokinetics was seen.

Coumarin-type oral anticoagulants.

In a pharmacokinetic interaction study, azithromycin did not alter the anticoagulant effect of a single 15 mg dose of warfarin administered to healthy volunteers. There have been reports received in the post-marketing period of potentiated anticoagulation subsequent to co-administration of azithromycin and coumarin-type oral anticoagulants. Although a causal relationship has not been established, consideration should be given to the frequency of monitoring prothrombin time, when azithromycin is used in patients receiving coumarin-type oral anticoagulants.

Didanosine.

Co-administration of 1200 mg/day azithromycin with 400 mg/day didanosine in 6 HIV-positive subjects for 2 weeks had no effect on the steady state pharmacokinetics of didanosine as compared with placebo.

Efavirenz.

Co-administration of a single dose of 600 mg azithromycin and 400 mg efavirenz daily for 7 days did not result in any clinically significant pharmacokinetic interactions. No dose adjustment is necessary when azithromycin is given with efavirenz.

Fluconazole.

Co-administration of a single dose of 1200 mg azithromycin did not alter the pharmacokinetics of a single dose of 800 mg fluconazole. Total exposure and half-life of azithromycin were unchanged by the co-administration of fluconazole, however, a clinically insignificant decrease in Cmax (18%) of azithromycin was observed. No dose adjustment is necessary when azithromycin is given with fluconazole.

Indinavir.

Co-administration of a single dose of 1200 mg azithromycin had no statistically significant effect on the pharmacokinetics of indinavir administered as 800 mg three times daily for 5 days. No adjustment of the dose is necessary when azithromycin is given with indinavir.

Methylprednisolone.

In a pharmacokinetic interaction study in healthy volunteers, azithromycin had no significant effect on the pharmacokinetics of methylprednisolone.

Midazolam.

In healthy volunteers, co-administration of azithromycin 500 mg/day for 3 days did not cause clinically significant changes in the pharmacokinetics and pharmacodynamics of a single 15 mg dose of midazolam.

Nelfinavir.

Co-administration of 1200 mg azithromycin and nelfinavir at steady state (750 mg three times daily) resulted in increased azithromycin concentrations. No clinically significant adverse effects were observed and no dose adjustment is required.

Rifabutin.

Co-administration of azithromycin and rifabutin did not affect the serum concentrations of either drug. Neutropenia was observed in subjects receiving concomitant treatment with azithromycin and rifabutin. Although neutropenia has been associated with use of rifabutin, a causal relationship to combination with azithromycin has not been established.

Sildenafil.

In normal healthy male volunteers, there was no evidence of an effect of azithromycin (500 mg daily for 3 days) on the AUC and Cmax, of sildenafil or its major circulating metabolite.

Terfenadine, astemizole.

In a study in normal subjects, addition of azithromycin did not result in any significant changes in cardiac repolarisation (QTc interval) measured during the steady state dosing of terfenadine. However, there have been cases reported where the possibility of such an interaction could not be entirely excluded.

Theophylline.

There is no evidence of any pharmacokinetic interaction when azithromycin and theophylline are co-administered to healthy volunteers.

Triazolam.

In 14 healthy volunteers, co-administration of azithromycin 500 mg on Day 1 and 250 mg on Day 2 with 0.125 mg triazolam on Day 2 had no significant effect on any of the pharmacokinetic variables for triazolam compared to triazolam and placebo.

Trimethoprim/sulfamethoxazole.

Co-administration of trimethoprim/sulfamethoxazole DS (160 mg/800 mg) for 7 days with azithromycin 1200 mg on Day 7 had no significant effect on peak concentrations, total exposure or urinary excretion of either trimethoprim or sulfamethoxazole. Azithromycin serum concentrations were similar to those seen in other studies. No dose adjustment is necessary.

Zidovudine.

Single 1000 mg doses and multiple 1200 mg or 600 mg doses of azithromycin did not affect the plasma pharmacokinetics or urinary excretion of zidovudine or its glucuronide metabolite. However, administration of azithromycin increased the concentrations of phosphorylated zidovudine, the clinically active metabolite, in peripheral blood mononuclear cells. The clinical significance of this finding is unclear.

