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Generic Name: sulfamethoxazole/trimethoprim (SUL-fa-meth-OX-a-zole/trye-METH-oh-prim)
Brand Name: Examples include Bactrim and Bactrim DS

Bactrim is used for:

Treating infections caused by certain bacteria. It is also used to prevent certain infections.

Bactrim is an antibiotic combination containing a sulfonamide antibiotic. It works by killing sensitive bacteria.

Do NOT use Bactrim if:

  • you are allergic to any ingredient in Bactrim or to any other sulfonamide (sulfa) medicine (eg, glipizide, hydrochlorothiazide)
  • you have a history of low blood platelet levels (immune thrombocytopenia) caused by trimethoprim or a sulfa medicine
  • you have liver damage or severe kidney problems
  • you have anemia caused by low levels of folate in the blood
  • the patient is a child younger than 2 months old
  • you are taking dofetilide or methenamine

Contact your doctor or health care provider right away if any of these apply to you.

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Before using Bactrim:

Some medical conditions may interact with Bactrim. Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you:

  • if you are pregnant, planning to become pregnant, or are breast-feeding
  • if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
  • if you have allergies to medicines, foods, or other substances
  • if you have liver or kidney problems, certain blood problems (eg, anemia, porphyria), thyroid problems, asthma, glucose-6-phosphate dehydrogenase (G6PD) deficiency, or HIV infection
  • if you have low levels of folate in the blood or are at risk for low blood folate levels (eg, you have alcoholism, you are elderly, you do not absorb nutrients from food properly, you are in a poor nutritional state, you are taking medicine for seizures)
  • if you have a history of high blood potassium levels

Some MEDICINES MAY INTERACT with Bactrim. Tell your health care provider if you are taking any other medicines, especially any of the following:

  • Angiotensin-converting enzyme (ACE) inhibitors (eg, enalapril), diuretics (eg, hydrochlorothiazide), or indomethacin because they may increase the risk of Bactrim's side effects
  • Anticoagulants (eg, warfarin) because the risk of bleeding may be increased
  • Dofetilide because the risk of its side effects, including severe irregular heartbeat, may be increased by Bactrim
  • Pyrimethamine because it is possible that a certain type of anemia may develop
  • Methenamine because certain urinary problems may occur
  • Amantadine, digoxin, hydantoins (eg, phenytoin), methotrexate, sulfones (eg, dapsone), or oral medicine for diabetes (eg, glipizide, metformin, pioglitazone) because the risk of their side effects may be increased by Bactrim
  • Tricyclic antidepressants (eg, amitriptyline) because their effectiveness may be decreased by Bactrim
  • Cyclosporine because its effectiveness may be decreased and the risk of kidney side effects may be increased

This may not be a complete list of all interactions that may occur. Ask your health care provider if Bactrim may interact with other medicines that you take. Check with your health care provider before you start, stop, or change the dose of any medicine.

How to use Bactrim:

Use Bactrim as directed by your doctor. Check the label on the medicine for exact dosing instructions.

  • Take Bactrim by mouth with or without food.
  • Bactrim works best if it is taken at the same time(s) each day.
  • Take Bactrim with a full glass of water (8 oz [240 mL]). Drinking extra fluids while you are taking Bactrim is recommended. Check with your doctor for instructions.
  • To clear up your infection completely, take Bactrim for the full course of treatment. Keep taking it even if you feel better in a few days.
  • If you are using Bactrim to prevent an infection, continue to take it even if you feel well. Do not miss any doses.
  • If you miss a dose of Bactrim, take it as soon as possible. If it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not take 2 doses at once.

Ask your health care provider any questions you may have about how to use Bactrim.

Important safety information:

