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October 9, 1996

Effect of Trimethoprim on Lamivudine Bioavailability

Author Affiliations

Royal Hallamshire Hospital Sheffield, England

JAMA. 1996;276(14):1140. doi:10.1001/jama.1996.03540140028020

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.