Other interactions.

Digoxin and colchicine.

Some of the macrolide antibiotics including azithromycin have been reported to impair the metabolism of P-glycoprotein substrates such as digoxin and colchicine (in the gut) in some patients and to result in increased serum levels of the P-glycoprotein substrates. In patients receiving concomitant azithromycin, a related azalide antibiotic, and digoxin, the possibility of raised digoxin levels should be borne in mind. During treatment with azithromycin and after discontinuation thereof, clinical monitoring and measurement of serum digoxin levels may be necessary.

4.6 Fertility, Pregnancy and Lactation

Effects on fertility.

In three fertility and general reproduction studies in rats, there was decreased fertility at doses of 20 and 30 mg/kg/day. The clinical significance of this is unknown.
(Category B1)
Azithromycin was not foetotoxic or teratogenic in mice and rats at doses that were moderately maternotoxic (up to 200 mg/kg/day). At 200 mg/kg/day, mouse and rat foetal tissues homogenate concentrations were 5 to 10-fold higher than corresponding maternal plasma concentrations.
There are no adequate and well-controlled studies in pregnant women.
Data exists from published observational studies performed in several countries on exposure to azithromycin during pregnancy, compared to no antibiotic use or use of another antibiotic during the same period.
While most of these studies do not suggest an association with adverse foetal effects such as major congenital malformations or cardiovascular malformations, there is limited epidemiological evidence of an increased risk of miscarriage following azithromycin exposure in early pregnancy.
Azithromycin should only be used during pregnancy if clinically needed and the benefit of treatment is expected to outweigh any small increased risks which may exist.
 Limited information available from published literature indicates that azithromycin is present in human milk. A decision must be made whether to discontinue breast-feeding or to discontinue/abstain from azithromycin therapy, taking into account the benefit of breast-feeding for the child and the benefit of therapy for the woman.

4.7 Effects on Ability to Drive and Use Machines

The effects of this medicine on a person's ability to drive and use machines were not assessed as part of its registration.

4.8 Adverse Effects (Undesirable Effects)

Clinical trials.

In clinical trials, most of the reported adverse events were mild to moderate in severity and were reversible on discontinuation of the drug. Approximately 0.7% of patients discontinued azithromycin therapy because of treatment-related adverse events. Most of the adverse events leading to discontinuation were related to the gastrointestinal tract, e.g. nausea, vomiting, diarrhoea or abdominal pain. Rare, but potentially serious, adverse events were angioedema (1 case) and cholestatic jaundice (1 case).
Hearing impairment has been reported in investigational studies, mainly where higher doses were used, for prolonged periods of time. In those cases where follow-up information was available, the majority of these events were reversible.

Adults.

Multiple-dose regimen. The most frequently reported adverse events in patients receiving the multiple-dose regimen of azithromycin were related to the gastrointestinal system with diarrhoea/loose stools (5%), nausea (3%) and abdominal pain (3%) being the most frequently reported. No other side effects occurred in patients on the multiple-dose regimen with a frequency > 1%.
Side effects that occurred with a frequency of 1% or less included the following:

Allergic.

Rash, photosensitivity, angioedema.

Cardiovascular.

Palpitations, chest pain.

Gastrointestinal.

Dyspepsia, flatulence, vomiting, melaena, cholestatic jaundice.

Genitourinary.

Moniliasis, vaginitis, nephritis.

Nervous system.

Dizziness, headache, vertigo, somnolence.

General.

Fatigue.
Single 1-gram dose regimen. The most frequently reported adverse events in patients receiving a single-dose regimen of 1 gram of azithromycin were related to the gastrointestinal system and were more frequently reported than in patients receiving the multiple-dose regimen. Adverse events that occurred in patients on the single 1-gram dosing regimen of azithromycin with a frequency of 1% or greater included diarrhoea/loose stools (7%), nausea (5%), abdominal pain (5%), vomiting (2%), vaginitis (2%) and dyspepsia (1%).
Laboratory abnormalities. Significant abnormalities (irrespective of drug relationship) occurring during the clinical trials were reported as follows:

Incidence > 1%.

