What is Trimethoprim Used For?

Trimethoprim is an antibiotic prescribed to treat urinary tract infections (UTIs), including cystitis. It is sometimes used to treat other infections, such as chest infections or acne, but at Prescription Doctor, we prescribe it specifically for cystitis.

What is trimethoprim used for?

Trimethoprim is an antibiotic used to treat bacterial infections, especially urinary tract infections. It is commonly prescribed for lower UTIs, such as cystitis in women.

Trimethoprim works by inhibiting the growth of bacteria responsible for causing cystitis. It does this by preventing the bacteria from producing folic acid, a vitamin that bacteria require for survival. For this reason, long-term use of trimethoprim may cause low folic acid blood levels in some patients. It is essential to complete your course of antibiotics to prevent the infection from recurring.

Most people notice an improvement in their cystitis symptoms within a few days. For more information on how long it takes for trimethoprim to work, please visit our blog.

How effective is trimethoprim for cystitis?

Studies show that for uncomplicated cystitis, trimethoprim can result in an eradication rate of the bacteria causing the infection of more than 90%. However, further research has shown that trimethoprim may be linked to an increased risk of acute kidney injury and high blood potassium levels compared to other antibiotics used to treat UTIs, so nitrofurantoin may be a more suitable alternative.

What is cystitis?

Cystitis is a UTI that affects the bladder. It is more common in women than men because women have a shorter urethra, the tube where pee passes out of the body, so bacteria can easily be spread from the bottom or during sex to the urethra.

Cystitis is commonly caused by the bacteria Escherichia coli (E.coli), but there are other causes, like:

• interstitial cystitis
• certain medications
• catheter use
• chemicals found in perfumed soap
• underlying medical conditions (diabetes, kidney stones, enlarged prostate)

Symptoms of cystitis

How to prevent cystitis

There are some things you can do to stop cystitis from coming back, including:

• wiping from the front to the back after going to the toilet
• urinating as soon as you can after having sex
• drinking plenty of water throughout the day
• avoiding using scented soaps, bubble baths or talcum powder
• washing your skin outside the vagina with water before and after sex
• having a shower instead of a bath
• avoiding spermicide with condoms or spermicide
• emptying your bladder fully when going for a pee
• limiting the amount of alcohol or coffee you drink
• using cranberry products like juice

Trimethoprim dosage

The usual trimethoprim dose that is prescribed for cystitis in adults is one 200 mg tablet twice a day for 3 days in women and 7 days for men.

How do you take trimethoprim?

Usually, you’ll take trimethoprim twice a day to treat cystitis, once in the morning and once in the evening.

You should swallow trimethoprim tablets whole with a glass of water with or without food.

You may have been prescribed trimethoprim for other reasons, which may change how you need to take it.

• If you are taking trimethoprim to prevent an infection, it is recommended that you take it at bedtime.
• If you have been prescribed trimethoprim to treat cystitis that starts after having sex, take a single dose within 2 hours of having sex.

How long do you take trimethoprim for cystitis?

Several factors can affect the duration of trimethoprim treatment for cystitis.

Trimethoprim alternatives

Mild cases of cystitis can often be treated effectively at home with painkillers, like paracetamol or ibuprofen, and over-the-counter cystitis relief sachets. At Prescription Doctor, we offer a range of cystitis treatments.

CanesOasis Cystitis Relief sachets contain 4g of sodium citrate, a type of salt that changes the pH of your urine, making it more alkaline. Doing so helps alleviate the stinging and discomfort you may feel when you have cystitis. The sachets have a cranberry flavour and are mixed with water to make a drinkable solution. Most people experience relief within 48 hours.

Some people may need antibiotics to clear up the infection and stop it from spreading further. Trimethoprim isn’t suitable for everyone, and often the first-choice antibiotic for cystitis and other UTIs is nitrofurantoin, also known as Macrobid.

Is nitrofurantoin better than trimethoprim for treating cystitis?

Nitrofurantoin is becoming the preferred treatment method for UTIs due to its low risk of bacterial resistance. Clinical studies have shown that nitrofurantoin is a suitable alternative to trimethoprim, the former first-line defence against cystitis.

A study comparing the effectiveness of nitrofurantoin and trimethoprim for uncomplicated cystitis found that the infection was cleared in 79% of patients treated with trimethoprim and 84% of those treated with nitrofurantoin. The researchers concluded that a 5-day course of nitrofurantoin was clinically equivalent to a 3-day course of trimethoprim for treating acute, uncomplicated cystitis in women.

Summary

Trimethoprim is an antibiotic used to treat cystitis. It is prescribed as a 3-day course for women, and most people notice an improvement in their symptoms within a few days.

You can get trimethoprim for cystitis if you are a woman from Prescription Doctor, or you can explore our range of treatments.

Authored & Reviewed By

Leanne Edermaniger

Medical Content Writer

Leanne is a science and health content writer focusing on human health and biology while utilising her solid academic background.

Published on: 15/08/2024 Reviewed on: 05/06/2025