Trimethoprim

What is trimethoprim?

Trimethoprim is an antibiotic that is used to treat and prevent urine infections (also called urinary tract infections or UTIs). It works by killing or stopping the growth of bacteria (bugs) and getting rid of the infection. 

Can I get trimethoprim from my pharmacy without a prescription?

Many pharmacists are now able to sell trimethoprim for the treatment of UTIs. This is available without a prescription to women aged between 16 to 65 years, who are not pregnant and do not have any other complicating factors.

Only pharmacists who have completed additional training can supply trimethoprim. They will need to ask you questions to make sure it is the best option for you and will need to record your name and address. 

Dose

In New Zealand, trimethoprim is available as tablets (300 mg).

• To treat an infection: The usual dose for adults with an infection is 1 tablet (300mg), each night. Your doctor or pharmacist will advise you how long to take trimethoprim for (usually 3 to 7 days).
• To prevent an infection: The dose to prevent infection is half a tablet (150mg) at night. If you have frequent urine infections, you will have to take trimethoprim each night for a few months to prevent recurrent infections.
• Always take your trimethoprim exactly as your doctor has told you. The pharmacy label on your medicine will tell you how much trimethoprim to take, how often to take it, and any special instructions.

How to take trimethoprim

• Timing of your dose: You can take trimethoprim with or without food. If you get stomach upset, try taking it with food. Trimethoprim is best taken before bedtime. Take trimethoprim at the same time each day. 
• Splitting tablets: If your dose is half a tablet, you can split the tablet into two by either breaking the tablet along a scored line, or using a tablet cutter. You can buy a tablet cutter from your pharmacy. If you have trouble splitting your tablets, talk to your pharmacist, they can do this for you. It’s important to halve tablets correctly because uneven splitting or crumbling, changes the dose.
• Missed dose: If you forget to take trimethoprim, take it as soon as you remember. But, if it is nearly time for your next dose, just take the next dose at the right time. Do not take double the dose.
• Finish the course: It is best to take the whole course of antibiotics for the number of days your doctor has told you to. Do not stop taking it, even if you feel your infection has cleared up.  

Things to consider while you are taking trimethoprim

• Trimethoprim does not have direct interaction with alcohol. This means that most people could have the occasional drink while taking it without any serious problems. However, if trimethoprim makes you feel sick (nausea), do not drink alcohol as it will make you feel worse.
• If you are taking the contraceptive pill, you do not usually need to use additional contraception if you're taking trimethoprim. But if the antibiotic or the illness they're treating cause diarrhoea or vomiting, lasting more than 24 hours, absorption of the contraceptive pill may be affected. If this happens, ask your doctor or pharmacist for advice about contraception over the following few days.

Possible side effects 

Like all medicines, trimethoprim can cause side effects, although not everyone gets them. Often side effects improve as your body adjusts to the new medicine

Learn More

Medsafe Consumer Information Sheet   TMP Tablet

New Zealand Formulary Patient Information: trimethoprim

References

1. Trimethoprim New Zealand Formulary

Useful resources for healthcare professionals

TMP Tablet Medsafe, NZ
Upfront – antimicrobial resistance in NZ – what is my role in primary care? BPAC, NZ, 2013
Antibiotics guide BPAC, NZ, 2013