HEALTH / Common Remedies: Drugs to prevent vomiting

NAUSEA and vomiting are horrid sensations, but doctors may sometimes seem to give them little attention. The medical approach is first to establish the cause. If the underlying condition is some disease of the stomach, liver, or gall-bladder, then the vomiting may be given a low priority while treatment is aimed at the main target. When vomiting is due to food poisoning all that may be offered is advice to drink plenty of fluids and reassurance that symptoms rarely last more than 24 hours. Women who vomit early in pregnancy are commonly told that this is normal and transitory.

Fortunately these attitudes do not extend to other causes of vomiting such as motion sickness, diseases of the inner ear such as Meniere's syndrome, migraine, or the side-effects of cancer treatment.

Vomiting is controlled by a nerve centre in the medulla, the narrow part of the brain at the back of the skull that leads down to the spinal cord. The reflex may be triggered by a nearby centre sensitive to drugs and chemicals, by inputs from the stomach and other digestive organs, by the balance organs of the inner ear, and by emotion and fear. The vomiting centre is close to other nerve centres that control breathing, salivation, and blood pressure, and someone who is about to vomit is usually pale, sweaty, salivating and dizzy. If vomiting is to be suppressed, this part of the brain has to be sedated, and drugs which do this commonly affect other brain functions as well.

Research on troops preparing for the D-Day landings in the Second World War showed that the most effective treatment for sea sickness was hyoscine, a natural plant substance. Fifty years of research by the pharmaceutical industry has failed to develop a synthetic drug that is clearly better than hyoscine; what it has done is find an ingenious way of giving the drug. Someone who wants to avoid travel sickness nowadays may fix a sticky little patch containing the drug to the skin behind the ear, where it will deliver a small, steady dose into the bloodstream.

The main alternatives to hyoscine for motion sickness and many other types of vomiting are antihistamine drugs such as cinnarizine and cyclizine. Whatever the choice, some side-effects are inevitable - drowsiness and dry mouth and often blurred vision; sometimes emptying the bladder may become difficult.

The most difficult category of vomiting to control is that caused by anti-cancer drugs. With some of the most effective drugs such as cisplatin, the sickness may be extremely distressing. Phenothiazine drugs such as prochlorperazine are powerful anti-emetics and also relieve anxiety. Metoclopramide and related drugs act both on the brain and the stomach. Ondansetron, recently available, has proved very effective in treating vomiting caused by drugs or by radiotherapy.

Several treatments from alternative medicine have been shown to suppress vomiting. These include acupressure (by bands worn round the wrist), acupuncture, ground ginger, and cannabis derivatives. Use of these and the large number of drugs commonly prescribed indicate that none is completely satisfactory. Indeed, many people prefer to put up with their symptoms rather than the side-effects of drugs.