Elevated serum creatine phosphokinase, potassium, ALT (SGPT), GGT and AST (SGOT), lymphocytes and neutrophils; decreased neutrophils.

Incidence < 1%.

Leukopenia, neutropenia, thrombocytopenia; elevated serum alkaline phosphatase, bilirubin, BUN, creatinine, blood glucose, LDH, and phosphate, monocytes, basophils, bicarbonate; decreased sodium, potassium.
When follow-up was provided, changes in laboratory tests appeared to be reversible.
In multiple-dose trials involving > 3000 patients, 3 patients discontinued therapy because of treatment-related liver enzyme abnormalities and 1 patient because of a renal function abnormality. See Table 1.
The most common laboratory test abnormalities were haematological (mainly decreases in haemoglobin and white cell count) and increases in AST and ALT.

Children.

The side effect profile in children is comparable with that of adults. No new adverse events have been reported in children. In the treatment of streptococcal pharyngitis, the 20 mg/kg/day dose is associated with a higher rate of adverse events. These are mainly gastrointestinal and remain mild to moderate.
The following adverse events, where a causal relationship to treatment could not be ruled out, were reported at an occurrence of ≥ 1% (see Table 2):

Post-marketing experience.

In post-marketing experience, the following adverse events have been reported:

Infections and infestations.

Moniliasis and vaginitis.

Blood and lymphatic system disorders.

Thrombocytopenia.

Cardiovascular disorders.

Hypotension; palpitations and arrhythmias including ventricular tachycardia have been reported. There have been rare reports of QT prolongation and torsades de pointes, and cardiovascular death.

Gastrointestinal disorders.

Vomiting/diarrhoea (rarely resulting in dehydration), dyspepsia, pancreatitis, constipation, pseudomembranous colitis, rare reports of tongue discolouration.

General disorders and administration site conditions.

Asthenia, fatigue and malaise.

Hepatobiliary disorders.

Abnormal liver function including hepatitis and cholestatic jaundice, hepatic necrosis and hepatic failure, which have resulted in death.

Immune system disorders.

Anaphylaxis (rarely fatal).

Metabolism and nutritional disorders.

Anorexia.

Musculoskeletal and connective tissue disorders.

Arthralgia.

Nervous system disorders.

Dizziness, convulsions, headache, hyperactivity, hypoesthesia, paraesthesia, somnolence, syncope.

Psychiatric disorders.

Aggressive reaction, nervousness, agitation, anxiety.

Renal and urinary tract disorders.

Acute renal failure, interstitial nephritis.

Skin and subcutaneous tissue disorders.

Allergic reactions including pruritus, rash, photosensitivity, urticaria, oedema, angioedema, serious skin reactions including erythema multiforme, acute generalised exanthematous pustulosis (AGEP), Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), drug reaction with eosinophilia and systemic symptoms (DRESS).

Special senses.

Hearing disturbances and/or impairment including hearing loss, deafness and/or tinnitus, vertigo. Taste/smell perversion and/or loss.

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

Most adverse events experienced in higher than recommended doses are similar in type and may be more frequent than those seen at normal doses. The incidence of tinnitus and ototoxicity is more frequent in overdosage than at normal doses. In the event of overdosage, general symptomatic and supportive measures are indicated as required.
As with many cationic amphiphilic drugs, phospholipidosis has been observed in some tissues of mice, rats and dogs given multiple doses of azithromycin. It has been demonstrated in numerous organ systems in dogs administered doses which, based on pharmacokinetics, are as low as 2-3 times greater than the recommended human dose and in rats at doses comparable to the human dose. This effect is reversible after cessation of azithromycin treatment. The significance of these findings for humans with overdose of azithromycin is unknown.
For information on the management of overdose, contact the Poisons Information Centre on 13 11 26 (Australia).

5 Pharmacological Properties

5.1 Pharmacodynamic Properties

Mechanism of action.

Azithromycin acts by binding to the 50S ribosomal subunit of susceptible organisms, thus, interfering with microbial protein synthesis. Nucleic acid synthesis is not affected.
Microbiology. Azithromycin demonstrates activity in vitro against a wide range of bacteria including:

Gram-positive aerobic bacteria.

