Consumer medicine information

Metformin GH

Metformin hydrochloride

BRAND INFORMATION

Brand name

Metformin GH

Active ingredient

Metformin hydrochloride

Schedule

S4

 

Consumer medicine information (CMI) leaflet

Please read this leaflet carefully before you start using Metformin GH.

What is in this leaflet

This leaflet answers some common questions about medicine.

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 benefits and risks. Your doctor has weighed the risks of you taking this medicine against the benefits expected for you.

If you have any concerns about taking this medicine, talk to your doctor, pharmacist or diabetes educator.

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

What METFORMIN GH is used for

It is used to control blood glucose (the amount of sugar in the blood) in people with diabetes mellitus.

It can be used in type 2 diabetes 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 high 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 2 diabetes.

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

It is available only with a doctor's prescription.

There is no evidence it is addictive.

How it works

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

People with type 2 diabetes are unable to make enough insulin or their body does not respond properly to the insulin it does make. This causes a build up of glucose in the blood, which can lead to serious medical problems.

Long-term hyperglycaemia can lead to heart disease, blindness, kidney damage, poor blood circulation and gangrene.

Signs of hyperglycaemia may include:

  • tiredness or lack of energy;
  • headache;
  • thirst;
  • passing large amounts of urine;
  • blurred vision.

Before you take METFORMIN GH

When you must not take it

Do not take it if you are allergic to:

  • medicines containing metformin or any other biguanide;
  • any of the ingredients listed at the end of this leaflet.

Some of the symptoms of an allergic reaction may include skin rash, itching or hives; swelling of the face, lips or tongue which may cause difficulty in swallowing or breathing; wheezing or shortness of breath.

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

  • type 1 diabetes mellitus that is well controlled by insulin alone;
  • type 2 diabetes that is already well controlled by diet alone;
  • any type of metabolic acidosis such as lactic acidosis, diabetic 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 severe kidney disease;
  • dehydration, severe blood loss, shock;
  • a 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 it 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 it for a certain period of time before and after the examination or the 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 this medicine if you are pregnant or plan to become pregnant. The safety of Metformin GH in pregnant women has not been established.

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

Do not take this medicine if you are breastfeeding. Metformin GH is not recommended while you are breastfeeding. Your doctor will discuss the options available to you.

Do not take this medicine after the expiry date printed on the pack or if the packaging is torn or shows signs of tampering. If it has expired or is damaged, return it to your pharmacist for disposal.

If you are not sure whether you should start taking this medicine ask your doctor.

Before you start to take it

Tell your doctor if you have allergies to any other medicines, foods, dyes or preservatives.

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

  • heart failure;
  • kidney problems.

Your doctor may want to take special care if you have any of these conditions.

Tell your doctor if you drink alcohol. Alcohol can affect the control of your diabetes. Drinking excessive amounts of alcohol while you are being treated with this medicine may also lead to serious side effects. Your doctor may suggest you stop drinking or reduce the amount of alcohol you drink.

If you have not told your doctor about any of the above, tell them before you start taking this.

Taking other medicines

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

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

  • other medicines used to treat diabetes;
  • medicines that contain alcohol, such as cough and cold syrups;
  • 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 betablockers, calcium channel blockers and ACE inhibitors;
  • medicines used to prevent blood clots, such as warfarin;
  • diuretics, also called fluid tablets;
  • 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 prednisone or cortisone;
  • some medicines used to treat asthma such as salbutamol or terbutaline;
  • medicines that are substrates/inhibitors of organic cation transporters - OCT 1 such as verapamil; OCT 2 such as dolutegravir, crizotinib, olaparib, daclatasvir or vandetanib;
  • medicines that are inducers of OCT 1 such as rifampicin.
  • medicines that may increase the risk of lactic acidosis when concomitantly used with metformin hydrochloride such as topiramate and other carbonic anhydrase inhibitors

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

Your doctor and pharmacist have more information on medicines to be careful with or avoid while taking this medicine.

How to take METFORMIN GH

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

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

How much to take

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

The usual starting dose for adults is 500 mg one to two times a day. Your doctor may increase or decrease the dose, depending on your blood glucose levels. The maximum recommended dose is 1000 mg three times a day.

The elderly and people with kidney problems may need smaller doses.

