How does it work?

Glucophage tablets and Glucophage SR tablets both contain theactive ingredient metformin hydrochloride. (NB. Metformin is also availablewithout a brand name, ie as thegeneric medicine.) Metformin is used to help controlblood sugar levels in people with type 2 or non-insulin dependent diabetes(NIDDM).

People with diabetes have a deficiency or absence of a hormoneproduced by the pancreas called insulin. Insulin is the main hormoneresponsible for the control of sugar in the blood. In type 2 diabetes thepancreas does not produce sufficient insulin and the cells of the body areresistant to the low levels of insulin circulating in the blood. Insulin wouldnormally make the cells remove sugar from the blood, hence in type 2 diabetesblood sugar levels can rise too high.

Metformin hydrochloride is a type of antidiabetic medicine knownas a biguanide. It works in a number of ways to decrease the amount of sugar inthe blood of people with type 2 diabetes.

Firstly, it reduces the amount of sugar produced by cells in theliver. Secondly, it increases the sensitivity of muscle cells to insulin. Thisenables the cells to remove sugar from the blood more effectively. Finally, italso delays absorption of sugar from the intestines into the bloodstream aftereating. Overall, metformin reduces blood sugar levels both between and directlyafter meals.

Metformin is used as a first line treatment of type 2 diabetesin people who are overweight. It is used when diet and exercise have failed tocontrol blood sugar levels. It can also be used in combination with otherantidiabetic medicines to provide better control of blood sugar.

Glucophage tablets are standard release tablets that are takentwo or three times a day either during or just after meals.

Glucophage SR tablets are prolonged release tablets that aredesigned to release metformin slowly and continuously over several hours. Thisproduces a steady blood level of the medicine throughout the day. The tabletsare designed to be taken once or twice a day with meals, depending on yourblood sugar control. They must be swallowed with water and not broken, chewedor crushed, as this would damage the prolonged release action.

What is it used for?

• Type 2 (non-insulin dependent) diabetes, when diet alone has failed to fully control blood sugar.
• Polycystic ovary syndrome (unlicensed use).

Warning!

• Your doctor may want you to check your blood sugar level from time to time while you are taking this medicine. Make sure you discuss how to do this and how often with your GP, pharmacist or diabetes specialist.
• When used on its own, metformin does not usually cause low blood sugar levels (hypoglycaemia). However, you may get low blood sugar if you take metformin in combination with other antidiabetic medicines. If this applies to you, you should make sure that you are aware of the symptoms of hypoglycaemia (these may include cold sweats, cool pale skin, tremor, anxious feeling, unusual tiredness or weakness, confusion, difficulty in concentration, excessive hunger, temporary vision changes, headache or nausea) and what to do if you experience these symptoms. Discuss this with your GP, pharmacist or diabetes specialist.
• Metformin can cause a rare but serious condition called lactic acidosis, which is an excess of lactic acid in the blood. It is more likely to occur in people with decreased kidney function. Drinking excessive amounts of alcohol, particularly on an empty stomach or if you have liver problems, can also increase the risk of lactic acidosis. Your doctor will monitor you for this side effect, but symptoms that might indicate its development include rapid and/or deep breathing and non-specific symptoms such as feeling weak, sick or generally unwell, vomiting, abdominal pain, or unusual muscle pains or discomfort. You should stop taking this medicine and consult your doctor if you experience any of these.
• Your kidney function should be monitored regularly while you are taking this medicine. Your doctor will usually want to check your kidney function once or twice a year, or more frequently if you are elderly or have any existing kidney problems.
• Your doctor will ask you to stop taking this medicine temporarily if you are going to have a certain type of X-ray involving an injection of iodinated dye (contrast agent). Tell your doctor that you are taking metformin if you are due to have this type of X-ray. You should not start taking this medicine again until 48 hours after the X-ray, and only after your kidney function has been tested and found to be normal.
• Consult your doctor about your diabetes treatment if you are due to have surgery under a general anaesthetic. In these situations blood sugar is normally controlled by insulin, so your doctor may ask you to stop taking this medicine 48 hours before surgery.
• The shells of Glucophage SR tablets may pass through your gut undigested and be visible in your faeces. This is normal.

Not to be used in

• Diabetic keto-acidosis.
• Diabetic pre-coma (due to ketoacidosis in severe and inadequately treated diabetes).
• People with decreased kidney function or kidney failure.
• People with decreased liver function.
• Dehydration.
• People with severe infections or sepsis.
• People with reduced blood flow to vital internal organs (shock).
• People with conditions that cause breathing to be ineffective, ie to not effectively oxygenate the blood or remove carbon dioxide from the lungs (respiratory failure).
• Heart failure.
• People who have recently had a heart attack.
• Alcohol intoxication.
• Alcoholism.
• Children under ten years of age.

