How and when to take trimethoprim

Always take trimethoprim as a doctor or pharmacist has told you and follow the instructions that come with your medicine.

Dosage and how to take trimethoprim

Dosage

Trimethoprim tablets contain 100mg or 200mg. The liquid contains 50mg in 5ml.

To treat urinary tract infections (UTIs) in adults, the usual dose is 200mg twice a day.

To prevent infections, the usual adult dose is 100mg once a day at night.

If you know what causes your cystitis, take one single dose of 200mg after you’ve been exposed to the trigger.

To treat acne, the usual adult dose is 300mg twice a day. This dose might be reduced over time.

The dose of trimethoprim you need to take depends on your condition, your age, and how well your kidneys work.

Doses are usually lower for children, older people and those with kidney problems.

Stopping trimethoprim

Carry on taking this medicine until you finish the course, even if you feel better. If you stop your treatment early, your problem could come back.

How to take trimethoprim

Trimethoprim tablets

If you're taking trimethoprim to treat an infection, you'll usually take it twice a day, once in the morning and once in the evening.

If you're taking trimethoprim once a day to prevent an infection, take it at bedtime.

If you know what triggers your cystitis and want to stop an infection before it starts, take trimethoprim as a single dose after being exposed to the trigger.

You can take trimethoprim with or without food.

Swallow trimethoprim tablets whole with a drink of water. Do not chew or break them.

You can take it as a liquid if you find it difficult to swallow tablets.

Trimethoprim liquid

If you're taking trimethoprim as a liquid, shake the bottle gently before measuring out the right amount using a medicine spoon or oral syringe. If you do not have an oral syringe or medicine spoon, ask your pharmacist for one. Do not use a kitchen teaspoon as it will not measure the right amount.

How long to take it for

How long you take trimethoprim for depends on the infection (how bad it is and where it is), your age, whether you're male or female and whether you have any other health problems.

The usual course of treatment is:

• 3 days for women and children with straightforward UTIs
• 7 days for men and pregnant women with straightforward UTIs
• 7 to 14 days for people with particularly severe or complicated UTIs, or a catheter
• 2 weeks for men with an acute UTI that has caused the prostate gland to swell (prostatitis), which may be continued for 4 weeks if a doctor thinks you need it.
• at least 3 months for people taking it for acne

If you're taking trimethoprim to help prevent UTIs, you'll usually be reviewed after 6 months. Depending on how well it has worked or if you've had any side effects, you may need to carry on with treatment, switch to another antibiotic or stop treatment.

It's very important to keep taking trimethoprim until your course is finished, even if you feel better. This helps stop the infection coming back.

If you forget to take it

If you forget to take a dose of trimethoprim, take it as soon as you remember, unless it's nearly time for your next dose. In this case, just leave out the missed dose and take your next dose at the usual time.

Never take 2 doses at the same time. Never take an extra dose to make up for a forgotten one.

If you often forget doses, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.

If you take too much

Taking 1 extra dose of trimethoprim is unlikely to harm you, but it may increase the chances of temporary side effects, such as feeling or being sick and diarrhoea.