About trimethoprim bp sulphamethoxazole bp
Sulfonamide and dihydrofolate reductase inhibitor combination
Used for
- Urinary tract infections
- Certain chest infections, including Pneumocystis pneumonia
- Some ear infections and shigellosis
Usual adult dose
Common infections: one tablet twice daily; dose and duration depend on infection and kidney function.
Usual dose in children
For selected infections: 6 mg/kg trimethoprim and 30 mg/kg sulfamethoxazole daily, divided twice daily; clinician-directed.
Common side effects
- Nausea, vomiting, or diarrhoea
- Skin rash or itching
- Raised potassium or changes in blood counts
- Rare severe skin reactions
Important warnings
- Avoid with sulfonamide or trimethoprim allergy.
- Seek urgent care for blistering rash, facial swelling, or breathing difficulty.
- Extra caution with kidney or liver disease, folate deficiency, or blood disorders.
- Not suitable for some newborns; dosing may need adjustment in kidney impairment.
Pregnancy
Use only when clearly needed; pregnancy-specific risks and alternatives should be discussed with a clinician.
Breastfeeding
Small amounts pass into breast milk. Avoid or seek specialist advice with premature, jaundiced, or ill newborns.
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 It may be incomplete or out of date.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.