Indications: high activity against anaerobic bacteria and protozoa; surgical and gynaecological sepsis in which activity against colonic anaerobes especially Bacteroides fragilis is important, trichomonal vaginitis, non-specific vaginitis, and E.histolytica and Giardia lamblia infections.

Cautions: active CNS disease, disulfiram-like reaction with alcohol; hepatic impairment.

Side Effects: gastro-intestinal disturbances (including nausea and vomiting), taste disturbances, furred tongue, oral mucositis, anorexia; very rarely hepatitis, jaundice, pancreatitis, drowsiness, dizziness, headache, ataxia, psychotic disorders, darkening of urine, thrombocytopenia, pancytopenia, myalgia, arthralgia, visual disturbances, rash, pruritus, and erythema multiforme; on prolonged or intensive therapy peripheral neuropathy, transient epileptiform seizures, and leucopenia.

Dose: Anaerobic infections (usually treated for 7 days and for 10 days in antibiotic-associated colitis), ADULTS by mouth, either 800 mg initially then 400 mg every 8 hours or 500 mg every 8 hours, CHILD 7.5 mg/kg every 8 hours; by rectum, 1 g every 8 hours for 3 days, then 1 g every 12 hours, CHILD every 8 hours for 3 days, then every 12 hours, age up to 1 year 125 mg, 1–5 years 250 mg, 5–10 years 500 mg, over 10 years, adult dose;

by intravenous infusion over 20 minutes, 500 mg every 8 hours; CHILD 7.5 mg/kg every 8 hours;

Leg ulcers and pressure sores, by mouth, 400 mg every 8 hours for 7 days;

Bacterial vaginosis, by mouth, 400–500 mg twice daily for 5–7 days or 2 g as a single dose;

Pelvic inflammatory disease, by mouth, 400 mg twice daily for 14 days;

Acute ulcerative gingivitis, by mouth, 200–250 mg every 8 hours for 3 days;

CHILD 1–3 years 50 mg every 8 hours for 3 days;

3–7 years 100 mg every 12 hours;

7–10 years 100 mg every 8 hours.

Acute oral infections, by mouth, 200 mg every 8 hours for 3–7 days;

CHILD 1–3 years 50 mg every 8 hours for 3–7 days;

3–7 years 100 mg every 12 hours;

7–10 years 100 mg every 8 hours.

Surgical prophylaxis, by mouth, 400–500 mg 2 hours before surgery; up to 3 further doses of 400–500 mg may be given every 8 hours for high-risk procedures;

CHILD 7.5 mg/kg 2 hours before surgery; up to 3 further doses of 7.5 mg/kg may be given every 8 hours for high-risk procedures.

By rectum, 1 g 2 hours before surgery; up to 3 further doses of 1 g may be given every 8 hours for high-risk procedures; CHILD 5–10 years 500 mg 2 hours before surgery; up to 3 further doses of 500 mg may be given every 8 hours for high-risk procedures.

By intravenous infusion (if rectal administration inappropriate), 500 mg at induction; up to 3 further doses of 500 mg may be given every 8 hours for high-risk procedures; CHILD 7.5 mg/kg at induction; up to 3 further doses of 7.5 mg/kg may be given every 8 hours for high- risk procedures.