Chronic effects of azidothymidine and acyclovir on pregnant rats.

1. The antiviral effect of azidothymidine (AZT) can be potentiated by acyclovir (ACV), and this drug association has been used in the management of HIV-infected patients. In the present study we examined the effects of such an association on rat pregnancy. 2. AZT (60 mg/kg b.w.) and ACV (60 mg/kg b.w.) were given to groups of pregnant rats once a day from the 1st to the 20th day of gestation. 3. Maternal body weight gain was severely affected by ACV; this effect was attenuated in rats treated with AZT+ACV and was virtually absent with AZT alone. 4. The abortive action of ACV was markedly diminished in the group treated with the association AZT+ACV. 5. The deleterious effects of ACV on rat pregnancy are presumably due to its extraplacental actions, and these are, at least in part, counteracted by concomitant treatment with AZT.