Consumer medicine information

Formet Tablets

Metformin hydrochloride

BRAND INFORMATION

Brand name

Formet 500

Active ingredient

Metformin hydrochloride

Schedule

S4

 

Consumer medicine information (CMI) leaflet

Please read this leaflet carefully before you start using Formet Tablets.

What is in this leaflet

This leaflet answers some common questions about FORMET.

It does not contain all the available information. It does not take the place of talking to your doctor, pharmacist or diabetes educator.

All medicines have risks and benefits. Your doctor has weighed the risk of you taking FORMET against the benefits it is expected to have for you.

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

Keep this leaflet with the medicine. You may want to read it again.

What FORMET is used for

The name of your medicine is FORMET. It contains the active ingredient metformin hydrochloride.

Metformin is used to control blood glucose (the amount of sugar in the blood) in patients with diabetes mellitus, when diet and exercise are not enough to control blood glucose.

Metformin can be used in patients with Type II diabetes mellitus in adults and children over 10 years of age. It is especially useful in those who are overweight, when diet and exercise are not enough to lower blood glucose levels (hyperglycaemia). For adult patients, metformin can be used alone, or in combination with other oral diabetic medicines or in combination with insulin in insulin requiring Type II diabetes.

Ask your doctor if you have any questions about why FORMET was prescribed for you. Your doctor may have prescribed FORMET tablets for another reason.

FORMET is only available with a doctors prescription.

There is no evidence that FORMET is addictive.

How FORMET works

Metformin belongs to a group of medicines called biguanides. Metformin lowers high blood glucose (hyperglycaemia) by helping your body make better use of the insulin produced by your pancreas.

If your blood glucose is not properly controlled, you may experience hypoglycaemia (low blood glucose) or hyperglycaemia (high blood glucose). High blood glucose can lead to serious problems with your heart, eyes, circulation or kidneys.

Low blood glucose can occur suddenly.

Signs may include:

  • weakness, trembling or shaking
  • sweating
  • lightheadedness, dizziness, headache or lack of concentration
  • tearfulness or crying
  • irritability
  • hunger
  • numbness around the lips and tongue.

If not treated promptly, these may progress to:

  • loss of co-ordination
  • slurred speech
  • confusion
  • loss of consciousness or fitting.

High blood glucose usually occurs more slowly than low blood glucose. Signs of high blood glucose may include:

  • lethargy or tiredness
  • headache
  • thirst
  • passing large amounts of urine
  • blurred vision.

Before you take FORMET

When you must not take it

Do not take metformin if you have had an allergic reaction to medicines containing metformin or any of the ingredients listed at the end of this leaflet.

Symptoms of an allergic reaction may include:

  • shortness of breath, wheezing or difficulty breathing
  • swelling of the face, lips, tongue or other parts of the body
  • rash, itching or hives on the skin.

If you are not sure if you have an allergy to metformin check with your doctor.

Do not take metformin if you have any of the following medical conditions:

  • Type I diabetes mellitus that is well controlled by insulin alone
  • Type II diabetes that is already well controlled by diet alone
  • Any type of metabolic acidosis such as lactic acidosis, diabetis ketoacidosis (a symptom of uncontrolled diabetes, in which substances called ketone bodies build up in the blood – you may notice this as an unusual fruity odour on your breath, difficulty breathing, confusion and frequent urination)
  • severe liver disease
  • excessive alcohol intake, binge drinking, alcohol dependence
  • kidney failure or disease
  • dehydration, severe blood loss, shock
  • severe infection
  • certain heart or blood vessel problems, including a recent heart attack or severe heart failure (when the heart fails to pump blood effectively)
  • severe breathing difficulties
  • blood clots in the lungs (symptoms include coughing, shortness of breath, chest pain, and a fast heart rate)
  • gangrene
  • inflammation of the pancreas (pancreatitis), symptoms include severe upper stomach pain, often with nausea and vomiting.

Do not take FORMET if you need to have major surgery or an examination such as an X-ray or a scan requiring an injection of iodinated contrast (dye). You must stop taking FORMET for a certain period of time before and after the examination or surgery. Your doctor will decide whether you need any other treatment for this time. It is important that you follow your doctor’s instructions precisely.

Do not take FORMET if you are pregnant or intend becoming pregnant. The safety of FORMET in pregnant women has not been established.

Insulin is more suitable for controlling blood glucose during pregnancy. Your doctor will replace FORMET with insulin while you are pregnant.

Do not take FORMET if you are breastfeeding. FORMET is not recommended while you are breasfeeding. Your doctor will discuss the options available to you.

Do not take FORMET after the expiry date (EXP) printed on the pack. If you take this medicine after the expiry date has passed, it may not work as well.

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

If you are not sure whether you should start taking FORMET, talk to your doctor or pharmacist.

Before you start to take it

Tell your doctor if you have allergies to:

  • any other medicines
  • any other substances, such as foods, preservatives or dyes.

Tell your doctor if you are breastfeeding or plan to breastfeed. It is not known whether metformin passes into breast milk.

Metformin is usually not recommended while you are breastfeeding. Your doctor will discuss the risks and benefits of taking metformin when breastfeeding.

Tell your doctor if you have or have had any medical conditions, especially the following:

  • kidney disease
  • heart failure
  • high blood pressure
  • recent heart attacks
  • liver disease
  • clots in the lung.

Tell your doctor if:

  • you ever drink alcohol
  • you do not eat regular meals
  • you do heavy exercise or work
  • you are ill or feeling unwell.

