Acarbose

Some of the views expressed in the following notes on newly approved products should be regarded as preliminary, as there may have been limited published data at the time of publication, and little experience in Australia of their safety or efficacy. However, the Editorial Executive Committee believes that comments made in good faith at an early stage may still be of value. Before new drugs are prescribed, the Committee believes it is important that more detailed information is obtained from the manufacturer's approved product information, a drug information centre or some other appropriate source.

Glucobay (Bayer)

50 mg and 100 mg tablets

Indication: diabetes mellitus

At present, non-insulin dependent diabetes can be managed with non-drug treatment, a biguanide or a sulfonylurea. If the blood glucose is not well controlled by these treatments, the patient can now be offered acarbose. Although acarbose has been approved for use in any patient who does not respond to a diet, it will be most useful as an addition to other oral hypoglycaemic drugs or when they are contraindicated or not tolerated.

Acarbose is a saccharide which competes with oligosaccharides for the binding sites on the intestinal glucosidase enzymes such as sucrase and maltase. As acarbose has a high affinity for the binding sites, it acts as a reversible enzyme inhibitor. This results in delayed absorption of dietary carbohydrate and therefore a reduced postprandial rise in blood glucose.

The tablets are taken whole just before a meal or chewed with the first few mouthfuls of food. Acarbose acts in the small intestine and only 1-2% is absorbed. Half of each dose is excreted in the faeces, but there are many metabolites which may be absorbed. (Approximately 35% of a radio-labelled dose will appear in the urine.) Patients with severe renal disease (creatinine clearance <25 mL/minute) should not take acarbose.

In clinical trials, acarbose reduced concentrations of glycosylated haemoglobin (HbA1c) significantly more than placebo. However, in one study of 40 patients who had not responded to diet alone, the difference was not significant.¹ Acarbose has also been studied as an addition to treatment with a sulfonylurea. This can lead to further reductions in HbA1c. Although these additional reductions are statistically significant, they are not large. For example, in one study, the mean effect was to reduce HbA1c by 0.54%. Although acarbose has been available overseas for a few years, it is not yet clear if the drug leads to reduced complications or avoids the need to start insulin.

The potential benefits of acarbose are not without the risk of adverse effects. The passage of undigested dietary carbohydrate into the small intestine results in flatulence, diarrhoea and abdominal pain in the majority of patients. These symptoms are dose dependent and may improve with time. If the diarrhoea persists, the dose may have to be reduced or stopped. Acarbose should not be prescribed to patients with chronic intestinal problems such as inflammatory bowel disease or malabsorption.

Acarbose does not induce hypoglycaemia unless it is being used with other hypoglycaemic drugs. Patients who develop acute hypoglycaemia should be given glucose as acarbose will slow the response to sucrose (cane sugar).

Higher doses of acarbose can increase liver transaminases. Patients taking more than 600 mg daily should have monthly liver function tests.