To the Editor.
—Dapsone and primaquine phosphate are commonly used in the prophylaxis and treatment of Pneumocystis carinii pneumonia (PCP) in patients with human immunodeficiency virus (HIV) infection. A 42-year-old man with AIDS presented with a 2-week history of fever, chills, shortness of breath, and nonproductive cough. The chest x-ray film revealed a diffuse fine infiltrate suggestive of PCP. The diagnosis was later confirmed with bronchoalveolar lavage. On admission, an arterial blood gas analysis revealed a pH of 7.43, Pco2 of 35.2 mm Hg, Po2 of 82.5 mm Hg, and arterial blood oxygen saturation (sAO2) of 89.2% on room air. The CD4+ cell count was 0.018X109/L (18/μL). The patient was allergic to sulfa drugs and had been taking oral dapsone (100 mg daily) as PCP prophylaxis for the past 5 years. He was started on intravenous clindamycin (900 mg, 3 times daily) and primaquine