Alcohol, diet, exercise and your general health all strongly affect the control of your diabetes. Alcohol can affect the control of your diabetes. Drinking excessive amounts of alcohol while you are being treated with FORMET may also lead to serious side effects. Your doctor may suggest you stop drinking or reduce the amount of alcohol you drink. Discuss these things with your doctor.

If you have not told your doctor, pharmacist or diabetes educator about any of the above, tell them before you start taking metformin.

Taking other medicines

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

Some medicines may hide the symptoms of low blood sugar (hypoglycaemia). These include:

  • alcohol
  • certain medicines used to treat high blood pressure e.g. betablockers.

Some medicines and FORMET may interact with each other. These include:

  • other medicines to treat diabetes
  • alcohol, including medicines such as cough and cold syrups which may contain alcohol
  • tetracosactrin, a medicine used in people with multiple sclerosis, and in young children to treat some types of seizures (fits)
  • danazol, a medicine used to treat endometriosis
  • some medicines used to treat high blood pressure and some heart conditions, including beta-blockers, calcium channel blockers and ACE inhibitors
  • medicines used to prevent blood clots, such as warfarin
  • diuretics, also known as fluid tablets e.g. thiazides, frusemide
  • chlorpromazine, a medicine used to treat schizophrenia and other mental illnesses
  • NSAIDs (non-steroidal anti-inflammatory drugs), medicines used to relieve pain, swelling and other symptoms of inflammation, such as aspirin, diclofenac, ibuprofen, meloxicam, naproxen or piroxicam
  • cimetidine, a medicine used to treat reflux and ulcers
  • corticosteroids such as prednisolone and cortisone
  • some medicines used to treat asthma such as salbutamol or terbutaline
  • medicines that are substrate/ inhibitors of organic cation transporters – OCT 1 such as veraprimil; OCT 2 such as dolutegravir, crizotinib, olaparib, daclatasvir or vandetanib
  • medicines that are inducers of OTC 1 such as rafampicin
  • medicines that may increase the risk of lactic acidosis when concomitantly used with metformin hydrochloride such as topiramate and other carbonic anhydrase inhibitors.

You may need different amounts of your medicine or you may need to take different medicines. Your doctor, pharmacist or diabetes educator can tell you what to do if you are taking any of these medicines. They also have a more complete list of medicines to be careful with or avoid while taking metformin.

Ask your doctor or pharmacist if you are not sure if you are taking any of these medicines.

How to take FORMET

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

If you do not understand the instructions on the box, ask your doctor or pharmacist for help. Your doctor will tell you how much to take and when to take it.

Take FORMET exactly as directed by your doctor.

How much to take

The dose varies from patient to patient. Your doctor will decide the right dose for you.

The usual dose of metformin for adults is 500 mg one to three times a day, up to a maximum of 1 g three times a day.

Your doctor may increase or decrease the dose, depending on your blood glucose levels.

FORMET can be taken by children with diabetes that cannot be controlled with insulin and who are being treated in hospital. Your child's doctor will decide the dose.

How to take it

Swallow the tablets with a glass of water.

When to take it

Take FORMET during or immediately after a meal, at about the same time each day. This will reduce the chance of a stomach upset.

Do not skip meals while taking metformin.

How long to take it

Continue taking FORMET for as long as your doctor recommends.

Make sure you keep enough FORMET to last over weekends and holidays.

FORMET will help control your diabetes but will not cure it. Therefore, you may have to take it for a long time.

If you forget to take it

If it is almost time for your next dose, skip the dose you missed and take your next dose when you are meant to.

Otherwise, take it as soon as you remember (with food), and then go back to taking your medicine as you would normally.

Do not take a double dose to make up for the dose that you missed. If you double a dose, this may cause low blood sugar (hypoglycaemia).

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

If you take too much (overdose)

Immediately telephone your doctor or the Poisons Information Centre (telephone 13 11 26), or go to Accident & Emergency at your nearest hospital, if you think that you or anyone else may have taken too much FORMET.

Do this even if there are no signs of discomfort or poisoning.

If you take too much metformin together with other medicines for diabetes or alcohol, you may experience symptoms of low blood sugar (hypoglycaemia).

At the first signs of hypoglycaemia, raise your blood glucose quickly by eating jelly beans, sugar or honey, drinking non-diet soft drink or taking glucose tablets.

If not treated quickly, these symptoms may progress to loss of co-ordination, slurred speech, confusion, fits or loss of consciousness.

If you take too much metformin, you may feel sick, vomit, have trouble breathing and have stomach pain or diarrhoea. These may be the early signs of a serious condition called lactic acidosis.

If you experience any of these symptoms, immediately get medical help.

While you are using FORMET

Things you must do

Tell your doctor if:

  • you become pregnant while you are taking metformin,
  • you are about to start taking any new medicines
  • you do not eat regular meals
  • you do heavy exercise or work
  • you are feeling unwell.

Diet and exercise and your general health all strongly affect the control of your diabetes. Discuss these with your doctor. If you have not told your doctor, pharmacist or diabetes educator about any of the above, tell them before you start FORMET.

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

Make sure that you, your friends, family and work colleagues can recognise the symptoms of low blood sugar and high blood sugar and know how to treat them.

HYPOGLYCAEMIA

FORMET does not normally cause hypoglycaemia, although you may experience it if you take other medicines for diabetes such as sulfonylureas or repaglinide; or if you also use insulin.

