Dapsone and Trimethoprim interaction
Dapsone and Trimethoprim: the Dapsone prescribing label describes an interaction that usually calls for monitoring, a dose change, or spacing the doses.
Usually manageable with monitoring or a dose change. Tell your pharmacist you take both.
What the FDA labels say
From the Dapsone label · effective 2026-07-20
However, an earlier report 2 also by Lee et al, in 78 HIV infected patients with acute Pneumocystis carinii pneumonia, receiving dapsone, 100 mg/day and higher trimethoprim dose, 20 mg/kg/day, demonstrated that the serum levels of dapsone were increased by 40% and trimethoprim levels were increased by 48% when the drugs were administered concurrently.
A modest interaction has been reported for patients receiving 100 mg dapsone daily in combination with trimethoprim 5 mg/kg q6h.
On Day 7, trimethoprim levels averaged 18.4 ± 5.2 μg/mL in comparison to 12.4 ± 4.5 μg/mL for patients not receiving dapsone.
Thus, there is a mutual interaction between dapsone and trimethoprim in which each raises the level of the other about 1.5 times.
A crossover study 1 designed to assess the potential of a drug interaction between dapsone, 100 mg/day and trimethoprim, 200 mg every 12 hours, in eight asymptomatic HIV positive volunteers (average CD4 count 524 cells/mm 3 ) demonstrated that there was not a significant drug interaction between dapsone and trimethoprim.
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.