Children and Adolescents

The usual starting dose for children from 10 years of age and adolescents is one tablet of 500 mg or 850 mg once daily. Your doctor may increase or decrease the dose, depending on your blood glucose levels.

The maximum recommended dose is 2 g taken as two or three divided doses.

If your child has diabetes that is resistant to insulin and is being treated in hospital, your child's doctor will decide the dose.

How to take it

Swallow the tablets with a glass of water.

The 1000 mg tablets can be divided in half along the breakline, if advised by your doctor or pharmacist.

When to take it

Take Metformin GH during or immediately after food. This will reduce the chance of a stomach upset.

Take your medicine 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.

How long to take it

Continue taking your medicine for as long as your doctor tells you to.

This medicine helps control diabetes but does not cure it. Most people will need to take this on a long-term basis.

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 the missed dose as soon as you remember (with food), and then go back to taking your tablets as you would normally.

Do not take a double dose to make up for the dose you missed. 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) for advice, or go to Accident and Emergency at the nearest hospital, if you think you or anyone else may have taken too much medicine. Do this even if there are no signs of discomfort or poisoning.

If you take too much Metformin GH, you may feel sleepy, feel very tired, feel sick, vomit, have trouble breathing and have unusual muscle pain, stomach pain or diarrhoea. These may be early signs of a serious condition called lactic acidosis (build up of lactic acid in the blood). You may also experience symptoms of hypoglycaemia (low blood glucose). This usually only happens if you take too much of this together with other medicines for diabetes or with alcohol.

If you do experience any signs of hypoglycaemia, raise your blood glucose quickly by eating jelly beans, sugar or honey, drinking a non-diet soft drink or taking glucose tablets.

While you are taking it

Things you must do

Make sure that you, your friends, family and work colleagues can recognise the symptoms of hypoglycaemia and hyperglycaemia and know how to treat them.

HYPOGLYCAEMIA

Metformin GH 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;
  • light-headedness, 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-ordination;
  • slurred speech;
  • confusion;
  • fits or loss of consciousness.

If you experience any of the symptoms of hypoglycaemia, 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 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 notice the return of any of the signs of hyperglycaemia, contact your doctor immediately.

Your doctor may need to consider additional or other treatments for your diabetes. The risk of hyperglycaemia is increased in the following situations:

  • uncontrolled diabetes;
  • illness, infection or stress;
  • taking less medicine than prescribed;
  • taking certain other medicines;
  • too little exercise;
  • eating more carbohydrates than normal.

Tell your doctor if you:

  • become ill;
  • become dehydrated;
  • are injured;
  • have a fever;
  • have a serious infection;
  • are having surgery (including dental surgery).

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 this with insulin.

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

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

If you become pregnant while taking Metformin GH, 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 an 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 this 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 this medicine.

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 this, 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 take this medicine to treat any other complaints unless your doctor tells you to.

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

Do not skip meals while taking this medicine.

Do not stop taking your medicine or change the dosage without checking with your doctor.

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, this medicine by itself is unlikely to affect how you drive or operate machinery.

If you become 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 sick days.

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

  • wear some form of identification (eg. bracelet) 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;
  • bring enough of this medicine with you, so you don't miss any doses.

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. Warning signs are:

  • 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 this.

This helps most people with diabetes but it may have unwanted side effects in some people.

All medicines can have side effects. Sometimes they are serious, most of the time they are not. You may need medical attention 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.

Do not be alarmed by the following list of side effects. You may not experience any of them.

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

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

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

These are generally mild side effects which disappear after the first few weeks. Taking this medicine with meals can help reduce stomach pain, nausea and diarrhoea. Skin reactions have been reported rarely.

Tell your doctor immediately or go to Accident and Emergency at the nearest hospital if you notice any of the following symptoms of lactic acidosis (build-up of lactic acid in the blood):

  • nausea, vomiting, stomach pain;
  • trouble breathing;
  • feeling weak, tired or generally unwell;
  • unusual muscle pain;
  • sleepiness;
  • dizziness or light-headedness;
  • shivering, feeling extremely cold;
  • slow heartbeat.

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 (eg. reduced vitamin B12 level) can only be found when your doctor does tests from time to time to check your progress.

After taking METFORMIN GH

Storage

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

Keep your tablets in a cool dry place where the temperature stays below 25°C.