Hypoglycaemia can occur suddenly. Initial signs may include:

  • weakness, trembling or shaking
  • sweating
  • lightheadedness, dizziness, headache or lack of concentration
  • irritability, tearfulness or crying
  • hunger
  • numbness around the lips and tongue

If not treated promptly, these may progress to:

  • loss of co-ordintation
  • slurred speech
  • confusion
  • fits or loss of consciousness

If you experience any of the symptoms of low blood sugar, you need to raise your blood glucose immediately.

You can do this by doing one of the following:

  • eating 5 to 7 jelly beans
  • eating 3 teaspoons of sugar or honey
  • drinking half a can of ordinary (non-diet) soft drink
  • taking 2 to 3 concentrated glucose tablets.

Unless you are within 10 to 15 minutes of your next meal or snack, follow up with extra carbohydrates such as plain biscuits, fruit or milk. Taking this extra carbohydrate will prevent a second drop in your blood glucose level.

HYPERGLYCAEMIA

If you experience any of the signs of high blood sugar (hyperglycaemia), contact your doctor immediately.

The risk of high blood sugar is increased in the following situations:

  • undiagnosed or uncontrolled diabetes
  • illness, infection or stress
  • taking too little metformin
  • taking certain other medicines
  • too little exercise
  • eating more carbohydrates than normal.

If you are about to be started on any new medicine, remind your doctor and pharmacist that you are taking FORMET.

Tell all the other doctors, dentists and pharmacists who treat you that you are taking this medicine.

If you become pregnant while taking FORMET, tell your doctor immediately.

Tell your doctor if any of the following happen:

  • you become ill
  • you become dehydrated (for instance due to persistent or severe diarrhoea or recurrent vomiting
  • you are injured
  • you have a fever
  • you have a serious infection such as influenza, respiratory tract infection or urinary tract infection
  • you are having major surgery
  • you are having an examination such as an X-ray or a scan requiring an injection of an iodinated contrast agent (dye)

Your blood glucose may become difficult to control at these times. You may also be more at risk of developing a serious condition called lactic acidosis. At these times, your doctor may replace FORMET with insulin.

Visit your doctor regularly for check-ups. Your doctor may want to perform blood tests to check your kidneys, liver, heart and vitamin B12 level while you are taking FORMET.

Check your blood glucose levels regularly. This is the best way to tell if your diabetes is being controlled properly. Your doctor or diabetes educator will show you how and when to do this.

When you start treatment with FORMET, it can take up to two weeks for your blood glucose levels to be properly controlled.

Carefully follow the advice of your doctor and dietician on diet, drinking alcohol and exercise.

Things you must not do

Do not give metformin to anyone else, even if they have the same condition as you.

Do not skip meals while taking metformin.

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

Do not give FORMET to anyone unconscious or with a diabetic coma.

Things to be careful of

If you have to be alert, for example when driving, be especially careful not to let your blood glucose levels fall too low. Low blood glucose levels may slow your reaction time and affect your ability to drive or operate machinery. Drinking alcohol can make this worse. However, metformin by itself is unlikely to affect how you drive or operate machinery.

If you are sick with a cold, fever or flu, it is very important to continue eating your normal meals. Your diabetes educator or dietician can give you a list of foods to eat on a sick day.

If you are travelling, it is a good idea to:

  • wear some form of identification showing you have diabetes
  • carry some form of sugar to treat hypoglycaemia if it occurs, for example, sugar sachets or jelly beans
  • carry emergency food rations in case of a delay, for example, dried fruit, biscuits or muesli bars
  • keep FORMET readily available.

Lifestyle measures that help reduce heart disease risk

By following these simple measures, you can further reduce the risk from heart disease.

  • Quit smoking and avoid secondhand smoke
  • Limit alcohol intake
  • Enjoy healthy eating by:
    - eating plenty of vegetables and fruit;
    - reducing your saturated fat intake (eat less fatty meats, full fat dairy products, butter, coconut and palm oils, most take-away foods, commercially-baked products)
  • Be active. Progress, over time, to at least 30 minutes of moderate intensity physical activity on 5 or more days each week. Can be accumulated in shorter bouts of 10 minutes duration. If you have been prescribed anti-angina medicine, carry it with you when being physically active
  • Maintain a healthy weight
  • Discuss your lifestyle and lifestyle plans with your doctor
  • For more information and tools to improve your heart health, call Heartline, the Heart Foundation's national telephone information service, on 1300 36 27 87 (local call cost)

Know warning signs of heart attack and what to do:

  • Tightness, fullness, pressure, squeezing, heaviness or pain in your chest, neck, jaw, throat, shoulders, arms or back
  • You may also have difficulty breathing, or have a cold sweat or feel dizzy or light headed or feel like vomiting (or actually vomit).

If you have heart attack warning signs that are severe, get worse or last for 10 minutes even if they are mild, call triple zero (000). Every minute counts.

Side effects

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

FORMET helps most people with diabetes, 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.

If you are over 65 years of age you may have an increased chance of getting side effects.

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

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

  • stomach upset such as feeling sick (nausea)
  • vominting
  • diarrhoea
  • stomach pain
  • taste disturbance
  • loss of appetite
  • skin reactions such as redness of the skin, itching or itchy rash (urticaria).

These are generally mild side effects which usually occur during the first few weeks. Taking FORMET with meals can help reduce nausea and diarrhoea. Skin rash is rare; it is usually not serious and should go away in a few days.

