Review Drug

Metformin

Brand names Glucophage, Glucamet, Orabet

General Information

Metformin is an antidiabetic drug. Taken by mouth, the drug is used to treat adult (maturity-onset) diabetes in which some insulin-secreting cells are still active in the pancreas, and is usually prescribed for obese patients.

It lowers blood sugar by reducing the absorption of glucose from the digestive tract into the bloodstream; by reducing the glucose production by cells in the liver and kidneys; and by increasing the sensitivity of cells to insulin so that they take up glucose more effectively from the blood.

The drug is given in conjunction with a special diabetic diet that limits the intake of sugar and fats. Metformin is often given with another antidiabetic drug that stimulates insulin secretion by the pancreas.

Information for Users

Your drug prescription is tailored for you. Do not alter dosage without checking with your doctor.

How taken

Tablets.

Frequency and timing of doses

2-3 x daily with food.

Adult dosage range

1.5-3g daily.

Onset of effect

Within 2 hours. It may take 2 weeks to achieve control of diabetes.

Duration of action

8-12 hours.

Diet advice

An individualized low-fat, low-sugar diet must be maintained in order for the drug to be fully effective. Follow your doctor’s advice.

Storage

Keep in a closed container in a cool, dry place out of the reach of children.
Missed dose

Take as soon as you remember. If your next dose is due within 2 hours, take a single dose now and skip the next.

Stopping the drug

Do not stop taking the drug without consulting your doctor; stopping the drug may lead to worsening of the underlying condition.

Overdose Action
Seek immediate medical advice in all cases. Take emergency action if fits or loss of consciousness occur.

Possible Adverse Effects
Minor gastrointestinal symptoms such as nausea, vomiting, and loss of appetite are often helped by taking the drug with food. Diarrhoea usually settles after a few days of continued treatment. Symptoms such as dizziness, sweating, weakness, confusion, and a rash require prompt medical attention because they could indicate an excessive lowering of blood sugar.

Interactions

General note
A number of drugs reduce the effects of metformin. These include corticosteroids, oestrogens, and diuretics.
Other drugs, notably monoamine oxidase inhibitors (MAOIs) and beta blockers, increase its effects.

Quick Reference

Drug group Antidiabetic drug 

Overdose danger rating High
Dependence rating Low
Prescription needed Yes
Available as generic Yes

Special Precautions

Be sure to tell your doctor if:

You have long-term liver or kidney problems.

You have heart failure.   You are a heavy drinker.

You are taking other medications.

Pregnancy

Not usually prescribed. Insulin is usually substituted because it provides better diabetic control during pregnancy. Discuss with your doctor.

Breast-feeding

Safety not established. Discuss with your doctor.
 
Infants and children

Not recommended.
 
Over 60

  Increased likelihood of adverse effects. Reduced dose may therefore be necessary.

Driving and hazardous work

Usually no problems. Avoid such activities if you have warning signs of low blood sugar.

Alcohol

Avoid. Alcohol increases the risk of low blood sugar, and can cause coma by increasing the acidity of the blood.

Surgery and general anaesthetics

Surgery may reduce the response to this drug. Notify your doctor that you are diabetic before any surgery; insulin treatment may need to be substituted.

 Prolonged Use

Prolonged treatment with metformin can deplete reserves of vitamin B12, and this may cause anaemia.

Monitoring
Regular checks on levels of sugar in the urine and/or blood are usually required. Vitamin B12 levels may also be checked annually.