Trimethoprim
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From MedlinePlus, U.S. National Library of Medicine
Dihydrofolate Reductase Inhibitor Antibacterial
Dosing in kidney impairment
DOSAGE AND ADMINISTRATION The usual oral adult dosage is 100 mg of trimethoprim every 12 hours or 200 mg of trimethoprim every 24 hours, each for 10 days. The use of trimethoprim in patients with a creatinine clearance of less than 15 mL/min is not recommended. For patients with a creatinine clearance of 15 to 30 mL/min, the dose should be 50 mg every 12 hours.
Drug interactions
Check trimethoprim against a medication listLabel text (1 paragraph)
Drug Interactions Trimethoprim may inhibit the hepatic metabolism of phenytoin. Trimethoprim, given at a common clinical dosage, increased the phenytoin half-life by 51% and decreased the phenytoin metabolic clearance rate by 30%. When administering these drugs concurrently, one should be alert for possible excessive phenytoin effect.
Contraindications
Trimethoprim is contraindicated in individuals hypersensitive to trimethoprim and in those with documented megaloblastic anemia due to folate deficiency.
Safety data
Reported adverse events (FAERS)
Liver injury (LiverTox)
LiverTox has no chapter for trimethoprim. Check the label's hepatic warnings.
Pregnancy and lactation
Pregnancy
Pregnancy Teratogenic Effects Trimethoprim has been shown to be teratogenic in the rat when given in doses 40 times the human dose. In some rabbit studies, the overall increase in fetal loss (dead and resorbed and malformed conceptuses) was associated with doses six times the human therapeutic dose. While there are no large, well-controlled studies on the use of trimethoprim in pregnant women, Brumfitt and Pursell, 1 in a retrospective study, reported the outcome of 186 pregnancies during which the mother received either placebo or trimethoprim in combination with sulfamethoxazole.
The incidence of congenital abnormalities was 4.5% (3 of 66) in those who received placebo and 3.3% (4 of 120) in those receiving trimethoprim and sulfamethoxazole. There were no abnormalities in the 10 children whose mothers received the drug during the first trimester. In a separate survey, Brumfitt and Pursell also found no congenital abnormalities in 35 children whose mothers had received trimethoprim and sulfamethoxazole at the time of conception or shortly thereafter. Because trimethoprim may interfere with folic acid metabolism, trimethoprim should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
Nonteratogenic Effects The oral administration of trimethoprim to rats at a dose of 70 mg/kg/day commencing with the last third of gestation and continuing through parturition and lactation caused no deleterious effects on gestation or pup growth and survival.
Lactation
Nursing Mothers Trimethoprim is excreted in human milk. Because trimethoprim may interfere with folic acid metabolism, caution should be exercised when trimethoprim is administered to a nursing woman.
Breastfeeding (LactMed)
Because of the low levels of trimethoprim in breastmilk, amounts ingested by the infant are small and would not be expected to cause any adverse effects in breastfed infants.
Supply and cost
Drug shortage status
Recalls (last 24 months)
Therapeutic equivalence (Orange Book)
Price ladder
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