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Trimethoprim Side Effects

Medically reviewed by Drugs.com. Last updated on Apr 24, 2024.

Applies to trimethoprim: oral solution, oral tablet.

Serious side effects of trimethoprim

Along with its needed effects, trimethoprim may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking trimethoprim:

Less common side effects

  • skin rash or itching

Rare side effects

  • black, tarry stools
  • blood in urine or stools
  • bluish fingernails, lips, or skin
  • changes in facial skin color
  • chills
  • difficult breathing or shortness of breath
  • fever with or without chills
  • general feeling of discomfort or illness
  • headache
  • joint or muscle pain
  • nausea
  • neck stiffness
  • pale skin
  • pinpoint red spots on skin
  • redness, blistering, burning, tenderness, peeling, or loosening of skin or mucous membranes
  • redness, swelling, or soreness of tongue
  • red skin lesions, often with a purple center
  • sore throat
  • swelling
  • thickened or scaly skin
  • unusual bleeding or bruising
  • unusual tiredness or weakness

Other side effects of trimethoprim

Some side effects of trimethoprim may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Less common side effects

  • diarrhea
  • loss of appetite
  • nausea or vomiting
  • stomach cramps or pain

For healthcare professionals

Applies to trimethoprim: compounding powder, oral solution, oral tablet.

General adverse events

The most common side effects were pruritus, rash, and mild gastrointestinal disturbances (including nausea, vomiting, glossitis); these effects were generally mild and reversed quickly when the drug was stopped.[Ref]

Metabolic

Hyperkalemia has been reported, particularly in elderly patients and patients with HIV.[Ref]

Dermatologic

Rash was generally mild to moderate and appeared 7 to 14 days after starting therapy.[Ref]

Gastrointestinal

Nervous system

Aseptic meningitis reversed rapidly when this drug was stopped but recurred in a number of cases upon re-exposure to sulfamethoxazole-trimethoprim or this drug alone.[Ref]

Other

Hematologic

Fatalities have been reported (especially in elder patients or patients with renal or liver dysfunction), but most hematological changes were mild and reversed when therapy was stopped.[Ref]

Hepatic

Fatalities have been reported with cholestatic jaundice and hepatic necrosis.[Ref]

Hypersensitivity

Psychiatric

Respiratory

Musculoskeletal

Renal

Whether increased BUN and serum creatinine were due to inhibition of creatinine tubular secretion or genuine renal dysfunction was not established.[Ref]

Genitourinary

Immunologic

Ocular

References

1. Cerner Multum, Inc. "UK Summary of Product Characteristics."

2. Cerner Multum, Inc. "Australian Product Information."

3. (2016) "Product Information. Trimethoprim (trimethoprim)." Teva Pharmaceuticals USA

Frequently asked questions

Further information

Trimethoprim side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.