But the results were not statistically better than improvement seen in 46 percent of patients given placebos.

A third group was given placebos.

The incidence of side effects among patients taking the Merck drug, at whatever dose, was similar to those seen among patients given placebos.

The drug was also associated with haemorrhages and a higher number of deaths in the phase III study, compared with patients given placebos.

However, the women given two acyclovir pills a day were not any less likely to become infected with the AIDS virus than women given placebos.

This compared to 41 percent of patients who got Zyprexa, known generically as olanzapine, and just 3 percent of the patients given placebos.