What it is used for
- Some urinary tract infections
- Certain chest and ear infections
- Some skin infections
- Prevention and treatment of certain lung infections in people with weakened immune systems
- Some travel-related gut infections
How it works
This medicine combines two antibiotics, trimethoprim and sulfamethoxazole, that together block steps bacteria need to make folate, a substance essential for their growth. Blocking two steps makes the combination more effective against many bacteria.
How it is taken
Comes as tablets, a liquid (oral suspension) and an injection in hospital. Take it exactly as your doctor or pharmacist directs and follow the label. Drink plenty of fluids while taking it. Complete the full course as advised.
No doses here on purpose. The right strength and schedule depend on you — only a doctor or pharmacist should set them. Always follow your prescription and the label.
Common side effects
- Nausea
- Vomiting
- Loss of appetite
- Diarrhoea
- Rash
- Headache
Serious effects — get help
- Severe skin reactions with blistering, peeling or sores in the mouth (seek urgent care)
- Severe allergic reaction with swelling or breathing difficulty
- High potassium signs such as muscle weakness or an irregular heartbeat
- Unusual tiredness, pale skin, easy bruising or sore throat (possible blood problem)
- Yellowing of the skin or eyes
- Severe, persistent or bloody diarrhoea
If a reaction is severe — for example trouble breathing, swelling of the face or throat, or collapse — go to the nearest emergency room now or call your local emergency number. Do not wait for an online consultation.
Interactions to watch
- Blood thinners such as warfarin
- Methotrexate
- Some blood pressure and heart medicines (ACE inhibitors, ARBs) and potassium supplements
- Certain diabetes medicines
- Some water tablets (diuretics)
- Phenytoin
Who should take care
- Tell your clinician about any sulfa (sulfonamide) allergy
- Usually avoided in late pregnancy and in young babies
- Tell your clinician if you have kidney or liver problems or a known G6PD deficiency
- Drink plenty of fluids
- Report any new rash promptly, as serious skin reactions are possible