Skip to main content

Sulfamethoxazole/trimethoprim (By mouth)

Sulfamethoxazole (sul-fa-meth-OX-a-zole), Trimethoprim (trye-METH-oh-prim)

Treats or prevents infections. This medicine contains a sulfa drug (sulfonamide).

Brand Name(s):

Bactrim, Bactrim DS, SMZ-TMP Pediatric, Septra, Sulfatrim, Sulfatrim Pediatric

There may be other brand names for this medicine.

When This Medicine Should Not Be Used:

Do not use this medicine if you have had an allergic reaction to trimethoprim, sulfamethoxazole, or any sulfa drug. Do not use this medicine if you are pregnant, or in some situations if you have severe liver or kidney problems. Do not use this medicine if you have anemia caused by low levels of folic acid in your body. Do not use this medicine if you have a history of drug-induced thrombocytopenia.

How to Use This Medicine:

Liquid, Tablet

  • Take your medicine as directed.
  • Measure the oral liquid medicine with a marked measuring spoon, oral syringe, or medicine cup.
  • Drink extra fluids so you will urinate more often and help prevent kidney problems.
  • Take all of the medicine in your prescription to clear up your infection, even if you feel better after the first few doses.

If a dose is missed:

  • Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. Do not take extra medicine to make up for a missed dose.

How to Store and Dispose of This Medicine:

  • Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Do not freeze the oral liquid.
  • Ask your pharmacist, doctor, or health caregiver about the best way to dispose of any outdated medicine or medicine no longer needed.
  • Keep all medicine out of the reach of children. Never share your medicine with anyone.

Drugs and Foods to Avoid:

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • Make sure your doctor knows if you also use digoxin (Lanoxin®), indomethacin (Indocin®), a diuretic (water pill, such as hydrochlorothiazide), ACE inhibitor blood pressure medicine (such as benazepril, enalapril, lisinopril, Lotrel®, Vasotec®, Zestoretic®, Zestril®), or a blood thinner (such as warfarin, Coumadin®, Jantoven®).
  • Make sure your doctor knows if you also use amantadine (Symmetrel®), cyclosporine (Gengraf®, Neoral®, Sandimmune®), memantine (Namenda®), methotrexate (Rheumatrex®, Trexall®), phenytoin (Dilantin®) or other seizure medicine, medicine to treat depression (such as amitriptyline, nortriptyline, Elavil®), diabetes medicine that you take by mouth (such as glimepiride, glyburide, metformin, pioglitizone, Actos®, Avandia®, Janumet®, Januvia®), or medicine to prevent malaria (such as pyrimethamine, Daraprim®).

Warnings While Using This Medicine:

  • It is not safe to take this medicine during pregnancy. It could harm an unborn baby. Tell your doctor right away if you become pregnant.
  • Make sure your doctor knows if you are breastfeeding, or if you have kidney disease, liver disease, diabetes, malabsorption or malnutrition, folate deficiency, porphyria, thyroid problems, or a history of alcoholism. Tell your doctor if you have asthma or severe allergies, especially if you are allergic to any medicines. It is important for your doctor to know if you have HIV or AIDS, because this medicine might work differently. Tell your doctor if you have glucose-6-phosphate dehydrogenase (G6PD) deficiency, a rare condition.
  • Very rarely, this medicine has caused severe side effects. If you start to have a skin rash, or if you think you are having a severe reaction, stop taking this medicine and call your doctor right away. Signs of a severe reaction include a sore throat, fever, muscle pain, cough, trouble breathing, skin rash, purple spots on your skin, or very pale or yellow skin.
  • This medicine may cause mineral imbalance, such as high potassium levels or low sodium levels in the blood. Tell your doctor right away if you have confusion, weakness, muscle twitching, uneven heartbeat, trouble breathing, or numbness or tingling in your hands, feet, or lips.
  • This medicine may lower the number of platelets in your body, which are necessary for proper blood clotting. This may cause you to bleed or get infections more easily. Talk with your doctor if you have concerns about this.
  • Ask your doctor before you take any medicine to stop severe diarrhea.Check with your doctor if the diarrhea continues. Diarrhea may occur 2 months after you stop taking this medicine.
  • Tell any doctor or dentist who treats you that you are using this medicine. This medicine may affect certain medical test results.
  • Your doctor will do lab tests at regular visits to check on the effects of this medicine. Keep all appointments.

Possible Side Effects While Using This Medicine:

Call your doctor right away if you notice any of these side effects:

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Blistering, peeling, or red skin rash
  • Dark-colored urine or pale stools, nausea, vomiting, loss of appetite, pain in your upper stomach, yellow skin or eyes
  • Chest pain, cough, or trouble breathing
  • Confusion, weakness
  • Muscle twitching
  • Increased hunger or shakiness
  • Severe diarrhea, stomach pain, cramps, bloating
  • Sore throat, fever, muscle pain, skin changes
  • Uneven heartbeat, numbness or tingling in your hands, feet, or lips
  • Unusual bleeding, bruising, or weakness

If you notice these less serious side effects, talk with your doctor:

  • Nausea, vomiting, loss of appetite

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Last Updated: 4/4/2014

Copyright © 1984- Thomson Micromedex. All rights reserved.

Thomson & A.D.A.M