Tell your doctor immediately or go to the accident and emergency department at your nearest hospital if you notice any of the following symptoms of lactic acidosis (high lactic acid in the blood):

  • vomiting, stomach pain
  • trouble breathing
  • feeling weak, tired, or generally unwell
  • unusual muscle pain
  • sleepiness
  • dizziness or lightheadedness
  • shivering, feeling extremely cold
  • slow heart beat.

Lactic acidosis is a very rare but serious side effect requiring urgent medical attention or hospitalisation. Although rare, if lactic acidosis does occur, it can be fatal. The risk of lactic acidosis is higher in the elderly, those whose diabetes is poorly controlled, those with prolonged fasting, those with certain heart conditions, those who drink alcohol and those with kidney or liver problems.

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

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

Some side effects (e.g. reduced vitamin B12 level) can only be found when your doctor does tests from time to time to check your progress.

After using FORMET

Storage

Keep your tablets in the pack until it is time to take them. If you take the tablets out of the pack they will not keep well.

Keep your tablets in a cool dry place where the temperature stays below 30°C. Do not store metformin or any other medicine in the bathroom or near a sink.

Do not leave it in the car on hot days or on window sills. Heat and dampness can destroy some medicines.

Keep it where 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

If your doctor tells you to stop using the tablets, or the tablets have passed their expiry date, ask your pharmacist what to do with any that are left over.

Product description

What FORMET looks like

  • 500 mg tablet – oblong, white tablet, marked with M|O on one side and ‘>’ on the other
    FORMET 500 mg tablets are available in bottles and blister packs containing 100 tablets
  • 850 mg tablet – round, white tablet, marked with MO on one side and ‘>’ on the other
    FORMET 850 mg tablets are available in blister packs containsing 60 tablets
  • 1000 mg tablet - oval, white tablet, marked M|O on one side on the other.
    FORMET 1000 mg tablets are available in bottles and blister packs containing 90 tablets.

Ingredients

The active ingredient in FORMET is metformin hydrochloride:

  • each 500 mg tablet contains 500 mg of metformin hydrochloride
  • each 850 mg tablet contains 850 mg of metformin hydrochloride
  • each 1000 mg tablet contains 1000 mg of metformin hydrochloride.

The tablets also contain:

  • povidone
  • magnesium stearate
  • purifed water
  • Opadry Clear OY-29020

The tablets do not contain lactose, gluten, sucrose, tartrazine or any other azo dyes.

Sponsor

Arrow Pharma Pty Ltd
15-17 Chapel Street
Cremorne VIC 3121

Australian registration numbers:

FORMET 500 mg tablet bottle – AUST R 91107

FORMET 500 mg tablet blister – AUST R 91108

FORMET 850 mg tablet blister – AUST R 91111

FORMET 1000 mg tablet bottle – AUST R 91112

FORMET 1000 mg tablet blister – AUST R 91113

This leaflet was prepared in November 2019.

Published by MIMS January 2020

BRAND INFORMATION

Brand name

Formet 500

Active ingredient

Metformin hydrochloride

Schedule

S4

 

1 Name of Medicine

Metformin hydrochloride.

2 Qualitative and Quantitative Composition

Formet tablets come in four strengths:
Formet 250 contains 250 mg metformin hydrochloride.
Formet 500 contains 500 mg metformin hydrochloride.
Formet 850 contains 850 mg metformin hydrochloride.
Formet 1000 contains 1000 mg metformin hydrochloride.
The tablets are gluten free.
For the full list of excipients, see Section 6.1 List of Excipients.

3 Pharmaceutical Form

Film-coated tablets.

Formet 250.

Round, white tablet (approx. 9 mm), embossed with MO on one side and the Arrow symbol, ">" on the other.

Formet 500.

Oblong, white film-coated tablet, embossed with M/O on one side and the Arrow symbol, ">" on the other.

Formet 850.

Round, white film-coated tablet (approx. 13 mm), embossed with MO on one side and the Arrow symbol, ">" on the other.

Formet 1000.

Oval, white tablet, embossed with M/O on one side and ">/>" on the other.

4 Clinical Particulars

4.1 Therapeutic Indications

Metformin is indicated in the treatment of type 2 diabetes mellitus not satisfactorily controlled by diet, where the risk of lactic acidosis is minimised by excluding predisposing factors, especially impaired renal, hepatic or cardiovascular function.
Metformin may be used as initial therapy or in sulphonylurea failure, either alone or in combination with a sulphonylurea or as adjuvant therapy in insulin dependent diabetes.

4.2 Dose and Method of Administration

Life threatening lactic acidosis can occur due to accumulation of metformin. Risk factors include renal impairment, old age and high doses of metformin above 2 g per day.
It is important that the tablets are taken in divided doses with meals.
Initially 500 mg should be taken once or twice a day and, if necessary, increased over a few weeks up to 1 g three times per day. The dose should be titrated with gradual dose increments until the desired effect is obtained. 500 mg three times a day is often sufficient to obtain diabetic control. If necessary, the dose can be increased to 1 g three times daily, which is the maximum recommended daily dose. Control may be attained within a few days but occasionally requires up to two weeks. Once control has been obtained, the dosage should be reviewed and reduced to the lowest maintenance level consistent with good diabetic control.
The 250 mg tablet should be used only for the purpose of dose titration. There are no clinical data to support a minimum effective dose lower than 500 mg. If dose titration has been achieved with one tablet strength, then the patient's response should be reassessed if a different strength or dose schedule is commenced.
Metformin dosage should be frequently reviewed in patients stabilised on metformin, especially if they develop an illness, as they may tolerate the drug less well, particularly if the illness is accompanied by a decrease in renal function. If necessary, metformin should be ceased for a few days during an illness and then restarted at low dosage, as for initial therapy.
The action of Formet is progressive and no final assessment of the patient's real response should be made before the 21st day of treatment; blood sugar estimations are recommended during the initial 15 days of stabilisation. Metformin will not produce a hypoglycaemic state when used alone; however, due to its action in increasing insulin effectiveness, care must be taken when Formet is initially administered with parenteral doses of insulin.