Do not store this medicine or any other medicine in the bathroom or near a sink. Do not leave it in the car or on a window sill. 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 taking this medicine or the expiry date has passed, ask your pharmacist what to do with any medicine that is left over.

Product description

What it looks like

Metformin GH tablets come in 3 strengths:

  • 500 mg - white, film-coated, round, biconvex tablets debossed with ‘500’ on one side and plain on the other side. Supplied in blister packs of 100 tablets.
  • 850 mg - white, film-coated, round, biconvex tablets debossed with ‘850’ on one side and plain on the other side. Supplied in blister packs of 60 tablets.
  • 1000 mg- white to off-white, film-coated, oval shaped tablets debossed with ‘10’ and ‘00’ on either side of deep notch on one side and breakline on other side.

Not all presentations or pack sizes may be marketed.

Ingredients

The active ingredient in Metformin GH is metformin hydrochloride.

The tablets also contain the following inactive ingredients:

  • colloidal anhydrous silica;
  • maize starch;
  • propylene glycol;
  • purified talc;
  • sodium starch glycollate type A;
  • titanium dioxide;
  • povidone;
  • magnesium stearate;
  • hypromellose;
  • macrogol 6000.

The tablets are gluten free.

Australian Registration Numbers

500 mg - AUST R 284971

850 mg - AUST R 284973

1000 mg - AUST R 284975

Sponsor

Generic Health Pty Ltd
Suite 2, Level 2
19-23 Prospect Street
Box Hill, VIC, 3128
Australia

E-mail: [email protected]
Telephone: +61 3 9809 7900
Website: www.generichealth.com.au

This leaflet was prepared in October 2021.

Published by MIMS January 2022

BRAND INFORMATION

Brand name

Metformin GH

Active ingredient

Metformin hydrochloride

Schedule

S4

 

1 Name of Medicine

Metformin hydrochloride.

2 Qualitative and Quantitative Composition

Each Metformin GH 500 mg tablet contains 500 mg of metformin hydrochloride. Each Metformin GH 850 mg tablet contains 850 mg of metformin hydrochloride. Each Metformin GH 1000 mg tablet contains 1000 mg of metformin hydrochloride.
For the full list of excipients, see Section 6.1 List of Excipients.

3 Pharmaceutical Form

Metformin GH 500 mg.

White, film-coated, round, biconvex tablets debossed with "500" on one side and plain on the other side.

Metformin GH 850 mg.

White, film-coated, round, biconvex tablets debossed with "850" on one side and plain on the other side.

Metformin GH 1000 mg.

White to off-white, film-coated, oval shaped, biconvex tablets debossed with '10' and '00' on either side of deep notch on one side and breakline on other side.

4 Clinical Particulars

4.1 Therapeutic Indications

Metformin is indicated in the treatment of type 2 diabetes mellitus in adults, children from 10 years of age and adolescents, particularly in overweight patients, when dietary management and exercise alone does not result in adequate glycaemic control.
For adult patients, metformin may be used as initial treatment or in sulfonylurea failures either alone or in combination with a sulfonylurea and other oral agents or as adjuvant therapy in insulin requiring type 2 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 the use of high doses of metformin above 2 g per day.
It is important that the tablets are taken in divided doses with meals.
Half tablet doses of the 1000 mg tablet may be administered, if care is taken not to crush or chew the tablets.
Initially 500 mg should be taken once or twice a day and if necessary increased over a few weeks up to 1 g (1000 mg) 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 (1000 mg) 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.
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 metformin 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 metformin 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.

Use in children and adolescents.

Metformin can be used as monotherapy in children from 10 years of age and adolescents. The usual starting dose is one tablet of 500 mg or 850 mg once daily, given during meals or after meals.
After 10 to 15 days the dose should be adjusted on the basis of blood glucose measurements. A slow increase of dose may improve gastrointestinal tolerability.
The maximum recommended dose of metformin is 2 g daily, taken as two or three divided doses.

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.
Any type of metabolic acidosis (such as lactic acidosis, diabetic ketoacidosis).
Hypersensitivity to metformin hydrochloride or to any of the excipients.
Diabetic pre-coma.
Renal failure or renal dysfunction (creatinine clearance < 60 mL/min).
Acute conditions with the potential to alter renal function such as: dehydration; severe infection; shock; intravascular administration of iodinated contrast materials (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 that can occur due to metformin accumulation. Reported cases of lactic acidosis in patients on metformin have occurred primarily in diabetic patients with significant renal failure. The incidence of lactic acidosis can and should be reduced by assessing other associated risk factors such as poorly controlled diabetes, ketosis, prolonged fasting, excessive alcohol intake, hepatic insufficiency and any condition associated with hypoxia.

