Dapsone, trimethoprim, and sulfamethoxazole plasma levels during treatment of Pneumocystis pneumonia in patients with the acquired immunodeficiency syndrome (AIDS). Evidence of drug interactions.
Author(s): Lee BL, Medina I, Benowitz NL, Jacob P 3rd, Wofsy CB, Mills J 5th
Affiliation(s): San Francisco General Hospital Medical Center, California.
Publication date & source: 1989-04-15, Ann Intern Med., 110(8):606-11.
Publication type: Clinical Trial; Randomized Controlled Trial
STUDY OBJECTIVE: To examine the interaction between dapsone and trimethoprim in patients with the acquired immunodeficiency syndrome (AIDS). DESIGN: Measurement of drug levels as part of an open study of dapsone alone and randomized, double-blind comparison of trimethoprim-dapsone with trimethoprim-sulfamethoxazole in treating Pneumocystis carinii pneumonia in patients with AIDS. SETTING: County hospital and AIDS clinic. PATIENTS: Eighteen patients treated with dapsone alone, 30 with trimethoprim-dapsone, and 30 with trimethoprim-sulfamethoxazole. INTERVENTION: Dapsone, 100 mg/d; trimethoprim, 20 mg/kg body weight per day, and sulfamethoxazole, 100 mg/kg.d; administered for 21 days. MEASUREMENTS AND MAIN RESULTS: Concentrations of dapsone were 40% higher in patients treated with trimethoprim-dapsone than in those treated with dapsone alone (2.1 compared with 1.5 micrograms/mL; P less than 0.05). Trimethoprimdapsone-treated patients had fewer treatment failures but more side effects and treatment terminations due to toxicity than those treated with dapsone alone. The concentration of trimethoprim was 48.4% higher in patients treated with trimethoprim-dapsone than in those treated with trimethoprim-sulfamethoxazole, (18.4 compared with 12.4 micrograms/mL; P less than 0.05). Discontinuation of therapy due to toxicity was commoner in the trimethoprim-sulfamethoxazole group (57% compared with 30%). CONCLUSIONS: A bidirectional drug interaction exists between dapsone and trimethoprim, resulting in higher concentrations of each in the presence of the other.
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