Sulfamethoxazole and trimethoprim are both antibiotics that treat different types of infection caused by bacteria.

The combination of sulfamethoxazole and trimethoprim is used to treat ear infections, urinary tract infections, bronchitis, traveler's diarrhea, and Pneumocystis carinii pneumonia.

Sulfamethoxazole and trimethoprim may also be used for purposes not listed in this medication guide.

You should not use this medication if you are allergic to sulfamethoxazole or trimethoprim, if you are pregnant or breast-feeding, or if you have anemia (lack of red blood cells) caused by folic acid deficiency.

Before using sulfamethoxazole and trimethoprim, tell your doctor if you have kidney or liver disease, a folic acid deficiency, asthma or severe allergies, AIDS, a glucose-6-phosphate dehydrogenase deficiency (G6PD deficiency), or if you are malnourished.

Take this medication for the full prescribed length of time. Your symptoms may improve before the infection is completely cleared. Sulfamethoxazole and trimethoprim will not treat a viral infection such as the common cold or flu.

Antibiotic medicines can cause diarrhea, which may be a sign of a new infection. If you have diarrhea that is watery or has blood in it, call your doctor. Do not use any medicine to stop the diarrhea unless your doctor has told you to.

Avoid exposure to sunlight or tanning beds. Sulfamethoxazole and trimethoprim can make you sunburn more easily. Wear protective clothing and use sunscreen (SPF 30 or higher) when you are outdoors.

You should not use this medication if you are allergic to sulfamethoxazole or trimethoprim, if you are pregnant or breast-feeding, or if you have anemia (lack of red blood cells) caused by folic acid deficiency.

To make sure you can safely take sulfamethoxazole and trimethoprim, tell your doctor if you have any of these other conditions:

• kidney or liver disease;

• a folic acid deficiency;

• asthma or severe allergies;

• AIDS;

• a glucose-6-phosphate dehydrogenase deficiency (G6PD deficiency); or

• if you are malnourished.

FDA pregnancy category C. It is not known whether sulfamethoxazole and trimethoprim will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant while using this medication.

Sulfamethoxazole and trimethoprim can pass into breast milk and may harm a nursing baby. Do not use this medication without telling your doctor if you are breast-feeding a baby.

Do not give this medication to a child younger than 2 months old.

Older adults may be more likely to have side effects from this medicine.