Find & Manage Your Patient Assistance Programs
Estimated patient savings $600,000,000.00

Important Note

The following information is intended to supplement, not substitute for, the expertise and judgment of your physician, pharmacist or other healthcare professional. It should not be construed to indicate that use of the drug is safe, appropriate, or effective for you. Consult your healthcare professional before using this drug.



COMMON BRAND NAME(S): Proloprim, Trimpex


Trimethoprim is an antibiotic used to treat a bacterial infection.

How To Use

This medication is best taken on an empty stomach, but may be taken with food or milk if stomach upset occurs. Antibiotics work best when the amount of medicine in your body is kept at a constant level. Do this by taking the medication at evenly spaced intervals throughout the day and night. Continue to take this medication until the full prescribed amount is finished even if symptoms disappear after a few days. Stopping the medication too early may allow bacteria to continue to grow resulting in a relapse of the infection.

Side Effects

May cause stomach upset, diarrhea, loss of appetite, nausea, and headache during the first few days as your body adjusts to the medication. If these symptoms persist or become severe, inform your doctor. In the unlikely event you have an allergic reaction to this drug, seek medical attention immediately. Symptoms of an allergic reaction include: rash, itching, swelling, dizziness, trouble breathing. If you notice other effects not listed above, contact your doctor or pharmacist.


Tell your doctor your medical history especially if you have: kidney disease, anemia, any drug allergies. Caution is advised when using this drug in the elderly because they may be more sensitive to the effects of the drug. Trimethoprim should be used during pregnancy only if clearly needed. Discuss the risks and benefits with your doctor. This drug is excreted into breast milk and may have an effect on the nursing infant. Consult your doctor before breast-feeding.

Drug Interactions

Before using this drug tell your doctor of all drugs you may use, both prescription and nonprescription, especially: methotrexate, phenytoin, procainamide, dapsone, any other antibiotics. This drug may interfere with the effectiveness of birth control pills. Discuss using other methods of birth control with your doctor. Do not start or stop any medicine without doctor or pharmacist approval.


If overdose is suspected, contact your local poison control center or emergency room immediately. Symptoms of overdose may include nausea, vomiting, headaches, dizziness, depression, sore throat, fever, unusual bleeding or bruising, and confusion.


This medication has been prescribed for your current condition only. Do not use it later for another infection or give it to someone else. A different medication may be necessary in those cases.

Missed Dose

If you miss a dose, take as soon as remembered. If, however, it is almost time for the next dose and the dose is 1 daily, take the missed dose and the next dose 12 hours apart. If the dose is 2 daily, take the missed dose and the next dose 6 hours apart. Do not "double-up" the dose to catch up.


Store at room temperature away from moisture and sunlight. Do not store in the bathroom.