Medically reviewed: December 15, 2017
What is sulfamethoxazole and trimethoprim?
Sulfamethoxazole and trimethoprim are both antibiotics that treat different types of infection caused by bacteria.
Sulfamethoxazole and trimethoprim is used a combination antibiotic used to treat ear infections, urinary tract infections, bronchitis, traveler's diarrhea, shigellosis, and Pneumocystis jiroveci pneumonia.
Sulfamethoxazole and trimethoprim may also be used for purposes not listed in this medication guide.
You should not use this medication if you have severe liver or kidney disease, anemia caused by folic acid deficiency, or a history of low blood platelets caused by taking trimethoprim or any sulfa drug.
Before taking this medicine
You should not use this medication if you are allergic to sulfamethoxazole or trimethoprim, or if you have:
severe liver or kidney disease;
anemia (low red blood cells) caused by folic acid deficiency; or
a history of low blood platelets caused by taking trimethoprim or any sulfa drug.
To make sure sulfamethoxazole and trimethoprim is safe for you, tell your doctor if you have:
kidney or liver disease;
a folic acid deficiency;
a thyroid disorder;
HIV or AIDS;
porphyria (a genetic enzyme disorder that causes symptoms affecting the skin or nervous system);
a glucose-6-phosphate dehydrogenase deficiency (G6PD deficiency); or
if you are malnourished.
FDA pregnancy category D. Do not use sulfamethoxazole and trimethoprim if you are pregnant. It could harm the unborn baby. Use effective birth control, and tell your doctor if you become pregnant during treatment.
This medicine can pass into breast milk and may harm a nursing baby. Tell your doctor if you are breast-feeding a baby.
Do not give this medication to a child younger than 2 months old.
How should I take sulfamethoxazole and trimethoprim?
Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended.
Shake the oral suspension (liquid) well just before you measure a dose. Measure the liquid with a special dose-measuring spoon or medicine cup. If you do not have a dose-measuring device, ask your pharmacist for one.
Use this medication for the full prescribed length of time. Your symptoms may improve before the infection is completely cleared. Skipping doses may also increase your risk of further infection that is resistant to antibiotics. Sulfamethoxazole and trimethoprim will not treat a viral infection such as the common cold or flu.
Drink plenty of fluids to prevent kidney stones while you are taking trimethoprim and sulfamethoxazole.
This medication can cause unusual results with certain medical tests. Tell any doctor who treats you that you are using sulfamethoxazole and trimethoprim.
Store at room temperature away from moisture, heat, and light.
What happens if I miss a dose?
Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.
What happens if I overdose?
Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.
What should I avoid while taking sulfamethoxazole and trimethoprim?
Antibiotic medicines can cause diarrhea, which may be a sign of a new infection. If you have diarrhea that is watery or bloody, stop taking this medication and call your doctor. Do not use anti-diarrhea medicine unless your doctor tells you to.
Avoid exposure to sunlight or tanning beds. This medication can make you sunburn more easily. Wear protective clothing and use sunscreen (SPF 30 or higher) when you are outdoors.
Sulfamethoxazole and trimethoprim side effects
Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have:
diarrhea that is watery or bloody;
pale skin, feeling light-headed or short of breath, rapid heart rate, trouble concentrating;
cold or flu symptoms, swollen gums, painful mouth sores, pain when swallowing, skin sores;
liver problems--upper stomach pain, tired feeling, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes); or
severe skin reaction--fever, sore throat, swelling in your face or tongue, burning in your eyes, skin pain, followed by a red or purple skin rash that spreads (especially in the face or upper body) and causes blistering and peeling.
Common side effects may include:
nausea, vomiting, loss of appetite; or
mild itching or rash.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
See also: Side effects (in more detail)
What other drugs will affect sulfamethoxazole and trimethoprim?
Tell your doctor about all medicines you use, and those you start or stop using during your treatment with sulfamethoxazole and trimethoprim, especially:
This list is not complete. Other drugs may interact with sulfamethoxazole and trimethoprim, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed in this medication guide.
Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
Copyright 1996-2018 Cerner Multum, Inc. Version: 8.01.
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- Drug class: sulfonamides