Adult: 100 or 200 mg bid, alternatively, 200 or 300 mg once daily for 3-14 days, depending on severity. Child: 4 mth to 12 yr 6 mg/kg daily in 2 divided doses. Alternative regimen: 4 mth to 2 yr 25 mg bid; >2-6 yr 50 mg bid; >6-12 yr 100 mg bid.
Oral Prophylaxis of recurrent urinary tract infections
Adult: 100 mg once daily at night. Child: 4 mth to 12 yr 2 mg/kg once daily at night. Alternative regimen: 4 mth to 2 yr 25 mg at night; >2-8 yr 50 mg at night; >8-12 yr 100 mg at night.
Monitor CBC w/ differential, platelet count, liver enzyme, bilirubin, serum K, serum creatinine, and BUN periodically during prolonged therapy.
Symptoms: Nausea, vomiting, dizziness, headache, mental depression, confusion, bone marrow depression (e.g. thrombocytopenia, leucopenia, megaloblastic anaemia). Management: Symptomatic and supportive treatment. May employ gastric lavage and forced diuresis. Enhance elimination through urine acidification. May administer Ca folinate (5-15 mg daily) if bone marrow depression occurs.
May increase concentration of dapsone. Increased elimination and shortened elimination half-life w/ rifampicin. Increases concentration of phenytoin, digoxin, procainamide, rosiglitazone, repaglinide, zidovudine, zalcitabine, lamivudine. Increased risk of nephrotoxicity w/ ciclosporin. Potentiates anticoagulant effect of warfarin. May cause hyponatraemia w/ diuretics. May cause megaloblastic anaemia w/ other folate inhibitors (e.g. pyrimethamine, methotrexate). May increase potential for bone marrow aplasia w/ bone barrow depressants. Increased risk of hyperkalaemia w/ ACE inhibitors.
Interferes w/ serum methotrexate assay when used as binding protein for competitive binding protein technique (CBPA). May cause falsely elevated creatinine values w/ Jaffe alkaline picrate reaction assay.
Description: Trimethoprim, a diaminopyrimidine, is a reversible inhibitor of dihydrofolate reductase. It inhibits the conversion of bacterial dihydrofolic acid to tetrahydrofolic acid necessary for the synthesis of nucleic acids and proteins. It is either bacteriostatic or bacteriocidal, acting on the same metabolic pathway as sulfonamides. Pharmacokinetics: Absorption: Rapidly and extensively absorbed from the GI tract. Time to peak plasma concentration: 1-4 hr. Distribution: Widely distributed into body tissues and fluids. Readily crosses the placenta and enters breast milk. Volume of distribution: Approx 1.3 L/kg. Plasma protein binding: Approx 45%. Metabolism: Partially metabolised (10-20%) in the liver via demethylation, oxidation, and hydroxylation. Excretion: Via urine (approx 40-60%, mainly as unchanged drug) and faeces (small amounts). Elimination half-life: 8-10 hr.
J01EA01 - trimethoprim ; Belongs to the class of trimethoprim and derivatives. Used in the systemic treatment of infections.
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