Adults

Varies significantly by indication. For amoebiasis: 400-800 mg three times daily for 5-10 days. For giardiasis: 2000 mg once daily for 3 days or 250 mg three times daily for 5-7 days. For anaerobic infections: 400 mg three times daily for 7 days. Children's dosage for suspension is typically 15-50 mg/kg/day divided into 3 doses, depending on the infection.

Elderly

No specific dose reduction required, but use with caution due to potential decreased hepatic function.

Renal_impairment

No dosage adjustment needed for mild to moderate renal impairment. For severe renal impairment or in patients undergoing dialysis, dose reduction (e.g., 50% of usual dose) may be necessary.

Onset

Varies by indication, generally effective within 1-2 days for most infections.

Excretion

Excreted mainly in the urine (60-80%), with a smaller amount excreted in the feces (6-15%).

Half life

Approximately 6-12 hours in adults, slightly longer in neonates and patients with severe hepatic impairment.

Absorption

Rapidly and well absorbed from the gastrointestinal tract after oral administration. Peak plasma concentrations are reached within 1-2 hours.

Metabolism

Primarily metabolized in the liver by oxidation (hydroxylation and glucuronidation) to active and inactive metabolites.

Alcohol

Disulfiram-like reaction (nausea, vomiting, flushing, tachycardia, headache, abdominal cramps) when consumed with or shortly after metronidazole. Avoid alcohol during and for at least 48 hours after treatment.

Lithium

Increases plasma lithium levels, potentially leading to lithium toxicity. Monitor lithium levels closely.

Cimetidine

May prolong metronidazole half-life, leading to increased plasma levels and potential toxicity.

Phenytoin, Phenobarbital

May decrease metronidazole plasma levels, reducing its efficacy.

Warfarin and other oral anticoagulants

Metronidazole can potentiate the anticoagulant effect, increasing the risk of bleeding. Close monitoring of INR and dose adjustment may be required.