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).

Renal function.

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 anti-inflammatory drug (NSAID).

Administration of iodinated contrast materials.

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 4.4 Special Warnings and Precautions for Use; 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 re-evaluated and found to be normal.

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.

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.

Metformin is not recommended for use in children under 10 years of age.
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 prepubescent children, is recommended.

Effects on laboratory tests.

No available data.

4.5 Interactions with Other Medicines and Other Forms of Interactions

Contraindicated combinations.

Iodinated contrast materials.

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 (see Section 4.4 Special Warnings and Precautions for Use, Administration of iodinated contrast materials).

Inadvisable combinations.

Alcohol.

Increased risk of lactic acidosis in acute alcohol intoxication, particularly in case of: fasting or malnutrition; hepatic insufficiency.
Avoid consumption of alcohol and alcohol-containing medications. 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.

Combinations requiring precautions for use.

Medicinal products with intrinsic hyperglycaemic activity (e.g. glucocorticoids and tetracosactides (systemic and local routes), beta-2-agonists, danazol, chlorpromazine at high dosages of 100 mg per day and diuretics).

More frequent blood glucose monitoring may be required, especially at the beginning of treatment. If necessary, adjust the metformin dosage during therapy with the respective medicinal product and upon discontinuation.

Diuretics, especially loop diuretics.

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

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.

Beta-blockers.

Co-administration of metformin and beta-blockers may result in a potentiation of the anti-hyperglycaemic 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.

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 co-administration 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.

Organic cation transporters (OCT).

Metformin is a substrate of both transporters OCT1 and OCT2. Co-administration 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 anhydrase 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 tablet may increase the risk for lactic acidosis. Consider more frequent monitoring of these patients.

NSAID.

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 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.
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.
Australian Categorisation Definition of Category C: Drugs which, owing to their pharmacological effects, have caused or may be suspected of causing, harmful effects on the human fetus or neonate without causing malformations. These effects may be reversible. Accompanying texts should be consulted for further details.
Metformin is excreted into milk in lactating rats. Similar data are not available in humans and a decision should be made whether to discontinue breastfeeding or to discontinue metformin, 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 disorders.

Very Common: Gastrointestinal disorders such as diarrhoea, nausea, vomiting, abdominal pain and loss of appetite. These undesirable effects occur most frequently during initiation of therapy and resolve spontaneously in most cases. To prevent them, it is recommended that metformin be taken in 2 or 3 daily doses during or after meals. A slow increase of the dose may also improve gastrointestinal tolerability.

Skin and subcutaneous tissue disorders.

Very Rare: Skin reactions such as erythema, pruritus and urticaria.

Metabolism and nutrition disorders.

Very Rare: Lactic acidosis (see Section 4.4 Special Warnings and Precautions for Use).
Decrease of vitamin B12 absorption with a decrease in serum levels has been observed in patients treated long-term with metformin. Consideration of such an aetiology is recommended if a patient presents with megaloblastic anaemia. Therefore, serum B12 levels should be appropriately monitored or periodic parenteral B12 supplementation should be considered (see Section 4.4 Special Warnings and Precautions for Use, Other precautions).

Hepatobiliary disorders.

Very Rare: Isolated reports of liver function test abnormalities or hepatitis resolving upon metformin discontinuation.
In clinical trials in children and adolescents with type 2 diabetes, the profile of adverse reactions was similar to that observed in adults.

Reporting suspected adverse reactions.

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. This disorder is a medical emergency and must be treated in hospital. The onset of lactic acidosis is often subtle and accompanied only by non-specific symptoms such as malaise, myalgia, respiratory distress, increasing somnolence and non-specific 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 may develop 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.