This medicine should not be used if you are allergic to one orany of its ingredients. Please inform your doctor or pharmacist if you havepreviously experienced such anallergy. If you feel you haveexperienced an allergic reaction, stop using this medicine and inform yourdoctor or pharmacist immediately.

Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy orbreastfeeding. However, other medicines may be safely used in pregnancy orbreastfeeding providing the benefits to the mother outweigh the risks to theunborn baby. Always inform your doctor if you are pregnant or planning apregnancy, before using any medicine.

• The manufacturer recommends that this medicine is not used during pregnancy. If you get pregnant while taking this medicine, or are planning a pregnancy, you should seek medical advice from your doctor. Control of diabetes mellitus in pregnancy is usually achieved using insulin, because this provides a more stable control of blood sugar. However, metformin may be used either on its own, or in combination with insulin, for women with pre-existing diabetes or pregnancy diabetes. This is a recommendation from the National Institute for Clinical Excellence (NICE) 2008 guidance on treating diabetes in pregnancy, which states that there is strong evidence for the safety and effectiveness of using metformin during pregnancy.
• This medicine may pass into breast milk in small amounts. The manufacturer recommends that it is not used during breastfeeding. However, if you were taking metformin for type 2 diabetes before you got pregnant, it is considered safe to continue to take it while you are breastfeeding. This is another recommendation from the 2008 NICE guideline. Seek further medical advice from your doctor.

Label warnings

• Take this medication with or after food.

Side effects

Medicines and their possible side effects can affect individualpeople in different ways. The following are some of the side effects that areknown to be associated with this medicine. Just because a side effect is statedhere does not mean that all people using this medicine will experience thator any side effect.

Very common (affect more than 1 in 10 people)

• Disturbances of the gut such as nausea, vomiting, diarrhoea or abdominal pain.
• Loss of appetite.

Common (affect between 1 in 10 and 1 in 100 people)

• Taste disturbance, usually a metallic taste.

Very rare (affect less than 1 in 10,000 people)

• Elevated levels of lactic acid in the blood (lactic acidosis).
• Decreased absorption of vitamin B12 during long-term use.
• Skin reactions such as rash, itching or flushing.

The side effects listed above may not include all of the sideeffects reported by the medicine'smanufacturer.For moreinformation about any other possible risks associated with this medicine,please read the information provided with the medicine or consult your doctoror pharmacist.

How can this medicine affect other medicines?

It is important to tell your doctor or pharmacist what medicinesyou are already taking, including those bought without a prescription andherbal medicines, before you start treatment with this medicine. Similarly,check with your doctor or pharmacist before taking any new medicines whiletaking this one, to ensure that thecombination is safe.

When metformin is taken with other antidiabetic medicines, suchas sulphonylureas (eg gliclazide, glibenclamide) or insulin, there will be anenhanced blood sugar lowering effect. Your blood sugar level should bemonitored if you are taking metformin in combination with other antidiabetic medicines.

The following medicines may increase blood glucose levels. Ifyou start treatment with any of these your doctor may want to check your blood sugar level more frequently and your dose of metformin may needincreasing:

• beta-2-agonists, such as salbutamol
• corticosteroids, such as prednisolone
• diuretics, especially thiazide diuretics, eg bendroflumethiazide
• lithium
• oestrogens and progesterones, such as those contained in oral contraceptives.

Octreotide and lanreotide may also affect blood sugar levels. If you are being treated with one of these medicines your doctor may want to check your blood sugar levels and adjust your metformin dose if necessary.

Low blood sugar levels (hypoglycaemia) may occur, sometimesunpredictably, if ACE inhibitors such as captopril are taken withmetformin. Your doctor may want you to temporarily check your blood sugar more frequently if you start treatment with an ACE inhibitor while taking metformin.

MAOI antidepressants, such as phenelzine, tranylcypromine or isocarboxazid, may enhance the blood sugar lowering effect of metformin. Your doctor may ask you to monitor your blood sugar more frequently if you are prescribed an MAOI antidepressant with this medicine.

Cimetidine may cause an increase in the blood level ofmetformin. Your doctor may reduce your metformin dose if you take bothmedicines.

Metformin should be stopped before X-ray examinations involvinginjections of iodinated contrast materials, as these may cause a temporarydecrease in kidney function that could affect the blood level of metformin.Metformin should not be started again after the X-ray until kidney function hasbeen tested and found to be normal.

A drop in the number of blood cells called platelets in the blood has been seen in some people taking the antihistamine ketotifen in combination with metformin. The manufacturer of ketotifen recommends that it should be avoided in people taking metformin.

Other medicines containing the same active ingredient

Metformin standard release tablets and liquid are also availablewithout a brand name, ie as thegeneric medicine.