BMA Concise Guide to Medicine & Drugs

Tolbutamide

Brand name None

Used in the following combined preparations None

QUICK REFERENCE

Drug group Drug for diabetes

Overdose danger rating High

Dependence rating Low

Prescription needed Yes

Available as generic Yes

GENERAL INFORMATION

Tolbutamide belongs to a group of drugs known as sulphonylureas, but is shorter acting than many in this group. It is used to treat Type 2 diabetes, and works by stimulating the cells in the pancreas to produce insulin; it will only work, therefore, if functioning cells remain. For this reason, it is not effective in Type 1 diabetes, in which functioning cells are lacking. It may also be given to people with impaired kidney function because it is less likely to build up in the body and excessively lower blood sugar. If additional control of blood glucose is needed, other oral drugs for diabetes, such as metformin or acarbose, can be added to tolbutamide.

As with other oral drugs for diabetes, tolbutamide may need to be replaced with insulin during serious illnesses, injury, or surgery, when diabetic control is lost.

INFORMATION FOR USERS

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

How taken/used Tablets.

Frequency and timing of doses Taken with meals either once daily in the morning, or 2 x daily in the morning and evening.

Adult dosage range 500mg–2g daily.

Onset of effect Within 1 hour.

Duration of action 6–24 hours.

Diet advice An individualized diabetic diet must be maintained for the drug to be fully effective. Follow the advice of your doctor.

Storage Keep in original container at room temperature out of the reach of children. Protect from light.

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 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. If faintness, confusion, or headache occur, eat something sugary. Take emergency action if seizures or loss of consciousness occur.

POSSIBLE ADVERSE EFFECTS

Serious adverse effects are rare with tolbutamide. Symptoms such as dizziness, confusion, weakness, and sweating may indicate low blood sugar levels; if they occur, eat or drink something sugary and seek immediate medical help. Rarely, headache, ringing in the ears, and weight gain may occur; if they are severe, or if nausea, vomiting, or diarrhoea occur, discuss with your doctor. If you develop jaundice, fever, a rash, or easy bruising, stop taking the drug and contact your doctor immediately.

INTERACTIONS

General note A variety of drugs, including corticosteroids, oestrogens, diuretics, and rifampicin, may oppose the effect of tolbutamide and raise blood sugar levels. Others increase the risk of low blood sugar; these include sulphonamides, warfarin, chloramphenicol, aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs), antidepressants, cimetidine, and some antibiotics and antifungals.

Beta blockers may mask the signs of low blood sugar, especially non-cardioselective beta blockers such as propranolol.

SPECIAL PRECAUTIONS

Be sure to tell your doctor if:

· You have long-term liver or kidney problems.

· You are allergic to sulphonamides.

· You have thyroid problems.

· You have porphyria.

· You are taking other medicines.

Pregnancy Not prescribed. Insulin is usually substituted. May cause birth defects if taken in the first 3 months of pregnancy. Discuss with your doctor.

Breast-feeding The drug passes into the breast milk and may affect the baby. Discuss with your doctor.

Infants and children Not prescribed.

Over 60 Risk of low blood sugar. Reduced dose may therefore be necessary.

Driving and hazardous work Usually no problem. Avoid these activities if you have warning signs of low blood sugar.

Alcohol Keep consumption low. Alcohol may upset diabetic control and cause flushing, nausea, and vomiting.

Surgery and general anaesthetics Notify your doctor that you have diabetes before any surgery; insulin treatment may need to be substituted.

PROLONGED USE

No problems expected.

Monitoring Periodic monitoring of control of blood glucose levels is necessary.