Prophylaxis for toxoplasma
encephalitis was performed with
pyrimethamine alone (50 mg daily) in 56 patients with advanced
HIV infection. Thirty-eight patients were at high risk for toxoplasma
encephalitis (CD4+ counts < or = 200/microliter, and presence of serum
IgG antibodies to Toxoplasma gondii). The overall treatment period was 697 months (mean 12.5 +/- 12.1). During prophylaxis, only one patient developed toxoplasma
encephalitis, four patients discontinued treatment due to adverse reactions. Steady state
pyrimethamine plasma concentrations were measured by gas chromatography. Mean plasma level was 1,887 +/- 1,161 ng/ml, during liver
enzyme-inducing comedication plasma levels were significantly (p = 0.0001) reduced (1,488 +/- 884 ng/ml versus 1,978 +/- 1,196 ng/ml without comedication). All patients received a
folinic acid supplement of 7.5 mg daily. Serum
folate levels ranged from 5.7-105 (43.7 +/- 29.2) nmol/l; severe hematological side effects did not occur.