What is Bactrim: Uses, Warnings & Interactions

How to take Bactrim

• Your doctor will tell you how much medicine to use. Use only directed.

• Take all of the medicine in your prescription to clear up your infection, even if you feel better after the first few doses.

• Tablets can be taken with or without food.

• Swallow the tablet whole with eight ounces of water. Drink plenty of fluids when taking Bactrim.

• The tablets have score lines that can be broken into two separate doses. This may be necessary when giving Bactrim to children. Ask the pharmacist to demonstrate if you don’t know how to divide a tablet.

• Store the medicine in a closed, light-resistant container at room temperature.

What to do if you miss a dose of Bactrim

• 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.

Bactrim contraindications

• This medicine is not right for everyone. 

• Do not use it if you have had an allergic reaction to trimethoprim, sulfamethoxazole, or any sulfa drug. 

• Bactrim should never be taken by people who:

  • Are pregnant

  • Are younger than 2 years of age

  • Have a history of drug-induced blood clotting problems due to sulfamethoxazole-trimethoprim

  • Have a history of anemia due to folate deficiency (vitamin B9 deficiency)

  • Have liver damage

  • Have severe kidney impairment

Bactrim warnings

• Tell any doctor or other healthcare provider who treats you that you are using this medicine.

• Your doctor may need to perform lab tests regularly to monitor the infection and the effects of this medicine. Keep all appointments.

• 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.

• Tell the doctor if you’re breastfeeding.

• Also, tell the prescribing doctor if you have:

  • Kidney problems

  • Liver damage

  • Problems absorbing nutrients from food

  • Malnourishment issues

  • Folate deficiency (low levels of vitamin B9)

  • Thyroid issues

  • A history of alcoholism

  • Severe allergies

  • Asthma

  • HIV/AIDS infection

  • Porphyria

  • A genetic disorder of the blood called G6PD deficiency

• This medicine may cause the following problems: 

  • Red blood cell death

  • Bleeding problems

  • Anemia

  • Kidney problems

  • Liver injury

  • Heart problems

  • Low blood sugar

  • Electrolyte imbalances, including high potassium and low sodium

  • Severe muscle damage

  • Severe drug or allergic reactions

• This medicine can cause severe diarrhea, which may occur several weeks or months after treatment ends. Call your doctor if you experience severe, watery, persistent, or bloody diarrhea. Do not take any medicine to treat the diarrhea until you have talked to your doctor. 

Bactrim interactions

• To avoid potentially hazardous drug interactions, tell the prescribing healthcare provider about all prescription drugs, over-the-counter medications, and supplements you use before taking Bactrim.

• Tell other healthcare providers you are using Bactrim before they prescribe new medications. Bactrim may affect some blood tests or interact with other drugs.

• Bactrim should never be taken with the heart medication dofetilide.

• Bactrim can cause problems when combined with certain medications. In some cases, healthcare professionals will avoid the combination if they can. Other combinations may require increased monitoring for side effects. These drugs include:

  • Drugs that make you pee (diuretics)

  • Blood pressure medications called ACE inhibitors or angiotensin receptor blockers

  • Oral diabetes drugs

  • Tricyclic antidepressants

  • Heart rhythm drugs

  • Cancer drugs and antimalarial drugs called antifolates

  • Amantadine, cyclosporine, digoxin, indomethacin, methotrexate, phenytoin, procainamide, pyrimethamine, warfarin, 

Find more detailed information about sulfamethoxazole-trimethoprim interactions to avoid here.