About sulfamethoxazole + trimethoprim
Sulfonamide and dihydrofolate reductase inhibitor antibiotic
Used for
- Treats certain bacterial infections, including urinary, respiratory, and ear infections.
- Treats or prevents Pneumocystis pneumonia in people at risk.
Usual adult dose
Commonly 800/160 mg by mouth every 12 hours for many infections; dose varies by infection and kidney function.
Usual dose in children
For children over 2 months, commonly 8 mg/kg trimethoprim plus 40 mg/kg sulfamethoxazole daily, split every 12 hours; dose depends on infection.
Common side effects
- Nausea, vomiting, or loss of appetite
- Rash, itching, or increased sun sensitivity
- Diarrhoea
- Rarely, serious blood disorders or severe skin reactions
Important warnings
- Not for infants younger than 2 months.
- Avoid with sulfonamide or trimethoprim allergy; seek urgent care for blistering rash or facial swelling.
- Can cause high potassium, kidney problems, or blood disorders; monitoring may be needed.
- Maintain adequate fluids; doses may need adjustment with kidney impairment.
Pregnancy
Use only when clearly needed after clinician assessment; avoid near term where possible because of newborn jaundice risk.
Breastfeeding
Usually compatible for healthy, full-term infants, but avoid or seek advice for premature, jaundiced, ill, or glucose-6-phosphate dehydrogenase-deficient infants.
Interactions
- Warfarin: may increase bleeding risk.
- Methotrexate: may increase toxicity.
- ACE inhibitors or spironolactone: may increase potassium.
- Phenytoin: may increase phenytoin levels.
AI-generated from general medical knowledge, not from this product's official leaflet. It may be incomplete or out of date. Not medical advice — ask a pharmacist or doctor before making any decision.