To the Editor.
—Recent studies have shown encouraging antiretroviral and immunological benefit from the combination of lamivudine and zidovudine.1-3 The cost of such combination therapy (with the possible addition of human immunodeficiency virus [HIV] protease inhibitors and nonnucleoside reverse transcriptase inhibitors) is considerable.A little publicized fact is that trimethoprim increases the bioavailability of lamivudine by approximately 40%.4 It is not stated in any of these trials precisely how many patients were receiving trimethoprim-sulfamethoxazole for Pneumocystis carinii pneumonia prophylaxis. Trials of combination therapy of trimethoprim and lamivudine may show that lower doses of lamivudine are effective with significant cost benefits.
Hudson M, Nash C. Effect of Trimethoprim on Lamivudine Bioavailability. JAMA. 1996;276(14):1140. doi:10.1001/jama.1996.03540140028020