Drug information

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Other Names
Bactrim, Bactrim DS, SMX-TMP, Septra, Sulfamethoprim, Sulfamethoprim-DS, Sulfatrim, TMP-SMX
Drug Class
Antibacterial (Sulfonamide/Dihydrofolate Reductase Inhibitor)
What is sulfamethoxazole/trimethoprim?What is sulfamethoxazole/trimethoprim?

What is sulfamethoxazole/trimethoprim?

Sulfamethoxazole/trimethoprim is an antibacterial prescription medicine approved by the U.S. Food and Drug Administration (FDA) for the treatment of certain infections, such as:

Sulfamethoxazole/trimethoprim is also FDA-approved to prevent PCP in people who are immunosuppressed and are at risk of developing PCP.

Certain bacterial infections and PCP can be opportunistic infections (OIs) of HIV. An OI is an infection that occurs more frequently or is more severe in people with weakened immune systems—such as people with HIV—than in people with healthy immune systems. To learn more about OIs, read the HIVinfo What is an Opportunistic Infection? fact sheet.

How is sulfamethoxazole/trimethoprim used in people with HIV?How is sulfamethoxazole/trimethoprim used in people with HIV?

How is sulfamethoxazole/trimethoprim used in people with HIV?

The Guidelines for the Prevention and Treatment of Opportunistic Infections in Adults and Adolescents with HIV include recommendations on the uses of sulfamethoxazole/trimethoprim in people with HIV to:

Treat: Prevent:
  • PCP from occurring the first time and from recurring
  • Bacterial enteric infections from occurring the first time
  • Toxoplasmosis from occurring the first time and from recurring
  • Cystoisosporiasis from recurring

The recommended uses may not always be consistent with FDA-approved uses of sulfamethoxazole/trimethoprim. See the Guidelines for complete information on recommended uses of sulfamethoxazole/trimethoprim in adults and adolescents with HIV. Sulfamethoxazole/trimethoprim may have other recommended uses not listed above.

What should I tell my health care provider before taking sulfamethoxazole/trimethoprim?What should I tell my health care provider before taking sulfamethoxazole/trimethoprim?

What should I tell my health care provider before taking sulfamethoxazole/trimethoprim?

Before taking sulfamethoxazole/trimethoprim, tell your health care provider:

  • If you are allergic to sulfamethoxazole, sulfonamides (sulfa medicines), trimethoprim, or any other medicines.
  • About any medical conditions you have or have had, including:
    • Kidney or liver problems
    • Folate deficiency (low levels of folic acid in the blood)
    • Severe allergies or asthma
    • Inherited blood disorders: porphyria or glucose-6-phosphate dehydrogenase (G-6PD) deficiency
    • Thyroid problems
  • About anything that could affect your ability to take medicines, such as difficulty swallowing pills, difficulty remembering to take pills, or any health conditions that may prevent your use of intravenous medicines.
  • If you are pregnant or plan to become pregnant. Sulfamethoxazole/trimethoprim should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Talk to your health care provider about the risks and benefits of taking sulfamethoxazole/trimethoprim during pregnancy. The Guidelines for the Prevention and Treatment of Opportunistic Infections in Adults and Adolescents with HIV may include other recommendations on the use of sulfamethoxazole/trimethoprim during pregnancy. Please refer to these guidelines for additional information.
  • If you are breastfeeding or plan to breastfeed. For women with HIV in the United States, the Guideline does not recommend breastfeeding. Before your baby is born, or if you are already breastfeeding, talk to your health care provider to discuss alternative options for feeding your baby.
  • About other prescription and nonprescription medicines, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Sulfamethoxazole/trimethoprim may affect the way other medicines or products work, and other medicines or products may affect how sulfamethoxazole/trimethoprim works. Ask your health care provider if there are interactions between sulfamethoxazole/trimethoprim and the other medicines you take.

Ask your health care provider about possible side effects from sulfamethoxazole/trimethoprim. Your health care provider will tell you what to do if you have side effects.

How should I take sulfamethoxazole/trimethoprim?How should I take sulfamethoxazole/trimethoprim?

How should I take sulfamethoxazole/trimethoprim?

Take sulfamethoxazole/trimethoprim according to your health care provider’s instructions. Your health care provider will tell you how much sulfamethoxazole/trimethoprim to take and when to take it. Before you start sulfamethoxazole/trimethoprim and each time you get a refill, read any printed information that comes with your medicine.

How should sulfamethoxazole/trimethoprim be stored?How should sulfamethoxazole/trimethoprim be stored?

How should sulfamethoxazole/trimethoprim be stored?

  • Store sulfamethoxazole/trimethoprim oral suspension at room temperature, 68°F to 77°F (20°C to 25°C). Protect the oral suspension from light.
  • Store sulfamethoxazole/trimethoprim tablets at room temperature, 68°F to 77°F (20°C to 25°C).
  • Store sulfamethoxazole/trimethoprim injection solution at room temperature, 68°F to 77°F (20°C to 25°C). Do not refrigerate the injection solution.
  • Do not use sulfamethoxazole/trimethoprim if the original seal of the container is broken or missing.
  • Throw away sulfamethoxazole/trimethoprim that is no longer needed or expired (out of date). Follow FDA guidelines on how to safely dispose of unused medicine.
  • Keep sulfamethoxazole/trimethoprim and all medicines out of reach of children.
Where can I find more information about sulfamethoxazole/trimethoprim?Where can I find more information about sulfamethoxazole/trimethoprim?

Where can I find more information about sulfamethoxazole/trimethoprim?

Last Reviewed: January 14, 2021