Merck Manual

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Trimethoprim and Sulfamethoxazole

Trimethoprim and Sulfamethoxazole


Common Uses

Some Side Effects


Trimethoprim/sulfamethoxazole (TMP/SMX)

Infections caused by susceptible bacteria that are resistant to other antibiotics, including methicillin-resistant Staphylococcus aureus (MRSA)

Chronic infection of the prostate (prostatitis)

Bladder infections in women

Prevention of recurring urinary tract infections (UTIs) in women and children

Intestinal infections due to various bacteria, such as Escherichia coli (E. coli)

Treatment and prevention of pneumonia due to Pneumocystis jirovecii (a fungus)

Nausea, vomiting, and diarrhea

Allergy (including rashes)

Crystals in urine (rare)

A decrease in white blood cell and platelet counts

Sensitivity to sunlight

Possibly increased tendency to bleed if used with warfarin

Kidney failure in people who have kidneys that are not functioning well

* Trimethoprim has side effects similar to those of sulfamethoxazole, but they are less common.