Does Sulfamethoxazole And Trimethoprim Interact with Dapsone?
Sulfamethoxazole And Trimethoprim and Dapsone have a moderate drug interaction according to U.S. FDA drug labeling data. TMP/SMX increases systemic levels of dapsone and its metabolites (AUC increased ~40% for dapsone, ~20% for N-acetyldapsone, >100% for dapsone hydroxylamine). Monitor for increased dapsone exposure and potential toxicity. The mechanism involves inhibition of dapsone metabolism. Patients taking both medications should consult their healthcare provider before starting, stopping, or changing the dosage of either drug. This information is based on official FDA drug labeling sourced from OpenFDA and the NIH National Library of Medicine.
- Severity
- Moderate
- Sulfamethoxazole And Trimethoprim Class
- Sulfonamide Antimicrobial
- Dapsone Class
- Sulfone
- Management
- Monitor for effects
- Data Source
- U.S. FDA via OpenFDA
How This Interaction Works
The interaction between Sulfamethoxazole And Trimethoprim and Dapsone occurs because inhibition of dapsone metabolism. Clinically, this means tmp/smx increases systemic levels of dapsone and its metabolites (auc increased ~40% for dapsone, ~20% for n-acetyldapsone, >100% for dapsone hydroxylamine). monitor for increased dapsone exposure and potential toxicity. This is classified as a moderate interaction. While it may not require stopping either medication, your healthcare provider should be aware you are taking both so they can monitor for potential effects and adjust treatment if necessary.
What To Tell Your Doctor or Pharmacist
If you are taking Sulfamethoxazole And Trimethoprim and your doctor is considering prescribing Dapsone (or vice versa), make sure to:
- Inform your doctor and pharmacist of all current medications, including over-the-counter drugs and supplements
- Ask whether the benefits of combining these medications outweigh the risks for your specific situation
- Ask what symptoms to watch for that would indicate the interaction is causing problems
- Ask whether any dosage adjustments are needed
- Never stop or change either medication without first consulting your healthcare provider