Letter: The benefits of absorbing your drugs in your mouth

From Philip Welsby, Edinburgh, UK

You report that 64.9 per cent of drugs tested were broken down by at least one strain of gut bacteria (8 June, p 12). To minimise this, drugs shouldn't enter the gut directly. Some can be absorbed from the mouth, either under the tongue or through the buccal (cheek) mucosa. Many of these aren't, however, licensed to be given in this way.

This is a pity because oral absorption can be observed and is often equal to or greater than the assumed absorption from the gut. Also, drugs absorbed from the stomach and small intestine have to pass through the liver and may be inactivated there, while the route via the mouth membranes avoids this.

Drugs such as nitroglycerin for angina are given orally precisely because they provide rapid absorption and avoid the liver.

Against all considerations of logic or cost-effectiveness, drinkers often gulp down their drug, alcohol, gaining only a brief exposure to the taste. Liver inactivation of alcohol could reduce their exposure, which may or may not be desirable.