Several studies and reports have cast doubt on the effectiveness of AZT (zidovudine) as an anti AIDS drug, particularly in the early stages of the disease.

The latest study (New England Journal of Medicine 13 February 1992) showed that in a multicentre study of HIV positive patients with symptoms the drug delayed progression to AIDS but did not improve survival and was associated with more side effects. These included a severe drop in white cell count, severe anaemia, nausea, vomiting and diarrhoea.

These results clash with those of an unpublished study released by the Wellcome Foundation in mid February. That study, conducted among European and Australian HIV patients who did not yet evidence symptoms, showed that patients were benefiting significantly; consequently, the trial was stopped and all participants given the drug.

Wellcome came under recent fire on Dispatches, the Channel 4 television documentary, which took issue with the Burroughs Wellcome funded study, which led to "fast track" approval of the drug in 1987. According to an FDA internal report, which Dispatches got hold of, in the earlier study the subjects "unblinded themselves early" (that is, the participants knew who was getting the drug and who was getting the placebo) which could have led to bias.

Peter Duesberg of the department of molecular and cell biology at the University of California, Berkeley, has also pointed to studies showing that in one study 10 of 11 patients recovered cellular immunity on discontinuing AZT; another, that four patients with pneumonia developed severe bone marrow disease 12 weeks after starting on AZT, three of whom recovered as soon as they stopped the drug. (The Lancet, 29 February 1992)

Questions about AZT have led numerous AIDS groups in the States to campaign against the more widespread prescription of AZT to HIV positive patients not yet showing symptoms. Part of the reason for the debate is that the drug is apparently only effective for a short period of time; as a British Medical Journal editorial argues, the treatment ought to be reserved for when the risk of AIDS is high. The general feeling, highlighted in a New England Journal of Medicine (13 February) editorial is that more debate needs to be held on the subject before patients are blindly treated and that HIV infection therapy is only in its "infancy".