Precose

Precose contains acarbose, which competitively blocks the alpha-glucosidase enzymes lining the small intestine, especially sucrase. Starch and table sugar are then broken down into absorbable glucose more slowly, so the rise in blood sugar after a meal is flatter and fluctuations through the day are smoothed out. Only 1–2% of the drug is absorbed, and it does not stimulate the pancreas to release insulin. The UK SmPC licenses acarbose for type 2 diabetes that is not controlled well enough by diet alone, or by diet with metformin and/or a sulphonylurea.

You can select 30, 60, 90, 120, 180 or 360 of the 25 mg tablets; for 50 mg, the choice stops at 180 (30, 60, 90, 120 or 180). UK-licensed acarbose is made as 50 mg and 100 mg tablets, so the 25 mg strength is not a UK presentation and is supplied as an imported generic. Lower strengths can be useful for a slow start, which is often the best way to keep wind and bloating manageable. Packaging may differ from UK packs.

There is no fixed regimen, because enzyme activity varies widely between people. The SmPC suggests starting with 50 mg three times a day, or building up from once or twice daily to reduce gut symptoms. If control is not good enough after six to eight weeks, the dose may rise to 100 mg three times daily, and occasionally to a maximum of 200 mg three times daily. Each tablet is swallowed whole with a little liquid just before a meal, or chewed with the first mouthful of food. If wind or diarrhoea persists despite following a diabetic diet, the dose should not be increased. Children and teenagers should not use it, as there is no safety evidence for that age group.

Precose is a trade name not used on UK packs; in the UK the medicine is sold as generic acarbose tablets, for example from Glenmark Pharmaceuticals, and it is a prescription-only medicine (POM). Diabetes treatment is tailored to blood glucose and HbA1c results, and the prescriber decides whether acarbose fits alongside other glucose-lowering medicines. Because it works only on carbohydrate in the gut, it has little effect if a meal is skipped, so a dose is normally left out when no meal is eaten.

The SmPC contraindicates it in pregnancy and breastfeeding, inflammatory bowel disease, colonic ulceration, partial bowel obstruction or a tendency to it, chronic intestinal disease with marked problems of digestion or absorption, conditions that could worsen with increased gas (such as large hernias), any degree of liver impairment, and kidney impairment with creatinine clearance below 25 ml/min. Charcoal and digestive enzyme products containing amylase or pancreatin weaken its effect and should not be taken with it. Colestyramine and oral neomycin can strengthen its action and gut side effects.

Flatulence, bloating, abdominal pain and diarrhoea are very frequent, because undigested carbohydrate is fermented in the colon; sugary foods make this worse. On its own acarbose does not cause hypoglycaemia, but combined with insulin, metformin or a sulphonylurea blood sugar can fall too low. A hypo during treatment must be treated with glucose (dextrose tablets or gel), not ordinary sugar, because Precose delays the breakdown of sucrose. Severe stomach pain, persistent vomiting or yellowing of the skin needs prompt medical attention while taking Precose.