Staphylococcus aureus, Streptococcus pyogenes (group A beta-hemolytic streptococci), Streptococcus pneumoniae, alpha-haemolytic streptococci (viridans group) and other streptococci, and Corynebacterium diphtheriae. Azithromycin demonstrates cross-resistance with erythromycin-resistant gram-positive strains, including Streptococcus faecalis (Enterococcus) and to most strains of methicillin-resistant staphylococci.

Gram-negative aerobic bacteria.

Haemophilus influenzae (including beta-lactamase producing Haemophilus influenzae), Haemophilus parainfluenzae, Moraxella catarrhalis, Acinetobacter species, Yersinia species, Legionella pneumophila, Bordetella pertussis, Bordetella parapertussis, Shigella species, Pasteurella species, Vibrio cholerae and parahaemolyticus, Plesiomonas shigelloides. Activities against Escherichia coli, Salmonella enteritidis, Salmonella typhi, Enterobacter species, Aeromonas hydrophila and Klebsiella species are variable and susceptibility tests should be performed. Proteus species, Serratia species, Morganella species, and Pseudomonas aeruginosa are usually resistant.

Anaerobic bacteria.

Bacteroides fragilis and Bacteroides species, Clostridium perfringens, Peptococcus species, Peptostreptococcus species, Fusobacterium necrophorum and Propionibacterium acnes.

Organisms of sexually transmitted diseases.

Azithromycin is active against Chlamydia trachomatis and also shows good activity against Treponema pallidum, Neisseria gonorrhoeae and Haemophilus ducreyi.

Other organisms.

Borrelia burgdorferi (Lyme disease agent), Chlamydia pneumoniae, Mycoplasma pneumoniae, Mycoplasma hominis, Ureaplasma urealyticum, Campylobacter species and Listeria monocytogenes.

Opportunistic pathogens associated with human immunodeficiency virus (HIV) infections.

Mycobacterium avium-intracellulare complex (MAC).
Azithromycin demonstrates activity in vivo against the following bacteria:

Gram-positive aerobic bacteria.

Staphylococcus aureus, Streptococcus pyogenes (group A beta-haemolytic streptococci), Streptococcus pneumoniae, alpha-haemolytic streptococci (viridans group) and other Streptococci.

Gram-negative aerobic bacteria.

Haemophilus influenzae (including beta-lactamase producing Haemophilus influenzae), Haemophilus parainfluenzae, Moraxella catarrhalis.

Other organisms.

Chlamydia trachomatis, Chlamydia pneumoniae, Mycoplasma pneumoniae.

Opportunistic pathogens associated with HIV infections.

MAC.
In Australia, macrolide resistance for Streptococcus pneumoniae and Staphylococcus aureus has been increasing since the late 1990's. Resistance rates of 15% or more are regularly reported. The use of macrolides should be guide by culture susceptibility results and practice guidelines.
Susceptibility testing.

Dilution or diffusion techniques.

Either quantitative (minimal inhibitory concentration [MIC]) or breakpoint, should be used following a regularly updated, recognised and standardised method (e.g. NCCLS). Standardised susceptibility test procedures require the use of laboratory control microorganisms to control the technical aspects of the laboratory procedures.
A report of "Susceptible" indicates that the pathogen is likely to be inhibited when the patient is given the recommended dose. A report of "Intermediate" indicates that the result should be considered equivocal, and if the microorganism is not fully susceptible to alternative, clinically feasible drugs, the test should be repeated. This category implies possible clinical applicability in body site where the drug is physiologically concentrated or in situations where high dosage of drug can be used. This category also provides a buffer zone, which prevents small uncontrolled technical factors from causing major discrepancies in interpretation.
A report of "Resistant" indicates that the pathogen is not likely to be inhibited when the patient is given the recommended dose; other therapy should be selected.

Susceptibility testing for Mycobacterium avium complex (MAC).

The disk diffusion techniques and dilution methods for susceptibility testing against gram-positive and gram-negative bacteria should not be used for determining azithromycin MIC values against mycobacteria. In vitro susceptibility testing methods and diagnostic products currently available for determining minimal inhibitory concentration (MIC) values against MAC organisms have not been established or validated. Azithromycin MIC values will vary depending on the susceptibility testing method employed, composition and pH of media and the utilization of nutritional supplements. Breakpoints to determine whether clinical isolates of M. avium or M. intracellulare are susceptible to azithromycin have not been established.

