Co‑trimoxazole in the UK – What You Need to Know

If you’ve been told to take co‑trimoxazole (also called trimethoprim / sulfamethoxazole), you probably have questions about how it works, the right dose and where to get it safely. This guide breaks down everything a UK patient needs – no jargon, just practical info.

How co‑trimoxazole is used

Co‑trimoxazole is a combo antibiotic that fights bacterial infections such as urinary tract infections (UTIs), bronchitis, and certain skin conditions. It works by stopping bacteria from making folic acid, which they need to grow. Because it hits two points in the bacteria’s pathway, resistance is less common than with single‑drug antibiotics.

Typical UK dosing

The standard adult dose for most infections is one double strength tablet (800 mg trimethoprim + 160 mg sulfamethoxazole) twice a day, taken with a full glass of water. For children, the dose is calculated by weight – usually 6‑12 mg/kg of trimethoprim per day, split into two doses. Always follow your GP’s instructions; stopping early can let infection return.

Take the tablets at regular intervals (e.g., 8 am and 8 pm) to keep blood levels steady. If you miss a dose, take it as soon as you remember unless it’s almost time for the next one – then skip the missed one. Never double‑dose.

Common side effects and when to seek help

Most people tolerate co‑trimoxazole well, but expect mild nausea, loss of appetite or a rash in about 5–10 % of users. If you develop a severe skin reaction (blistering, peeling), fever, sore throat or yellow eyes, stop the medicine and call your GP right away – these could be signs of a serious allergic response.

Rarely, the drug can affect blood counts or kidney function. Your doctor may order a blood test after two weeks if you’re on a long course. Watch for dark urine, unusual bruising or persistent fatigue and report it promptly.

Getting a legal prescription in the UK

You need an NHS or private prescription to obtain co‑trimoxazole. If your GP thinks the drug is right for you, they’ll issue a paper script or send an electronic one to a registered pharmacy. Online pharmacies that are CQC‑registered and display the MHRA logo can dispense it legally – just upload your prescription or have the doctor send it directly.

Avoid “black‑market” sites that promise cheap antibiotics without a script. Those products may be counterfeit, sub‑potent or even harmful. Stick to reputable UK pharmacies like Boots, Lloyds, or NHS‑approved online services.

Cost and insurance coverage

The price of co‑trimoxazole varies. Under the NHS prescription exemption, many patients pay a flat £9.35 per item (or get it free if they qualify for prepayment certificates). Private purchases typically range from £4 to £8 per double‑strength pack, depending on the pharmacy and any discounts.

If you have private medical insurance, check whether antibiotics are covered – some plans only reimburse after a GP referral. Always keep your receipt; you might claim back under certain health cash plans.

Tips for safe use

• Take the full course even if symptoms improve.
• Avoid alcohol while on co‑trimoxazole – it can increase nausea.
• Stay hydrated; plenty of water helps kidneys clear the drug.
• If you’re pregnant or breastfeeding, discuss risks with your doctor. The drug is generally safe in the second trimester but not recommended near term.
• Inform your pharmacist about any other meds – co‑trimoxazole can interact with warfarin, certain diuretics and oral contraceptives.

Got more questions? Your GP or local pharmacy can give personalized advice. With the right dosage, monitoring, and a legit source, co‑trimoxazole is an effective tool against bacterial infections in the UK.