The drugs, their dosage and approximate duration of action are shown in Table 8.3. Start with a small dose which can be increased every few days according to blood glucose concentrations. Increase chlorpropamide at weekly intervals or longer because of its long half-life.


Hypoglycaemia may occur. All sulphonylureas can cause allergic rashes, gastrointestinal disturbances (usually mild) such as anorexia, nausea, and vomiting, and, rarely, reduction in platelets, white cells, or aplastic anaemia. They can also cause flushing with alcohol although this is particularly pronounced with chlorpropamide. Weight gain may be a problem in some patients. Cholestatic jaundice (usually reversible) may occur with chlorpropamide and hepatic dysfunction may be caused by some sulphonylureas. Chlorpropamide also has an anti-diuretic hormone-like action and hyponatraemia is not uncommon, especially in people taking diuretics.

Contraindications and cautions

Diabetic ketoacidosis, pregnancy, and breast-feeding. Caution in renal or hepatic dysfunction. Various drug interactions with sulphonylureas are outlined in Table 8.5.

Which sulphonylurea?

The one you are used to. Chlorpropamide is taken once daily and can provide gentle action because it is so long-acting. However, it can cause prolonged hypoglycaemia and may be dangerous in the elderly. Glibenclamide is widely used. It is much longer-acting than people think. The glucose-lowering effect may last over 24 hours, especially in renal impairment. Glibenclamide enters the pancreatic islets. It may cause profound

Table 8.3 Sulphonylureas


Dosage range per 24 hrs

Dosage frequency


50-500 mg

once a day


40-320 mg

once/twice a day

Gliclazide as Diamicron 30 MR

30-120 mg

once a day



once a day


2.5-20 mg

once/twice a day


15-180 mg

one to three times a day


500-2000 mg

one to three times a day

Table 8.4 Information for patients on sulphonylurea tablets

1. Your diabetes tablets are called

They belong to a family of medicines called sulphonylureas. Take mg ( tablet(s)) before breakfast;

Take mg ( tablet(s)) before main evening meal.

2. The tablets will help your diabetic diet to control your blood glucose level.

3. The tablets will work only if you take them regularly as prescribed!

4. If you are too unwell to take your tablets for any reason contact your doctor or diabetes nurse immediately.

5. If you cannot eat, or are vomiting, do not take your tablets but contact your doctor or diabetes nurse immediately.

6. Side-effects are usually mild and infrequent and include stomach or bowel upset and headache. Flushing may occur with alcohol. Allergic rashes, jaundice, and blood problems occur rarely.

7. These tablets work by reducing the blood glucose. Sometimes the blood glucose may fall too low (i.e. below 4 mmol/l). This is called hypoglycaemia and may happen if you are taking too big a dose, eat too little, or exercise more than you expect. If you feel muddled, slow-thinking, tingly, unduly emotional or cross, sweaty, shaky or notice your heart thumping fast, eat some glucose, then have a big snack. Contact your doctor or diabetes nurse. You may need to reduce your dose of tablets.

8. Over the years your diabetes may slowly progress. As your pancreas 'wears out' the tablets may become less effective. Some people may need insulin injections eventually. You may also need insulin temporarily if you are ill or have an operation.

9. Although your diabetes does not need insulin treatment at present you must take just as much care of yourself in general as someone on insulin injections. There is no such thing as mild diabetes. Your doctor will help you to stay well.

10. Always carry a diabetes card and some glucose with you.

This table may be photocopied for use by patients only. © 2002 Dr Rowan Hillson. From Practical diabetes care, Oxford University Press, 2002.

Table 8.5 Drug interactions with sulphonylureas

Lower blood glucose

Raise blood glucose


Alcohol (+flushing)


Chloramphenicol Co-trimoxazole Miconazole Sulphonamides



Beta blockers (+reduce hypo warning)

Diazoxide Loop diuretics (Nifedipine) Thiazides




H2 antagonists



Corticosteroids Contraceptives

Phenylbutazone NSAIDs

Sulphinpyrazone Azapropazone


Phenobarbitone Tricyclics (+postural hypotension)

hypoglycaemia on as small a dose as 2.5 mg and can also cause prolonged hypoglycaemia. Glibenclamide is the commonest cause of hypoglycaemia due to oral agents. One in three patients taking glibenclamide experience hypoglycaemia. Tolbutamide and glipizide are both short-acting and can be linked to meals to allow some patients flexibility in dosage—small meals, small dose; big meal, big dose. Gliclazide reduces platelet stickiness which could reduce the risk of vascular complications, but glucose-lowering itself can have effects on platelets. Gliclazide also seems less likely to produce sudden hypogly-caemia than glibenclamide; it is becoming increasingly popular but costs more.

Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

Get My Free Ebook

Post a comment