Antibiotic (Sulfonamide combination)
Last reviewed June 2026
Who is this for?
Sulfamethoxazole/Trimethoprim (commonly called Co-trimoxazole or Septrin) is a combination antibiotic that contains two medicines working together to kill bacteria by blocking two different steps they need to grow and multiply.
Inhibits bacterial dihydrofolate reductase (trimethoprim) and dihydropteroate synthase (sulfamethoxazole), blocking sequential steps in folate synthesis and preventing bacterial DNA replication and cell division.
Prescription Required
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Is Sulfamethoxazole; safe to take with another drug?
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For most infections, the usual adult dose is 2 regular-strength tablets (each containing 400mg sulfamethoxazole and 80mg trimethoprim) taken every 12 hours — that means one dose in the morning and one in the evening. Take with a full glass of water and drink plenty of water throughout the day to protect your kidneys. You can take it with or without food, but taking it with food can reduce stomach upset.
If you miss a dose, take it as soon as you remember. But if it is almost time for your next dose, skip the missed one and continue your normal schedule. Do not take a double dose to make up for the one you missed.
Important for antibiotics
Always complete the full course even if you feel better. Stopping early can cause the infection to return and become drug-resistant.
Always complete the full course of this antibiotic even if you start feeling better — stopping early can make the infection come back stronger and harder to treat. Drink plenty of water while taking this drug to protect your kidneys, especially in hot Nigerian weather. Buy only from licensed pharmacies — do not buy Co-trimoxazole from roadside vendors or open markets as fake and expired versions are common and can be dangerous.
Avoid taking with methotrexate (used for arthritis and cancer) as it can cause dangerous blood problems. Be careful if you are taking blood-thinning medicines like warfarin, as Co-trimoxazole can increase the risk of bleeding. Avoid alcohol while taking this drug as it may increase the chance of side effects and reduce how well the medicine works.
Check your specific combination
Is it safe to take Sulfamethoxazole; with your other drugs?
This drug is NOT safe during pregnancy, especially in the first three months and near delivery, and should be used with caution during breastfeeding — always consult your doctor before taking it if you are pregnant, planning to become pregnant, or breastfeeding.
Store in a cool, dry place away from direct sunlight and heat — Nigerian weather can be very hot, so avoid leaving it on window sills or inside hot cars. Keep the bottle or pack tightly closed to protect from humidity. Always keep out of reach of children. Suspension should be used within the period stated on the label after opening.
For information only — not medical advice. Always talk to a doctor or pharmacist before changing your medication.
Names this drug is sold under — especially in Nigerian and West African pharmacies
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Counterfeit Drug Warning
Fake drugs are a serious problem in Nigeria. Always buy from a registered pharmacy. If the packaging looks different from what is described above, do not use it.
Dispensing Sulfamethoxazole; Trimethoprim?
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