Elderly.

The initial and maintenance dosing of metformin should be conservative in elderly patients, due to the potential for decreased renal function in this population. Any dosage adjustment should be based on a careful assessment of renal function. Generally, elderly patients should not be titrated to the maximum dose of metformin.
In debilitated or malnourished patients, the dosing should be conservative and based on a careful assessment of renal function.

4.3 Contraindications

Juvenile diabetes mellitus that is uncomplicated and well regulated on insulin.
Diabetes mellitus regulated by diet alone.
During or immediately following surgery where insulin is essential.
Hypersensitivity to metformin hydrochloride or to any of the excipients.
Any type of metabolic acidosis (such as lactic acidosis, diabetic ketoacidosis).
Diabetic pre-coma.
Renal failure or renal dysfunction (creatinine clearance < 60 mL/minute).
Acute conditions with the potential to alter renal function such as: dehydration; severe infection; shock; intravascular administration of iodinated contrast material (see Section 4.4 Special Warnings and Precautions for Use).
Acute or chronic disease which may cause tissue hypoxia such as: cardiac failure; recent myocardial infarction; respiratory failure; pulmonary embolism; shock; acute significant blood loss; sepsis; gangrene; pancreatitis.
Elective major surgery (see Section 4.4 Special Warnings and Precautions for Use).
Severe hepatic insufficiency: acute alcohol intoxication; alcoholism.
Lactation.

4.4 Special Warnings and Precautions for Use

Lactic acidosis.

Lactic acidosis is a rare but serious (high mortality in the absence of prompt treatment), metabolic complication which can occur due to metformin accumulation during treatment with Formet. When it occurs, it is fatal in approximately 50% of cases. Lactic acidosis is a medical emergency and must be treated in hospital immediately. The risk of lactic acidosis increases with the degree of renal dysfunction and the patient's age. Reported cases have occurred primarily in diabetic patients with significant renal failure, often in the setting of multiple concomitant medical/surgical problems and multiple concomitant medications. The incidence of lactic acidosis can and should be reduced by assessing other risk factors such as poorly controlled diabetes, ketosis, prolonged fasting, excessive alcohol intake, hepatic insufficiency and any condition associated with hypoxia.
The reported incidence of lactic acidosis in patients receiving metformin is very low (approximately 0.03 cases per 1,000 patient years, with approximately 0.015 fatal cases per 1,000 patient years). The onset is often subtle and accompanied by nonspecific symptoms such as malaise, myalgia, respiratory distress, increasing somnolence and nonspecific abdominal distress. Lactic acidosis may also occur in association with a number of pathophysiological conditions, including diabetes mellitus, and when there is significant tissue hypoperfusion and hypoxaemia. Lactic acidosis is characterised by acidosis (decreased blood pH), elevated lactate levels with increased lactate/pyruvate ratio and electrolyte disturbances with an increased anion gap.

Diagnosis.

The risk of lactic acidosis must be considered in the event of non-specific signs such as muscle cramps with digestive disorders such as abdominal pain and severe asthenia.
Lactic acidosis is characterised by acidotic dyspnea, abdominal pain and hypothermia followed by coma. Diagnostic laboratory findings are decreased blood pH, plasma lactate levels above 5 mmol/L, and an increased anion gap and lactate/pyruvate ratio. If metabolic acidosis is suspected, metformin should be discontinued and the patient should be hospitalised immediately (see Section 4.9 Overdose, Treatment).

Administration of iodinated contrast material.

The intravascular administration of iodinated contrast materials in radiologic studies can lead to renal failure. This may induce metformin accumulation and may expose to lactic acidosis. Therefore, metformin must be discontinued either 48 hours before the test when renal function is known to be impaired or from the time of the test when renal function is known to be normal. Metformin may not be reinstituted until 48 hours afterwards, and only after renal function has been re-evaluated and found to be normal (see Section 4.5 Interactions with Other Medicines and Other Forms of Interactions).

Surgery.

Metformin hydrochloride must be discontinued 48 hours before elective major surgery. Therapy may be restarted no earlier than 48 hours following surgery and only after renal function has been reevaluated and found to be normal.

Heart failure.

Type 2 diabetic patients with heart failure are at an increased risk of hypoperfusion and possible renal insufficiency. Renal insufficiency is a risk factor for systemic accumulation of metformin and consequently lactic acidosis. Careful monitoring of renal function is recommended when metformin is used in patients with cardiac failure. When metformin is implicated as the cause of lactic acidosis, metformin plasma levels greater than 5 microgram/mL are generally found (see Section 5.2 Pharmacokinetic Properties). Underlying renal disease, or a deterioration in renal function, result in reduced clearance of metformin and drug accumulation and are therefore major risk factors in lactic acidosis. The risk of lactic acidosis may therefore be significantly decreased by regular monitoring of renal function in patients taking metformin and by the use of the minimum effective dose of metformin. In addition, metformin therapy should be temporarily stopped in the presence of any condition associated with hypoxaemia or dehydration, in patients suffering from serious infections or trauma (particularly if gastrointestinal disturbances are noted or acidosis is suspected) and in those undergoing surgery.