  • Bactrim may cause you to become sunburned more easily. Avoid the sun, sunlamps, or tanning booths until you know how you react to Bactrim. Use a sunscreen or wear protective clothing if you must be outside for more than a short time.
  • Mild diarrhea is common with antibiotic use. However, a more serious and sometimes fatal form of diarrhea (pseudomembranous colitis) may rarely occur. This may develop while you use the antibiotic or within several months after you stop using it. Contact your doctor right away if stomach pain or cramps, severe diarrhea, or bloody stools occur. Do not treat diarrhea without first checking with your doctor.
  • Be sure to use Bactrim for the full course of treatment. If you do not, the medicine may not clear up your infection completely. The bacteria could also become less sensitive to this or other medicines. This could make the infection harder to treat in the future.
  • Bactrim only works against bacteria; it does not treat viral infections (eg, the common cold).
  • Long-term or repeated use of Bactrim may cause a second infection. Tell your doctor if signs of a second infection occur. Your medicine may need to be changed to treat this.
  • A very bad skin reaction (Stevens-Johnson syndrome/toxic epidermal necrolysis) may happen. It can cause very bad health problems that may not go away and sometimes death. Get medical help right away if you have signs like red, swollen, blistered, or peeling skin (with or without fever); red or irritated eyes; or sores in your mouth, throat, nose, or eyes.
  • Severe and sometimes fatal liver problems have happened in patients taking Bactrim. Tell your doctor right away if you develop symptoms of liver problems (eg, dark urine; pale stools; severe or persistent nausea or vomiting, loss of appetite, or stomach pain; unusual tiredness; yellowing of skin or eyes).
  • Serious and sometimes fatal blood problems may happen. Contact your doctor immediately if you develop fever, chills, or sore throat; joint pain; pale skin; unusual bruising or bleeding; or unusual tiredness or weakness.
  • Bactrim may cause serious lung problems. Tell your doctor right away if you develop a cough, shortness of breath, or chest pain.
  • Patients taking Bactrim to treat a certain type of pneumonia should avoid taking leucovorin. It may decrease Bactrim's effectiveness. Talk with your doctor if you are taking leucovorin.
  • Do not receive a live vaccine (eg, measles, mumps) while you are taking Bactrim. Talk with your doctor before you receive any vaccine.
  • Diabetes patients - Bactrim may affect your blood sugar. Check blood sugar levels closely. Ask your doctor before you change the dose of your diabetes medicine.
  • Bactrim may interfere with certain lab tests. Be sure your doctor and lab personnel know you are taking Bactrim.
  • Lab tests, including complete blood cell counts, blood potassium levels, and kidney function, may be performed while you use Bactrim. These tests may be used to monitor your condition or check for side effects. Be sure to keep all doctor and lab appointments.
  • Use Bactrim with caution in the ELDERLY; they may be more sensitive to its effects, especially severe skin reactions, bone marrow problems, or high blood potassium levels.
  • Bactrim should not be used in CHILDREN younger than 2 months old; safety and effectiveness in these children have not been confirmed.
  • PREGNANCY and BREAST-FEEDING: Bactrim may cause harm to the fetus. If you think you may be pregnant, contact your doctor. You will need to discuss the benefits and risks of using Bactrim while you are pregnant. Bactrim is found in breast milk. If you are or will be breast-feeding while you use Bactrim, check with your doctor. Discuss any possible risks to your baby.

Possible side effects of Bactrim:

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome:

Appetite loss; mild diarrhea; nausea; vomiting.

Seek medical attention right away if any of these SEVERE side effects occur:

Severe allergic reactions (rash; hives; itching; difficulty breathing or swallowing; tightness in the chest; swelling of the mouth, face, lips, throat, or tongue; unusual hoarseness); bloody or black, tarry stools; change in the amount of urine produced; confusion; decreased urination; fast or irregular heartbeat; hallucinations; joint or muscle pain; lower back or flank pain; mental or mood changes (eg, depression); painful or stiff neck; purple patches under the skin; seizures; severe or persistent diarrhea; severe or persistent headache; severe or persistent nausea or vomiting; severe stomach or back pain (with or without nausea or vomiting); stomach cramps; swelling or soreness of the mouth or tongue; symptoms of low blood sugar (eg, increased sweating, weakness, tremors, dizziness, fainting, drowsiness, headache, chills, fast heartbeat, vision changes, increased hunger); vaginal irritation or discharge; vomit that looks like coffee grounds.

This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider. Call your doctor for medical advice about side effects. To report side effects to the appropriate agency, please read the Guide to Reporting Problems to FDA.

If OVERDOSE is suspected:

Contact 1-800-222-1222 (the American Association of Poison Control Centers), your local poison control center, or emergency room immediately.

Proper storage of Bactrim:

Store Bactrim at room temperature, between 68 and 77 degrees F (20 and 25 degrees C). Store away from heat, moisture, and light. Keep in a tight, light-resistant container. Do not store in the bathroom. Keep Bactrim out of the reach of children and away from pets.

General information:

  • If you have any questions about Bactrim, please talk with your doctor, pharmacist, or other health care provider.
  • Bactrim is to be used only by the patient for whom it is prescribed. Do not share it with other people.
  • If your symptoms do not improve or if they become worse, check with your doctor.
  • Check with your pharmacist about how to dispose of unused medicine.

This information should not be used to decide whether or not to take Bactrim or any other medicine. Only your health care provider has the knowledge and training to decide which medicines are right for you. This information does not endorse any medicine as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about Bactrim. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to Bactrim. This information is not specific medical advice and does not replace information you receive from your health care provider. You must talk with your healthcare provider for complete information about the risks and benefits of using Bactrim.

Issue Date: December 3, 2014
Database Edition 14.4.1.003
Copyright © 2014 Wolters Kluwer Health, Inc.

Disclaimer: This information should not be used to decide whether or not to take this medicine or any other medicine. Only your health care provider has the knowledge and training to decide which medicines are right for you. This information does not endorse any medicine as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this medicine. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this medicine. This information is not specific medical advice and does not replace information you receive from your health care provider. You must talk with your healthcare provider for complete information about the risks and benefits of using this medicine.

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