The efficacy of azathioprine in the treatment of multiple sclerosis was assessed by meta-analysis of the results of all published blind, randomised, controlled trials. 793 patients were enrolled in 5 double-blind and 2 single-blind studies. After 1 year of treatment, the increase in Kurtzke disability status score was no different in treated and control groups, but at 2 years there was a small difference (-0.22; 95% confidence interval [CI] -0.43, 0.003) in favour of azathioprine treatment; this difference was sustained, but not increased, after 3 years. The probability of freedom from any relapse during 1, 2, and 3 years' treatment was significantly greater in the azathioprine-treated group (relative odds over 3 years 1.97; 95% Cl 1.27, 3.04), but it is debatable whether the slight clinical benefits of azathioprine outweigh its side-effects.

The dietary factors believed to be linked with the incidence of coronary heart disease are reviewed in the light of evidence with regard to their functional role, either in protection or in promotion. Detailed analysis of the evidence shows that the relations are more complex than the current lipid hypothesis suggests. It is proposed that, in particular, the polyunsaturated/saturated ratio as a measure of the propensity of the diet to influence the incidence of coronary heart disease should be replaced by indices of atherogenicity and thrombogenicity.

To assess the effect of selective decontamination of the digestive tract on respiratory tract infections and survival of patients treated in an intensive care unit, we carried out a meta-analysis of clinical studies comparing patients treated with selective decontamination with untreated controls. From eleven trials (1489 patients), differences between observed and expected respiratory tract infections and mortality were compared, and odds ratios (ORs) calculated. Analysis was done according to study design. With respect to the risk for respiratory tract infections, the studies with historical controls and the randomised trials showed a protective effect of selective decontamination. Historical control studies yielded an OR of 0.21 (95% confidence limits [CL] 0.15 to 0.29, p less than 0.05) and randomised trials an OR of 0.12 (95% CL 0.08 to 0.19, p less than 0.05). By contrast, the mortality benefit was less clear. Studies with historical controls and randomised trials showed that mortality was not significantly different between treatment and control patients. The evidence from these studies is at best consistent with a very limited effect of selective decontamination of the digestive tract on survival of patients in the intensive care unit, despite a clear preventive effect on the occurrence of respiratory tract infections.

The World Health Organisation Model List of Essential Drugs is an attempt to provide guidelines for selection of essential pharmaceuticals. Analysis of the six lists produced between 1977 and 1990 shows an increase in the number of items from 205 to 268. 120 drugs have been added and 57 deleted; however, only 16 of the additional drugs can be considered new clinical entities or to have new indications. The original purpose of the essential drug list was to itemise the minimum number of essential drugs. Many additions were due to a change in perception about the usefulness of a particular drug, not scientific advances. Nevertheless, the list remains a useful guide for countries selecting their own national lists.

The origin of the increased frequency of side-effects to co-trimoxazole in HIV-positive patients is unknown. Data on plasma concentrations of the parent compounds are inconclusive. Evidence points to the hydroxylamine derivatives of sulphamethoxazole as the reactive metabolites that cause adverse reactions to co-trimoxazole. HIV-positive individuals have a systemic glutathione deficiency, and therefore a reduced capacity to scavenge such metabolites. This process would lead to an increased exposure to toxic intermediates and would explain the high frequency of adverse reactions to co-trimoxazole in these patients.