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Trimethoprim Disease Interactions

There are 3 disease interactions with trimethoprim.


Trimethoprim (applies to trimethoprim) folate deficiency

Major Potential Hazard, High plausibility. Applicable conditions: Anemia Associated with Folate Deficiency, Folic Acid/Cyanocobalamin Deficiency, Renal Dysfunction, Hemolytic Anemia, Alcoholism, Malnourished

The use of trimethoprim is contraindicated in patients with documented megaloblastic anemia due to folate deficiency. Trimethoprim inhibits dihydrofolate reductase, an enzyme necessary in the synthesis of tetrahydrofolic acid, or the metabolically active form of folic acid. Thrombocytopenia, neutropenia, megaloblastic anemia, and methemoglobinemia have been reported rarely. However, the risk is increased in the presence of folate deficiency, chronic hemolytic anemia and/or renal impairment, as well as during prolonged therapy (e.g., > 6 months) with high dosages. Therapy with trimethoprim should be administered cautiously under these conditions and in patients with suspected folate depletion (e.g., elderly, alcoholic, malnourished or debilitated patients). Folic acid supplementation, if necessary, may be administered concomitantly without interfering with the antibacterial action of trimethoprim. Patients should be instructed to immediately report any signs or symptoms suggestive of hematologic toxicity such as fever, sore throat, local infection, bleeding, pallor, dizziness, or jaundice. Leucovorin (folinic acid) should be administered if bone marrow depression is detected.


  1. Chan M, Beale D, Moorhead J "Acute megaloblastosis due to cotrimoxazole." Br J Clin Pract 34 (1980): 87-8
  2. Sheehan J "Trimethoprim-associated marrow toxicity." Lancet 2 (1981): 692
  3. "Product Information. Trimpex (trimethoprim)." Roche Laboratories PROD (2001):
  4. "Product Information. Proloprim (trimethoprim)." Glaxo Wellcome PROD (2001):
View all 4 references

Trimethoprim (applies to trimethoprim) dialysis

Moderate Potential Hazard, High plausibility. Applicable conditions: hemodialysis

Trimethoprim is moderately removed by hemodialysis. Doses should either be scheduled for administration after dialysis or supplemental doses be given after dialysis.


  1. Patel RB, Welling PG "Clinical pharmacokinetics of co-trimoxazole (trimethoprim-sulphamethoxazole)." Clin Pharmacokinet 5 (1980): 405-23
  2. Nissenson AR, Wilson C, Holazo A "Pharmacokinetics of intravenous trimethoprim-sulfamethoxazole during hemodialysis." Am J Nephrol 7 (1987): 270-4
  3. "Product Information. Trimpex (trimethoprim)." Roche Laboratories PROD (2001):
  4. "Product Information. Proloprim (trimethoprim)." Glaxo Wellcome PROD (2001):
View all 4 references

Trimethoprim (applies to trimethoprim) renal dysfunction

Moderate Potential Hazard, High plausibility.

Trimethoprim is primarily eliminated by the kidney. The serum concentration of trimethoprim may be increased and the half-life prolonged in patients with impaired renal function. Dosage adjustments may be necessary and modifications should be based on the degree of renal impairment as well as severity of infection. The manufacturers recommend a dosage of 50 mg every 12 hours in patients with creatinine clearance between 15 to 30 mL/min and not using the drug in patients with creatinine clearance below 15 mL/min.


  1. Andreasen F, Elsborg L, Husted S, Thomsen O "Pharmacokinetics of sulfadiazine and trimethoprim in man." Eur J Clin Pharmacol 14 (1978): 57-67
  2. Bergan T, Brodwall E, Vik-Mo H, Anstad U "Pharmacokinetics of sulphadiazine, sulphamethoxazole and trimethoprim in patients with varying renal function." Infection 7 (1979): s382-7
  3. Adam WR, Henning M, Dawborn JK "Excretion of trimethoprim and sulphamethoxazole in patients with renal failure." Aust N Z J Med 3 (1973): 383-7
  4. Rieder J, Schwartz DE, Fernex M, et al. "Pharmacokinetics of the antibacterial combination sulfamethoxazole plus trimethoprim in patients with normal or impaired kidney function." Antibiot Chemother 18 (1974): 148-98
  5. Nolte H, Buttner H "Pharmacokinetics of trimethoprim and its combination with sulfamethoxazole in man after single and chronic oral administration." Chemotherapy 18 (1973): 274-84
  6. Bergan T, Brodwall EK "Kidney transport in man of sulfamethoxazole and trimethoprim." Chemotherapy 17 (1972): 320-33
  7. Odlind B, Hartvig P, Fjellstrom KE, Lindstrom B, Bengtsson S "Steady state pharmacokinetics of trimethoprim 300 mg once daily in healthy volunteers assessed by two independent methods." Eur J Clin Pharmacol 26 (1984): 393-7
  8. Ahlmen J, Brorson J-E "Pharmacokinetics of trimethoprim given in single daily doses for three days." Scand J Infect Dis 14 (1982): 143-5
  9. Hengstmann JH "Pharmacokinetics of trimethoprim and tetroxoprim: a review." Antibiot Chemother 31 (1982): 211-24
  10. Watson ID, Stewart MJ, Wiles A, McIntosh SJ "Pharmacokinetics of two dosage levels of trimethoprim to "steady-state" in normal volunteers." J Int Med Res 11 (1983): 137-44
  11. "Product Information. Trimpex (trimethoprim)." Roche Laboratories PROD (2001):
View all 11 references

Trimethoprim drug interactions

There are 131 drug interactions with trimethoprim.

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Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.