Medically reviewed on September 5, 2018
Uses of Bactrim:
- It is used to treat or prevent bacterial infections.
What do I need to tell my doctor BEFORE I take Bactrim?
For all patients taking Bactrim (sulfamethoxazole and trimethoprim tablets):
- If you have an allergy to sulfamethoxazole, trimethoprim, or any other part of Bactrim (sulfamethoxazole and trimethoprim tablets).
- If you are allergic to any drugs like this one, any other drugs, foods, or other substances. Tell your doctor about the allergy and what signs you had, like rash; hives; itching; shortness of breath; wheezing; cough; swelling of face, lips, tongue, or throat; or any other signs.
- If you have anemia caused by a lack of folic acid.
- If you have any of these health problems: Kidney disease or liver disease.
- If you have any of these health problems: Asthma, porphyria, thyroid disease, not enough folate in the body, poor absorption, or poor nutrition.
- If you have been drinking alcohol for a long time or are taking a drug for seizures.
- If you have ever had a low platelet count when using trimethoprim or a sulfa (sulfonamide) drug.
- If you are taking any of these drugs: Amantadine, cyclosporine, dofetilide, indomethacin, leucovorin, methotrexate, or pyrimethamine.
- If you are taking or have recently taken any of these drugs: Benazepril, captopril, enalapril, fosinopril, lisinopril, moexipril, perindopril, quinapril, ramipril, or trandolapril.
- If you are taking a water pill.
- If you are breast-feeding or plan to breast-feed.
- If your child is younger than 2 months of age. Do not give Bactrim (sulfamethoxazole and trimethoprim tablets) to an infant younger than 2 months of age.
This is not a list of all drugs or health problems that interact with Bactrim (sulfamethoxazole and trimethoprim tablets).
Tell your doctor and pharmacist about all of your drugs (prescription or OTC, natural products, vitamins) and health problems. You must check to make sure that it is safe for you to take Bactrim (sulfamethoxazole and trimethoprim tablets) with all of your drugs and health problems. Do not start, stop, or change the dose of any drug without checking with your doctor.
What are some things I need to know or do while I take Bactrim?
- Tell all of your health care providers that you take Bactrim (sulfamethoxazole and trimethoprim tablets). This includes your doctors, nurses, pharmacists, and dentists.
- Have blood work checked as you have been told by the doctor. Talk with the doctor.
- Have your urine checked as you have been told by your doctor.
- This medicine may affect certain lab tests. Tell all of your health care providers and lab workers that you take Bactrim (sulfamethoxazole and trimethoprim tablets).
- Do not use longer than you have been told. A second infection may happen.
- Be careful if you have G6PD deficiency. Anemia may happen.
- If you have high blood sugar (diabetes), you will need to watch your blood sugar closely.
- Talk with your doctor before you drink alcohol.
- This medicine may make you sunburn more easily. Use care if you will be in the sun. Tell your doctor if you sunburn easily while taking this drug.
- This medicine may affect how much of some other drugs are in your body. If you are taking other drugs, talk with your doctor. You may need to have your blood work checked more closely while taking Bactrim (sulfamethoxazole and trimethoprim tablets) with your other drugs.
- Rarely, very bad effects have happened with sulfa drugs. Sometimes, these have been deadly. These effects have included liver problems, blood problems, and very bad skin reactions (Stevens-Johnson syndrome/toxic epidermal necrolysis). Call your doctor right away if you have a rash; red, swollen, blistered, or peeling skin; red or irritated eyes; sores in your mouth, throat, nose, or eyes; fever, chills, or sore throat; cough that is new or worse; feeling very tired or weak; any bruising or bleeding; or signs of liver problems like dark urine, feeling tired, not hungry, upset stomach or stomach pain, light-colored stools, throwing up, or yellow skin or eyes.
- This medicine may raise the chance of a very bad brain problem called aseptic meningitis. Call your doctor right away if you have a headache, fever, chills, very upset stomach or throwing up, stiff neck, rash, bright lights bother your eyes, feeling sleepy, or feeling confused.
- If you are 65 or older, use Bactrim (sulfamethoxazole and trimethoprim tablets) with care. You could have more side effects.
- This medicine may cause harm to the unborn baby if you take it while you are pregnant. If you are pregnant or you get pregnant while taking Bactrim (sulfamethoxazole and trimethoprim tablets), call your doctor right away.
