Anti-toxoplasma activities of antiretroviral drugs and interactions with pyrimethamine and sulfadiazine in vitro.

The anti-Toxoplasma activities of nine antiretroviral drugs were examined in vitro. Nucleoside analogs had no effect on parasite growth, whereas ritonavir and nelfinavir were inhibitory for Toxoplasma, with 50% inhibitory concentrations of 5.4 and 4.0 microg/ml, respectively. None of the antiviral drugs affected the anti-Toxoplasma activity of pyrimethamine or sulfadiazine.