Sulfamethoxazole/trimethoprim (SMX/TMP) can interact with several medications. Careful monitoring is necessary if you’re taking other drugs.
Increased Risk of Side Effects
- Warfarin: SMX/TMP increases the risk of bleeding by potentiating warfarin’s anticoagulant effect. Closely monitor INR levels. Methotrexate: SMX/TMP can significantly elevate methotrexate levels, increasing toxicity. Careful dose adjustment or avoidance of SMX/TMP may be required. Phenytoin: SMX/TMP can displace phenytoin from protein-binding sites, leading to elevated phenytoin levels and potential toxicity. Monitor serum phenytoin concentrations.
These interactions can manifest as increased bleeding (with warfarin), bone marrow suppression (with methotrexate), or neurological symptoms (with phenytoin).
Reduced Effectiveness
Certain diuretics: Some diuretics (like loop diuretics) can reduce the effectiveness of SMX/TMP by altering urinary pH. Your doctor may need to adjust the SMX/TMP dosage. Antacids: Antacids containing aluminum or magnesium can reduce SMX/TMP absorption. Separate administration by at least 2 hours is recommended.
Other Potential Interactions
- Cyclosporine: SMX/TMP may increase cyclosporine levels, potentially increasing the risk of nephrotoxicity. Monitor cyclosporine levels and renal function. Probenecid: Probenecid inhibits the renal excretion of SMX, increasing its concentration and risk of side effects. This interaction requires careful management.
Always inform your doctor or pharmacist of all medications, including over-the-counter drugs and herbal supplements, you are taking before starting SMX/TMP. This allows for proper monitoring and risk mitigation.
Note:
This information is not exhaustive. Consult your healthcare provider for personalized advice regarding potential drug interactions with SMX/TMP.
