Trimethoprim
Indications
Trimethoprim is used for:
Urinary tract infections, Gastroenteritis, Pneumocystis jiroveci pneumonia, Resp tract infections
Adult Dose
Oral
Respiratory tract infections; Gastroenteritis; Susceptible infections; Uncomplicated urinary tract infections
Adult: Acute infection: 100 or 200 mg twice daily, alternatively, 200 or 300 mg daily as a single dose may be used.
For initial UTI episodes: 100 mg every 12 hr or 200 mg every 24 hr for 10 days.
Intravenous
Respiratory tract infections; Gastroenteritis; Treatment and prophylaxis of urinary tract infections
Adult: 200 mg every 12 hr by Inj or infusion.
Child Dose
Oral
Respiratory tract infections; Gastroenteritis; Susceptible infections; Uncomplicated urinary tract infections
Child: 6-8 mg/kg/day in 2 divided doses.
Alternatively,
6 wk-5 mth: 25 mg bid,
6 mth-5 yr: 50 mg bid,
6-12 yr: 100 mg bid.
Intravenous
Respiratory tract infections; Gastroenteritis; Treatment and prophylaxis of urinary tract infections
Child: 8 mg/kg daily in 2-3 divided doses.
Renal Dose
Renal impairment:
CrCl (ml/min) Dosage Recommendation
15-27 Normal dose for 3 days, thereafter half the normal doses.
<15 Half the normal dose from the start of the treatment.
Administration
Should be taken with food.
Contra Indications
Hypersensitivity, serious haematological disorders, severe renal impairment, megaloblastic anaemia secondary to folate depletion.
Precautions
Renal and hepatic impairment, porphyria, patients with potential folate deficiency, elderly, pregnancy, lactation, children with fragile X chromosome associated with mental retardation. Perform regular haematological examination.
Pregnancy-Lactation
Pregnancy Category: C
Lactation: enters breast milk
Interactions
Concurrent use increased risk of blood dyscrasias with azathioprine, methotrexate, pyrimethamine; increased risk of hyperkalaemia with ACE inhibitors; increased risk of hyponatraemia when used with both potassium-sparing diuretics and thiazides; increased risk of bleeding with warfarin; increased risk of lithium toxicity; increased digoxin, phenytoin, procainamide, lamivudine, stavudine, repaglinide, rosiglitazone, dofetilide serum levels; decreased ciclosporin levels. Concurrent use with dapsone increased serum levels of both and increased risk of dapsone toxicity.
Adverse Effects
Side effects of Trimethoprim :
Nausea, vomiting, glossitis, pruritus, skin rash, fever, hyponatremia, hyperkalaemia, photosensitivity, liver enzyme elevation, , raised serum creatinine and BUN, blood dyscrasias, cholestatic jaundice, anaphylaxis, aseptic meningitis.
Potentially Fatal: Stevens-Johnson syndrome, toxic epidermal necrolysis.
Mechanism of Action
Trimethoprim inhibits the conversion of bacterial dihydrofolic acid to tetrahydrofolic acid which is important for the synthesis of DNA. It may be bacteriostatic or bactericidal depending on growth conditions. It is active against a wide range of gm-ve and gm+ve aerobes, as well as some protozoa.