Clinical trials.

Disseminated MAC disease prophylaxis. In a placebo-controlled study patients receiving azithromycin were less than one-half as likely to develop MAC bacteraemia as those on placebo. The one-year cumulative incidence rate of disseminated MAC disease was 8.24% on azithromycin and 20.22% on placebo.
In a comparative study the risk of developing MAC bacteraemia in patients receiving azithromycin was less than that observed for patients receiving rifabutin. Patients on a combination of azithromycin and rifabutin were approximately one-third as likely to develop MAC bacteraemia as those patients receiving either agent alone. The one-year cumulative incidence rate of disseminated MAC disease was 7.62% on azithromycin, 15.25% on rifabutin and 2.75% on azithromycin and rifabutin. However, patients receiving the combination were more likely to discontinue therapy due to poor tolerability.
Trachoma.

Trachoma - children and adults.

Information from clinical trial data and published reports of studies supports the efficacy of 20 mg/kg to 1 g, taken either as a single dose or each week for three weeks, in the treatment of trachoma in children and adults. The single dose schedule has not been compared with the three weekly dosing schedule in clinical trials.

Trachoma - repeat courses.

While the statistically significant superiority of a single dose of azithromycin given as a single dose and repeated at 6 months versus a single dose of azithromycin to adults or children with active trachoma has not been determined, information from clinical trial data suggests that the trachoma free period may be extended by a repeat single dose of azithromycin at 6 months.
Pharyngitis/tonsillitis. In a clinical trial (study 96-001), 501 children aged 2 - 12 years with a clinical diagnosis of acute tonsillitis received azithromycin 10 mg/kg/day or 20 mg/kg/day for 3 days or penicillin V, 50 mg/kg (in 3 divided doses) for 10 days. (Note the recommended dose for penicillin V in Australia is 20 mg/kg/day). Similar clinical efficacy but greater bacteriological eradication was evident at the 20 mg/kg/day dose (the daily dose did not exceed 500 mg). Group A beta-haemolytic streptococci (GABHS) eradication rates and clinical response rates are detailed in Tables 3 and 4.

5.2 Pharmacokinetic Properties

Absorption.

Following oral administration of a 500 mg dose, azithromycin is absorbed from the gastrointestinal tract with an absolute bioavailability of 37%. Maximum serum concentration (Cmax) of 0.3 - 0.4 microgram/mL is achieved in 2-3 hours with an area under the curve AUC(0-24) of 2.6 microgram hr/mL.
Food has no significant effect on the bioavailability of the Zithro tablets, even after a high fat meal.
Pharmacokinetics in elderly subjects are substantially the same and no dosage adjustment is necessary. The extent of absorption is unaffected by co-administration with antacid; however, Cmax is reduced by up to 30%. Administration of an 800 mg dose of cimetidine two hours prior to azithromycin had no effect on azithromycin absorption. Azithromycin did not affect the plasma levels or pharmacokinetics of carbamazepine, methylprednisolone, zidovudine or multiple oral doses of theophylline (see Section 4.5 Interactions with Other Medicines and Other Forms of Interactions).

Distribution.

Serum concentrations decline in a polyphasic pattern, resulting in an average terminal half-life of 68 hours. The high values for apparent steady-state volume of distribution (31.1 L/kg) and plasma clearance (630 mL/min) suggest that the prolonged half-life is due to extensive uptake and subsequent release of drug from tissues. Azithromycin concentrations in the cerebro-spinal fluid are very low. Concentrations in the peritoneal fluid are also very low.
Azithromycin is distributed widely throughout the body. Rapid movement of azithromycin from blood into tissues results in significantly higher azithromycin concentrations in tissues than in plasma (from 1-60 times the maximum observed concentration in plasma). It appears to be concentrated intracellularly. Concentrations in tissues, such as lung, tonsil and prostate, etc. exceed the MIC90 for likely pathogens after a single dose of 500 mg, and remain high after serum or plasma concentrations decline to below detectable levels. Mean peak concentrations observed in peripheral leucocytes, the site of MAC infection, were 140 microgram/mL and remained above 32 microgram/mL for approximately 60 hours following a single 1200 mg oral dose. The serum protein binding of azithromycin is variable in the concentration range approximating human exposure, decreasing from 51% at 0.02 microgram/mL to 7% at 2 microgram/mL.