Metformin is a biguanide with antihyperglycaemic effects, lowering both basal and postprandial plasma glucose. It does not stimulate insulin secretion and therefore does not produce hypoglycaemia.
Metformin may act via 3 mechanisms:
1. Reduction of hepatic glucose production by inhibiting gluconeogenesis and glycogenolysis.
2. In muscle, by increasing insulin sensitivity, improving peripheral glucose uptake and utilisation.
3. Delay of intestinal glucose absorption.
Metformin stimulates intracellular glycogen synthesis by acting on glycogen synthase.
Metformin increases the transport capacity of all types of membrane glucose transporters (GLUT).
In humans, independently of its action on glycaemia, metformin has favourable effects on lipid metabolism. This has been shown at therapeutic doses in controlled, medium-term or long-term clinical studies: metformin reduces total cholesterol, LDL cholesterol and triglyceride levels.

Clinical trials.

The prospective randomised (UKPDS) study has established the long-term benefit of intensive blood glucose control in type 2 diabetes.
Analysis of the results for overweight patients treated with metformin after failure of diet alone showed:
a significant reduction of the absolute risk of any diabetes-related complication in the metformin group (29.8 events/1,000 patient-years) versus diet alone (43.3 events 1,000 patient-years), p=0.0023, and versus the combined sulfonylurea and insulin monotherapy groups (40.1 events/1,000 patient-years), p=0.0034;
a significant reduction of the absolute risk of diabetes-related mortality: metformin 7.5 events/1,000 patient-years, diet alone 12.7 events/1,000 patient-years, p=0.017;
a significant reduction of the absolute risk of overall mortality: metformin 13.5 events/1,000 patient-years versus diet alone 20.6 events/1,000 patient-years (p=0.011), and versus the combined sulfonylurea and insulin monotherapy groups 18.9 events/1,000 patient-years (p=0.021);
a significant reduction in the absolute risk of myocardial infarction: metformin 11 events/1,000 patient-years, diet alone 18 events/1,000 patient-years (p=0.01).
Benefit regarding clinical outcome has not been shown for metformin hydrochloride used as second line therapy, in combination with a sulfonylurea.
In type 1 diabetes, the combination of metformin and insulin has been used in selected patients, but the clinical benefit of this combination has not been formally established.

Paediatrics.

In a double blind, placebo-controlled study in 82 paediatric patients aged 10 to 16 years with type 2 diabetes (mean FPG 10.1 mmol/L), treatment with metformin (up to 2,000 mg/day) for up to 16 weeks (mean duration of treatment 11 weeks) resulted in a significant mean net reduction in FPG of 3.6 mmol/L, compared with placebo.

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 non-linear.
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.
A randomised, open-label bioequivalence study in 16 healthy volunteers showed, on the basis of Cmax and AUC determinations, that one tablet of metformin hydrochloride 1000 mg can replace two tablets of metformin hydrochloride 500 mg. The relative bioavailability of metformin Hydrochloride 1000 mg compared to metformin hydrochloride 500 mg tablets is 92.6% for AUC and 88% for Cmax.

Paediatrics.

Following an oral dose, children 12 years and older, have shown similar pharmacokinetic profile of metformin to that observed in adults. Pharmacokinetic data in children between 10 and 12 years are not available.

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 formation 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: colloidal anhydrous silica, maize starch, propylene glycol, purified talc, sodium starch glycollate type A, titanium dioxide, povidone, magnesium stearate, hypromellose and macrogol 6000. The tablets are gluten free.

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

Metformin GH 500 mg.

Available in PVC/PVDC/Al blister packs of 10, 14, 20, 28, 30, 56, 60 and 100 tablets.*

Metformin GH 850 mg.

Available in PVC/PVDC/Al blister packs of 10, 14, 20, 28, 30, 56, 60 and 100 tablets.*

Metformin GH 1000 mg.

Available in PVC/PVDC/Al blister packs of 10, 14, 20, 28, 30, 56, 60, 90 and 100 tablets.*
*Not all presentations or pack sizes may be marketed.

Australian registration numbers.

Metformin GH 500 mg: AUST R 284971.
Metformin GH 850 mg: AUST R 284973.
Metformin GH 1000 mg: AUST R 284975.

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

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 in ether.

Chemical structure.


Chemical Name: 1,1-dimethylbiguanide hydrochloride.
Molecular Formula: C4H11N5,HCl.
Molecular Weight: 165.62.

CAS number.

1115-70-4.

7 Medicine Schedule (Poisons Standard)

S4 - Prescription Only Medicine.

Summary Table of Changes