Trimethoprim Side Effects Center

Last updated on RxList: 3/1/2021
Trimethoprim Side Effects Center

What Is Trimethoprim?

Trimethoprim [Brand names: Trimpex (Discontinued Brand), Proloprim (Discontinued Brand), Primsol] is an antibiotic used to treat bacterial infections. Trimethoprim is often combined in a single pill with sulfamethoxazole. Trimethoprim is available in generic form.

What Are Side Effects of Trimethoprim?

Common side effects of trimethoprim include:

Dosage for Trimethoprim

The usual oral adult dosage of Trimethoprim is 100 mg every 12 hours or 200 mg trimethoprim every 24 hours, each for 10 days.

What Drugs, Substances, or Supplements Interact with Trimethoprim?

Trimethoprim may interact with dofetilide, digoxin, methotrexate, phenytoin, procainamide, and it may decrease the effectiveness of hormonal birth control. Tell your doctor all medications you are taking.

Trimethoprim During Pregnancy and Breastfeeding

Trimethoprim should be used only when prescribed during pregnancy. Trimethoprim passes into breast milk. While there have been no reports of harm to nursing infants, consult your doctor before breastfeeding.

Additional Information

Our Trimethoprim Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

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.


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Trimethoprim Professional Information


The adverse effects encountered most often with trimethoprim (trimethoprim (trimethoprim tablet) tablet) were rash and pruritus.


Rash, pruritus, and phototoxic skin eruptions. At the recommended dosage regimens of 100 mg b.i.d. or 200 mg q.d. each for 10 days, the incidence of rash is 2.9% to 6.7%. In clinical studies which employed high doses of trimethoprim (trimethoprim (trimethoprim tablet) tablet) , an elevated incidence of rash was noted. These rashes were maculopapular, morbilliform, pruritic, and generally mild to moderate, appearing 7 to 14 days after the initiation of therapy.


Rare reports of exfoliative dermatitis, erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis (Lyell Syndrome), and anaphylaxis have been received.


Epigastric distress, nausea, vomiting, and glossitis. Elevation of serum transaminase and bilirubin has been noted, but the significance of this finding is unknown. Cholestatic jaundice has been rarely reported.


Thrombocytopenia, leukopenia, neutropenia, megaloblastic anemia, and methemoglobinemia.


Hyperkalemia, hyponatremia.


Aseptic meningitis has been rarely reported.


Fever, and increases in BUN and serum creatinine levels.

Read the entire FDA prescribing information for Trimethoprim (Trimethoprim Tablet)


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© Trimethoprim Patient Information is supplied by Cerner Multum, Inc. and Trimethoprim Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

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