Metabolism.

Very high concentrations of unchanged drug have been found, together with 10 metabolites, formed by N- and O-demethylation, by hydroxylation of the desosamine and aglycone rings, and by cleavage of the cladinose conjugate. Comparison of HPLC and microbiological assays in tissues suggests that metabolites play no part in the microbiological activity of azithromycin.

Excretion.

Approximately 12% of an intravenously administered dose is excreted in the urine over 3 days as the parent drug, the majority in the first 24 hours. Biliary excretion of azithromycin is a major route of elimination for unchanged drug following oral administration.
Following a single oral dose of azithromycin 1 gram, the pharmacokinetics in subjects with GFR 10 - 80 mL/min were not affected. Statistically significant differences in AUC0-120 (8.8 microgram.hr/mL vs. 11.7 microgram.hr/mL), Cmax (1.0 microgram/mL vs. 1.6 microgram/mL) and CLr (2.3 mL/min/kg vs. 0.2 mL/min/kg) were observed between subjects with GFR < 10 mL/min and subjects with GFR > 80 mL/min.
In patients with mild (Class A) to moderate (Class B) hepatic impairment, there is no evidence of a marked change in serum pharmacokinetics of azithromycin compared to those with normal hepatic function. In these patients, urinary recovery of azithromycin appears to increase, perhaps to compensate for reduced hepatic clearance.
Azithromycin did not affect the prothrombin time response to a single dose of warfarin. However, prudent medical practice dictates careful monitoring of prothrombin time in all patients.

Powder for oral suspension#.

Bioavailability studies in the fed and fasted state have been conducted with azithromycin. Administration of azithromycin immediately following a high fat meal resulted in a slight increase in the rate of absorption but no change in the fraction of the dose absorbed. This effect is probably of no clinical significance. A separate bioavailability study has confirmed bioequivalence between the powder for suspension and sachet.
# Azithromycin powder for oral suspension is unavailable in Zithro brand however is available in other brands.
Azithromycin has similar pharmacokinetic characteristics in adults and children. There is a linear relationship between AUC and Cmax and dose, for doses between 10 and 20 mg/kg daily in children.

5.3 Preclinical Safety Data

Genotoxicity.

Azithromycin showed no genotoxic potential in a range of standard laboratory tests for gene mutations and chromosomal damage.

Carcinogenicity.

No studies have been done to determine the carcinogenic potential of azithromycin in animals.

6 Pharmaceutical Particulars

6.1 List of Excipients

Zithro tablets contain the following inactive ingredients: pregelatinised maize starch, crospovidone, calcium hydrogen phosphate, sodium lauryl sulfate, and magnesium stearate. The coating of the tablets contains lactose monohydrate, hypromellose, titanium dioxide and triacetin.
See Section 2 Qualitative and Quantitative Composition.

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 25°C.

6.5 Nature and Contents of Container

Zithro tablets 500 mg are packaged in blister packs of 2 and 3 and 15* tablets.
Azithromycin 500 mg film-coated tablets are packed in blisters, transparent PVC film sealed with aluminium foil.
* Not currently marketed in Australia.

6.6 Special Precautions for Disposal

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

6.7 Physicochemical Properties

Azithromycin is the first of a new class of antibiotics designated chemically as azalides, a subclass of macrolides, available for oral administration. Azithromycin, chemically 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A, contains a methyl substituted nitrogen atom at position 9A of the lactone ring.
Azithromycin dihydrate is a white crystalline powder with a chemical formula of C38H72N2O12.2H2O and a molecular weight of 785.0.
Azithromycin dihydrate is practically insoluble in water, freely soluble in ethanol and in methylene chloride.

Chemical structure.


CAS number.

CAS: 83905-01-5.

7 Medicine Schedule (Poisons Standard)

S4 (Prescription Medicine).

Summary Table of Changes