Sulfamethoxazole/trimethoprim can cause several side effects. The most common are nausea, vomiting, diarrhea, and stomach upset. These usually resolve on their own, but if they persist or worsen, consult your doctor.
Common Side Effects
- Nausea Vomiting Diarrhea Abdominal pain Rash Headache Fatigue
Less common, but more serious, side effects include allergic reactions like Stevens-Johnson syndrome (a severe skin reaction) or toxic epidermal necrolysis (TEN). Seek immediate medical attention if you experience a severe rash, blistering, peeling skin, or mouth sores. Blood disorders, such as a decrease in white blood cells, are also possible.
Less Common, but Serious Side Effects
- Severe allergic reactions (Stevens-Johnson syndrome, Toxic Epidermal Necrolysis) Blood disorders (leukopenia, thrombocytopenia) Liver damage Kidney problems
This medication can interact with other drugs. Specifically, it can increase the effects of warfarin (a blood thinner), potentially increasing bleeding risk. It may also interact with methotrexate (a cancer drug and rheumatoid arthritis medication), increasing its toxicity. Always inform your doctor about all medications, vitamins, and herbal supplements you are taking before starting sulfamethoxazole/trimethoprim.
Drug Interactions
Warfarin (increased bleeding risk) Methotrexate (increased toxicity) Phenytoin (altered levels) Oral contraceptives (decreased effectiveness)
This information is not exhaustive. For a complete list of potential side effects and drug interactions, consult your physician or pharmacist or refer to the medication’s package insert. They can provide personalized advice based on your individual health history and other medications you may be taking.
