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Medical and Pharmacy Editor:

Brand Name: Primsol, Proloprim, TMP

Generic Name: Trimethoprim

Drug Class: Antibiotics, Other

What Is Trimethoprim and How Does It Work?

Trimethoprim is an antibiotic used to treat bacterial infections. It works by stopping the growth of bacteria.

Trimethoprim treats only bacterial infections. It will not work for viral infections (e.g., common cold, flu). Unnecessary use or overuse of any antibiotic can lead to its decreased effectiveness.

Trimethoprim may also be used to treat some lung infections (Pneumocystis carinii pneumonia) and to prevent kidney infections in certain patients.

Trimethoprim is available under the following different brand names: Primsol, Proloprim, and TMP.

Dosages of Trimethoprim:

Dosage Forms and Strengths

Oral solution

  • 50 mg/5mL


  • 100 mg

Dosage Considerations – Should be Given as Follows:

Susceptible Infections

  • 100 mg orally every 12 hours

Renal Impairment

  • CrCl 15-30 mL/min: 50 mg every 12 hours
  • CrCl less than 15 mL/min: 100 mg every 24 hours or avoid use

Other Information

  • See also combo with sulfamethoxazole (Cotrim/Bactrim/Septra/Sulfatrim)
  • Available also as a combo with sulfadiazine (Coptin) in Canada

Other Indications and Uses

  • Urinary tract infection (UTI) caused by E. coli, Enterobacter spp., K. pneumoniae, P. mirabilis, coagulase-negative Staphylococcus spp
  • Pediatric: Children under 12 years old: safety and efficacy not established
Medically Reviewed by a Doctor on 6/15/2017

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