Medicine peddles two types of drugs to help us lose weight: amphetamines and drugs which act on the central nervous system as appetite suppressants. Many are potentially addictive, and cause headaches, insomnia and hallucinations. And once again there is no evidence of long-term weight reduction.

Dexfenfluramine, an amphetamine and appetite suppressant, is licensed for use in the UK but restricted to a maximum prescription period of three months due to its particularly unpleasant side effects. These include gastrointestinal complaints, especially diarrhea, drowsiness, dizziness, lethargy, dry mouth, headache, sleep disturbances, visual disorders, low blood pressure, urinary frequency, impotence and loss of libido. Rashes, blood disorders and pulmonary (lung) hypertension have also been reported. A particularly worrying side effect is depression, brought on by sudden withdrawal of the drug (The Lancet, June 1, 1991).So far, there's been at least one fatal case of pulmonary hypertension during long-term dexfenfluramine therapy, although a direct link with the drug hadn't been established. (Drugs, 1992; 43 (5):713-33).

Even more alarmingly, last year a study using animals indicated that dexfenfluramine causes persistent and possibly permanent brain damage. The study stated that "physicians and patients alike need to be aware of dexfenfluramine's toxic potential toward brain serotonin neurons." (Journal of Pharmacology and Experimental Therapeutics, 1994; 269:792-8). Furthermore, dexfenfluramine has never been directly compared with non-drug methods of weight control like behaviour modification or exercise programmes (Drugs, 1992; 43(5): 713-33)

Other potential drugs being considered are antidepressants. At the dose required to achieve "significant" weight-loss, sibutramine can cause insomnia, irritability, rapid heartbeat and occasionally high blood pressure and thrombocytopenia (reduction of blood-clotting platelets) (Clinical Pharmacology and Therapeutics, September 1991).