LEVELS OF DAPSONE AND PYRIMETHAMINE IN SERUM DURING ONCE-WEEKLY DOSING FOR PROPHYLAXIS OF PNEUMOCYSTIS-CARINII PNEUMONIA AND TOXOPLASMIC ENCEPHALITIS

Concentrations of dapsone, monoacetyldapsone, and pyrimethamine were d etermined in 36 serum samples from human immunodeficiency virus-infect ed patients on prophylaxis with once-weekly administration of dapsone- pyrimethamine (200 mg of dapsone-75 mg of pyrimethamine). During day 1 after ingestion, median levels of 1,038 ng of dapsone per mi and 356 ng of pyrimethamine per mi were found. During days 6 to 7, the dapsone level fell to < 20 ng/ml in five of nine serum samples, but the pyrim ethamine level remained elevated (125 ng/ml). Concurrent, but separate ly ingested, didanosine administration did not seem to decrease the dr ug concentrations.