Drug Database: 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:

• Chronic bronchitis
• Urinary tract and acute ear infections
• Enteric infections, including shigellosis and traveler's diarrhea
• Pneumocystis pneumonia (PCP)

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?

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

• PCP
• Certain bacterial enteric infections, including shigellosis and salmonellosis (also known as Salmonella infection)
• Cystoisosporiasis (also called isosporiasis)
• Toxoplasma gondii encephalitis

• PCP from occurring the first time and from recurring
• Bacterial enteric infections from occurring the first time
• Toxoplasma gondii encephalitis from occurring the first time and from recurring
• Cystoisosporiasis from recurring
• Spontaneous bacterial peritonitis (SBP) associated with hepatitis B virus infection from recurring. (SBP is an infection of fluid build-up in the abdomen, having no known cause.)

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

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

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

• If you are allergic to sulfamethoxazole, sulfonamides (sulfa medicines), sulfites, 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 using 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 breast/chestfeeding or plan to breast/chestfeed. For people with HIV in the United States, the Guideline recommends speaking with your health care provider to discuss options for feeding your baby. People with suppressed viral load have a less than 1% chance of transmitting HIV to their baby via their own milk.
• 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 use sulfamethoxazole/trimethoprim?

Use sulfamethoxazole/trimethoprim according to your health care provider’s instructions. Your health care provider will tell you how much sulfamethoxazole/trimethoprim to use and when to use 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?

• 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 vials of 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?

• Recommendations on the HIV-related uses of sulfamethoxazole/trimethoprim, from the Guidelines for the Prevention and Treatment of Opportunistic Infections in Adults and Adolescents with HIV and the Guidelines for the Prevention and Treatment of Opportunistic Infections in Children with and Exposed to HIV.
• This Patient Version drug summary is based on the following FDA label(s): Injection; Suspension; Tablet, tablet (double strength).
• The American Hospital Formulary Service (AHFS) Patient Medication Information for co-trimoxazole injection and co-trimoxazole available from MedlinePlus.
• Sulfamethoxazole/trimethoprim-related research studies, from ClinicalTrials.gov. (The ClinicalTrials.gov search can be modified so that you can get results that better match your interests. To learn more about the ClinicalTrials.gov search features, please see How to Search.)