How is this medicine (Bactrim) best taken?
Use Bactrim (sulfamethoxazole and trimethoprim tablets) as ordered by your doctor. Read all information given to you. Follow all instructions closely.
- Drink lots of noncaffeine liquids unless told to drink less liquid by your doctor.
- Take with or without food. Take with food if it causes an upset stomach.
- Take with a full glass of water.
- Take Bactrim (sulfamethoxazole and trimethoprim tablets) at the same time of day.
- To gain the most benefit, do not miss doses.
- Keep taking Bactrim (sulfamethoxazole and trimethoprim tablets) as you have been told by your doctor or other health care provider, even if you feel well.
What do I do if I miss a dose?
- Take a missed dose as soon as you think about it.
- If it is close to the time for your next dose, skip the missed dose and go back to your normal time.
- Do not take 2 doses at the same time or extra doses.
See also: Dosage Information (in more detail)
What are some side effects that I need to call my doctor about right away?
WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:
- Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
- Signs of a high potassium level like a heartbeat that does not feel normal; change in thinking clearly and with logic; feeling weak, lightheaded, or dizzy; feel like passing out; numbness or tingling; or shortness of breath.
- Signs of low blood sugar like dizziness, headache, feeling sleepy, feeling weak, shaking, a fast heartbeat, confusion, hunger, or sweating.
- Signs of kidney problems like unable to pass urine, change in how much urine is passed, blood in the urine, or a big weight gain.
- Signs of low sodium levels like headache, trouble focusing, memory problems, feeling confused, weakness, seizures, or change in balance.
- Muscle or joint pain.
- Purple patches on the skin or mouth.
- Shortness of breath.
- Hallucinations (seeing or hearing things that are not there).
- Mood changes.
- It is common to have diarrhea when taking Bactrim (sulfamethoxazole and trimethoprim tablets). Rarely, a very bad form of diarrhea called Clostridium difficile (C diff)–associated diarrhea (CDAD) may occur. Sometimes, this has led to a deadly bowel problem (colitis). CDAD may happen while you are taking Bactrim (sulfamethoxazole and trimethoprim tablets) or within a few months after you stop taking it. Call your doctor right away if you have stomach pain or cramps, very loose or watery stools, or bloody stools. Do not try to treat loose stools without first checking with your doctor.
What are some other side effects of Bactrim?
All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:
- Upset stomach or throwing up.
- Loose stools (diarrhea).
- Not hungry.
These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.
You may report side effects to the FDA at 1-800-FDA-1088. You may also report side effects at http://www.fda.gov/medwatch.
See also: Side effects (in more detail)
If OVERDOSE is suspected:
If you think there has been an overdose, call your poison control center or get medical care right away. Be ready to tell or show what was taken, how much, and when it happened.
How do I store and/or throw out Bactrim?
- Store at room temperature.
- Store in a dry place. Do not store in a bathroom.
- Protect from light.
- Keep all drugs in a safe place. Keep all drugs out of the reach of children and pets.
- Throw away unused or expired drugs. Do not flush down a toilet or pour down a drain unless you are told to do so. Check with your pharmacist if you have questions about the best way to throw out drugs. There may be drug take-back programs in your area.
Consumer information use
- If your symptoms or health problems do not get better or if they become worse, call your doctor.
- Do not share your drugs with others and do not take anyone else's drugs.
- Keep a list of all your drugs (prescription, natural products, vitamins, OTC) with you. Give this list to your doctor.
- Talk with the doctor before starting any new drug, including prescription or OTC, natural products, or vitamins.
- Some drugs may have another patient information leaflet. Check with your pharmacist. If you have any questions about Bactrim (sulfamethoxazole and trimethoprim tablets), please talk with your doctor, nurse, pharmacist, or other health care provider.
- If you think there has been an overdose, call your poison control center or get medical care right away. Be ready to tell or show what was taken, how much, and when it happened.
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
More about Bactrim (sulfamethoxazole / trimethoprim)
- Bactrim Side Effects
- During Pregnancy
- Dosage Information
- Patient Tips
- Drug Images
- Drug Interactions
- Compare Alternatives
- Support Group
- Pricing & Coupons
- En Español
- 322 Reviews
- Generic Availability
- Drug class: sulfonamides