Use in hepatic impairment.

Periodic assessment of hepatic and cardiovascular function is recommended during prolonged periods of treatment with metformin.

Use in renal impairment.

As metformin hydrochloride is excreted by the kidney, it is recommended that creatinine clearance and/or serum creatinine levels be determined before initiating treatment and regularly thereafter:
At least annually in patients with normal renal function;
At least two to four times a year in patients with serum creatinine levels at the upper limit of normal and in elderly subjects.
Decreased renal function in elderly subjects is frequent and asymptomatic. Special caution should be exercised in situations where renal function may become impaired, for example when initiating antihypertensive therapy or diuretic therapy and when starting therapy with a non-steroidal antiinflammatory drug (NSAID).

Use in the elderly.

The risk of lactic acidosis, in association with metformin, is increased in elderly patients on long term therapy. due to the physiological alteration of the renal function and the possible accumulation of metformin. Metformin may be used in the elderly if contraindications and precautions are respected, the dosage is frequently reviewed and renal function monitored.
Decreased renal function in elderly subjects is frequent and asymptomatic. Special caution should be exercised in situations where renal function may become impaired.

Paediatric use.

Formet is not recommended for use in children, except those with insulin resistant diabetes who are being treated in hospital.
The diagnosis of type 2 diabetes mellitus should be confirmed before treatment with metformin is initiated.
No effect of metformin on growth and puberty has been detected during controlled clinical studies of one-year duration but clinical data in relation to the long-term effect of metformin on the development of skeletal and reproductive system in children and adolescents are not available. Therefore, a careful follow-up of the effect of metformin on these parameters in metformin-treated children, especially pre-pubescent children, is recommended.

Effects on laboratory tests.

No information is available.

Other precautions.

All patients should continue their diet with a regular distribution of carbohydrate intake during the day. Overweight patients should continue their energy-restricted diet.
The usual laboratory tests for diabetes monitoring should be performed regularly.
Metformin hydrochloride alone does not cause hypoglycaemia; however, caution is advised when it is used in combination with other antidiabetic agents (sulphonylureas, glinides, insulin).

Patients receiving continuous metformin therapy.

It is recommended that serum vitamin B12 levels be measured prior to initiation treatment with metformin, after 6 months treatment and thereafter annually because of reports of decreased vitamin B12 absorption associated with metformin administration.
Alcohol is known to potentiate the effect of metformin on lactate metabolism. Patients should therefore be warned against excessive alcohol intake, acute or chronic, while taking metformin.

4.5 Interactions with Other Medicines and Other Forms of Interactions

Pharmacokinetic interactions.

Cimetidine.

Reduced clearance of metformin has been reported during cimetidine therapy, so a dose reduction should be considered.

Anticoagulants.

Metformin increases the elimination rate of vitamin K antagonists. Consequently, the prothrombin time should be closely monitored in patients in whom metformin and vitamin K antagonists are being coadministered. Cessation of metformin in patients receiving vitamin K antagonists can cause marked increases in the prothrombin time.

Nifedipine.

A single dose, metformin/nifedipine drug interaction study in normal healthy volunteers demonstrated that coadministration of metformin and nifedipine increased plasma metformin Cmax and AUC by 20 and 9%, respectively, and increased the amount of metformin excreted in the urine. Tmax and half-life of metformin were unaffected. Nifedipine appears to enhance the absorption of metformin. Metformin had minimal effects on the pharmacokinetics of nifedipine.

Pharmacodynamic interactions.

Sulfonylureas.

During concomitant therapy with sulfonylureas, blood glucose should be monitored because combined therapy may cause hypoglycaemia.

Beta-blockers.

Coadministration of metformin and beta-blockers may result in a potentiation of the hypoglycaemic action. In addition, some of the premonitory signs of hypoglycaemia, in particular tachycardia, may be masked. Monitoring of blood glucose should be undertaken during dosage adjustment of either agent.

ACE inhibitors.

ACE-inhibitors may decrease the blood glucose levels. Therefore, dose adjustment of metformin hydrochloride may be necessary when such medicinal products are added or discontinued.

Calcium channel blockers.

Calcium channel blockers may affect glucose control in diabetic patients; regular monitoring of glycaemic control is recommended.

Thyroid products.

Thyroid products tend to produce hyperglycaemia and may therefore lead to loss of control.

Corticosteroids.

Corticosteroids tend to produce hypoglycaemia and may lead to loss of control.

Alcohol.

Alcohol may increase the risk of lactic acidosis in acute intoxication, particularly in the case of fasting or malnutrition, and hepatic insufficiency.
Avoid consumption of alcohol and alcohol containing medication. Alcohol may make the signs of hypoglycaemia less clear, and delayed hypoglycaemia can occur. The CNS depressant effects of alcohol plus hypoglycaemia can make driving or the operation of dangerous machinery much more hazardous. Excessive consumption of alcohol while on metformin may result in elevation of blood lactate.

Diuretics, especially loop diuretics.

May increase the risk of lactic acidosis due to their potential to decrease renal function.

Thiazide diuretics.

Thiazide therapy may impair glucose tolerance. Dosage adjustment of metformin may be required.

Iodinated contrast media.

Formet should be temporarily withheld in patients undergoing radiological studies involving intravascular administration of iodinated contrast materials, because use of such products may result in acute alteration of renal function. (See Section 4.4 Special Warnings and Precautions for Use.)

Organic cation transporters (OCT).

