Trimethoprim

Trimethoprim

Approved uses

• INDICATIONS & USAGE To reduce the development of drug-resistant bacteria and maintain the effectiveness of trimethoprim tablets, USP and other antibacterial drugs, trimethoprim tablets, USP should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria.
• When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy.
• In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy.
• For the treatment of initial episodes of uncomplicated urinary tract infections due to susceptible strains of the following organisms: Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, Enterobacter species, and coagulase-negative Staphylococcus species, including S. saprophyticus.

Forms and strengths

• Trimethoprim tablets, USP, 100 mg: White, round, convex tablet, debossed "N", bisect, "L" on one side and debossed "330" on the other, in bottles of 100.

How it is taken

• DOSAGE & 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.

Must not be used when

• Trimethoprim is contraindicated in individuals hypersensitive to trimethoprim and in those with documented megaloblastic anemia due to folate deficiency.

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.

Warnings and precautions

• Serious hypersensitivity reactions have been reported rarely in patients on trimethoprim therapy.
• Trimethoprim has been reported rarely to interfere with hematopoiesis, especially when administered in large doses and/or for prolonged periods.
• The presence of clinical signs such as sore throat, fever, pallor, or purpura may be early indications of serious blood disorders (see OVERDOSAGE, Chronic).
• Complete blood counts should be obtained if any of these signs are noted in a patient receiving trimethoprim and the drug discontinued if a significant reduction in the count of any formed blood element is found.

Common side effects

• The adverse effects encountered most often with trimethoprim were rash and pruritus. Dermatologic Rash, pruritus, and phototoxic skin eruptions.

Pregnancy

Teratogenic Effects Pregnancy category C 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.

How it acts

Microbiology Mechanism of Action Trimethoprim blocks the production of tetrahydrofolic acid from dihydrofolic acid by binding to and reversibly inhibiting the required enzyme, dihydrofolate reductase. This binding is very much stronger for the bacterial enzyme than for the corresponding mammalian enzyme.

Label holder:

Lupin Pharmaceuticals,Inc.

Label version:

4 June 2024

This section reports the approved product information. The wording is condensed from the regulator's own summary, and the full document is linked under Sources.