Adults

Amoebiasis: 400-800 mg three times daily for 5-10 days. Anaerobic infections: 400-500 mg every 8 hours. Dosage varies by indication and severity.

Elderly

Generally, no specific dosage adjustment is required unless there is significant hepatic impairment. Monitor for adverse effects.

Renal_impairment

In severe renal impairment (CrCl <10 mL/min), dose reduction (e.g., 50%) or extended dosing interval may be considered, but generally not required for mild to moderate impairment.

Onset

Therapeutic effects usually seen within days, depending on the infection type and severity.

Excretion

Mainly renal (60-80% as unchanged drug and metabolites); some fecal excretion (6-15%).

Half life

Approximately 8 hours (range: 6-12 hours) in adults.

Absorption

Rapidly and well absorbed after oral administration, with bioavailability typically greater than 80%.

Metabolism

Primarily hepatic (liver) via oxidation with side-chain hydroxylation and glucuronide conjugation.

Alcohol

Disulfiram-like reaction (nausea, vomiting, abdominal cramps, flushing, headache) when consumed during treatment and for at least 3 days after stopping metronidazole.

Lithium

May increase plasma lithium levels, leading to lithium toxicity. Monitor lithium levels.

Cimetidine

May prolong metronidazole half-life by inhibiting its metabolism, increasing plasma levels.

Phenytoin, Phenobarbital

May decrease metronidazole plasma levels by increasing its metabolism.

Warfarin and other oral anticoagulants

Potentiates anticoagulant effect, increasing risk of bleeding. Requires close INR monitoring and possible dose adjustment of anticoagulant.