Metformin is a substrate of both transporters OCT1 and OCT2. Coadministration of metformin with:
Substrates/inhibitors of OCT1 (such as verapamil) may reduce efficacy of metformin;
Inducers of OCT1 (such as rifampicin) may increase gastrointestinal absorption and efficacy;
Substrates/inhibitors of OCT2 (such as cimetidine, dolutegravir, crizotinib, olaparib, daclatasvir, vandetanib) may decrease the renal elimination of metformin and thus lead to an increase metformin plasma concentration.

Carbonic anhydrase inhibitors.

Topiramate or other carbonic anhydrous inhibitors (e.g. zonisamide, acetazolamide or dichlorphenamide) frequently cause a decrease in serum bicarbonate and induce non-anion gap, hyperchloremic metabolic acidosis. Concomitant use of these drugs with metformin hydrochloride tablets may increase the risk for lactic acidosis. Consider more frequent monitoring for these patients.

NSAIDS.

May increase the risk of lactic acidosis and adversely affect renal function.
Therefore, caution is advised when these drugs are co-administered with metformin and a dose adjustment may be considered, particularly in patients with renal impairment.

4.6 Fertility, Pregnancy and Lactation

Effects on fertility.

Fertility of male or female rats was unaffected by metformin administration at doses up to 600 mg/kg/day, or approximately twice the maximum recommended human daily dose on a body surface area basis.
(Category C)
To date, no relevant epidemiological data is available. Animal studies do not indicate harmful effects with respect to pregnancy, embryonal or foetal development, parturition or postnatal development.
Since it is important to achieve strict normoglycaemia during pregnancy, metformin should be replaced by insulin.
Metformin was not teratogenic in rats and rabbits at doses up to 600 mg/kg/day, or about two times the maximum recommended human daily dose on a body surface area basis. Determination of foetal concentrations demonstrated a partial placental barrier to metformin. Because animal reproduction studies are not always predictive of human response, any decision to use this drug should be balanced against the benefits and risks. The safety of metformin in pregnant women has not been established.
When the patient plans to become pregnant and during pregnancy, it is recommended that diabetes should not be treated with metformin but insulin should be used to maintain blood glucose levels as close to normal as possible in order to lower the risk of foetal malformations associated with abnormal blood glucose levels.
Studies in lactating rats show that metformin is excreted in milk and reaches levels comparable to those in plasma. Similar studies have not been conducted in nursing mothers, but caution should be exercised in such patients, and a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.

4.7 Effects on Ability to Drive and Use Machines

Metformin monotherapy does not cause hypoglycaemia and therefore has no effect on the ability to drive or to use machinery.
However, patients should be alerted to the risk of hypoglycaemia when metformin is used in combination with other antidiabetic agents (sulphonylureas, glinides, insulin).

4.8 Adverse Effects (Undesirable Effects)

The following undesirable effects may occur under treatment with metformin hydrochloride. Frequencies are defined as follows: very common: > 1/10; common > 1/100, < 1/10; uncommon > 1/1,000, < 1/100; rare > 1/10,000, < 1/1,000; very rare < 1/10,000; not known (cannot be estimated from the available data).
Within each frequency grouping, undesirable effects are presented in order of decreasing seriousness.

Nervous system disorders.

Common: taste disturbance.

Gastrointestinal.

Very common: mild gastrointestinal symptoms such as diarrhoea, nausea, vomiting, abdominal pain and loss of appetite, especially during the initial treatment period. These symptoms are generally transient and resolve spontaneously during continued treatment.
Gastrointestinal side effects can possibly be avoided if Formet is taken with meals and if the dose is increased slowly. Occasionally, a temporary dose reduction can be considered. Occurrence of gastrointestinal symptoms, once a patient is stabilised on any dose of metformin, could be due to lactic acidosis or other serious disease.

Skin and subcutaneous tissue disorders.

Very rare: skin reactions such as erythema, pruritus and urticaria.

Metabolism and nutritional disorder.

Very rare: lactic acidosis (see Section 4.4 Special Warnings and Precautions for Use) is a very rare but serious metabolic complication that can occur due to metformin accumulation during treatment with Formet.
The onset of lactic acidosis is often subtle and accompanied only by nonspecific symptoms such as malaise, myalgia, respiratory distress, increasing somnolence and nonspecific abdominal distress. There may be associated hypothermia, hypotension and resistant bradyarrhythmias with more marked acidosis. The patient and the patient's doctor must be aware of the possible importance of such symptoms and the patient should be instructed to notify the doctor immediately if they occur. Lactic acidosis should be suspected in any diabetic patient with metabolic acidosis lacking evidence of ketoacidosis (ketonuria and ketonaemia).
Lactic acidosis is a medical emergency that must be treated in hospital. In a patient with lactic acidosis who is taking Formet, the drug should be discontinued immediately and general supportive measures should be instituted promptly.

Hepatobiliary disorders.

Very rare: Isolated reports of liver function test abnormalities or hepatitis resolving upon metformin discontinuation.

Dermatological.

Very rare: Mild erythema has been reported in some hypersensitive individuals.

Haematological.

Very rare: A decrease of vitamin B12 absorption with a decrease in serum levels has been observed in patients treated long term with metformin and appears to be generally without clinical significance. Therefore, serum B12 levels should be appropriately monitored and periodic parenteral B12 supplementation considered.

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

Symptoms.

Hypoglycaemia has not been seen with ingestion of up to 85 g of metformin alone, although lactic acidosis has occurred in such circumstances. The onset of lactic acidosis is often subtle and accompanied only by nonspecific symptoms such as malaise, myalgia, respiratory distress, increasing somnolence and nonspecific abdominal distress. There may be associated hypothermia, hypotension and resistant bradyarrhythmias with more marked acidosis. Lactic acidosis should be suspected in any diabetic patient with metabolic acidosis lacking evidence of ketoacidosis (ketonuria and ketonaemia).

Treatment.

Lactic acidosis should be feared in diabetic metformin treated patients with overdose. Lactic acidosis is diagnosed and monitored by measurement of serum electrolytes, arterial pH and pCO2 and arterial lactate plasma level.
The aim of treatment is to manage any underlying disorder and in some cases this will be sufficient to enable the body's homeostatic mechanism to correct the acid-base imbalance. The advantages of more active treatment of the acidosis must be balanced against the risks, including over alkalinisation with sodium bicarbonate. Because metformin hydrochloride is dialysable (with a clearance of up to 170 mL/min under good haemodynamic conditions), prompt haemodialysis is recommended to correct the acidosis and remove the accumulated metformin.
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.

Formet is an oral biguanide hypoglycaemic agent. It causes an increased peripheral uptake of glucose by increasing the biological efficiency of available exogenous or endogenous insulin.
The mode of action of metformin may be linked to an increase of insulin sensitivity. It does not stimulate insulin release but does require the presence of insulin to exert its hypoglycaemic effect. Possible mechanisms of action include inhibition of gluconeogenesis in the liver, delay in glucose absorption from the gastrointestinal tract and an increase in peripheral uptake of glucose.
Metformin has an antiketogenic activity which is comparable, though somewhat inferior, to insulin itself.
Metformin lowers both basal and postprandial blood glucose in diabetic patients but does not cause hypoglycaemia in either diabetics or normal individuals.

Clinical trials.

A randomised, open label bioequivalence study in 18 healthy volunteers showed, on the basis of Cmax and AUC determinations, that one Formet 500 mg tablet is bioequivalent to one Diabex 500 mg tablet. The calculated ratio of geometric means and 90% confidence intervals for Cmax and AUC0-∞ were 0.861 (0.864-1.127) and 0.912 (0.918-1.103), respectively. The 90% confidence intervals were within the limits 0.80-1.25, as required to conclude bioequivalence. Since these two formulations are shown to be bioequivalent, therefore they may be used interchangeably.

5.2 Pharmacokinetic Properties

Absorption.

After oral administration, metformin hydrochloride is absorbed along the entire gastrointestinal mucosa. Studies using single oral doses of metformin tablets indicate that there is a lack of dose proportionality with increasing doses, which is due to decreased absorption rather than an increase in elimination. After oral administration, metformin absorption is saturable and incomplete. It is assumed that the pharmacokinetics of metformin absorption are nonlinear.
At usual clinical doses and dosing schedules of metformin tablets, steady-state plasma concentrations are reached in 24 to 48 hours and are generally less than 1 microgram/mL. During controlled clinical trials, maximum metformin plasma levels did not generally exceed 5 microgram/mL, even at maximum doses.

Distribution.

Metformin is not bound to plasma proteins.

Metabolism.

Metformin is excreted unchanged in the urine and does not undergo hepatic metabolism.

Excretion.

In patients with decreased renal function (based on measured creatinine clearance), the plasma half-life of metformin is prolonged and renal clearance is decreased in proportion to the decrease in creatinine clearance, e.g. if creatinine clearance is 10-30 mL/min, renal clearance is reduced to 20% of normal.

5.3 Preclinical Safety Data

Genotoxicity.

No evidence of a mutagenic potential of metformin was found in the Ames test (S. typhimurium), gene mutation test (mouse lymphoma cells), chromosomal aberrations test (human lymphocytes), or in vivo micronuclei test (mouse bone marrow).

Carcinogenicity.

Long term carcinogenicity studies have been performed in rats (dosing duration of 104 weeks) and mice (dosing duration of 91 weeks) at doses up to and including 900 mg/kg/day and 1500 mg/kg/day, respectively. These doses are both approximately two to three times the recommended human daily dose on a body surface area basis. No evidence of carcinogenicity with metformin was found in either male or female mice. Similarly, there was no tumourigenic potential observed with metformin in male rats. However, an increased incidence of benign stromal uterine polyps was seen in female rats treated with 900 mg/kg/day.

6 Pharmaceutical Particulars

6.1 List of Excipients

The tablets contain the following excipients: povidone, magnesium stearate and Opadry Clear OY-29020.

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 30⁰C.

6.5 Nature and Contents of Container

Formet 250.

Bottles and blister packs of 10* and 100* tablets.

Formet 500.

Bottles of 10* and 100 tablets and PVC/PVDC/Aluminium blister packs of 10*, 20* and 100 tablets.

Formet 850.

Bottles* and PVC/PVDC/Aluminium blister packs of 10* and 60 tablets.

Formet 1000.

Bottles and blister packs of 10*, 15*, 60*, 90 and 100* tablets.
*These pack sizes are not 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

Chemical structure.

The chemical name for metformin hydrochloride is 1,1 dimethyl biguanide hydrochloride. Its structural formula is:
C4H11N5.HCl. Molecular weight: 165.6.
Metformin hydrochloride is a white, crystalline powder which is odourless or almost odourless and hygroscopic. It is freely soluble in water, slightly soluble in ethanol (96%), and practically insoluble in chloroform and ether.

CAS number.

1115-70-4.

7 Medicine Schedule (Poisons Standard)

S4.

Summary Table of Changes