metronidazole hydrochloride
Pregnancy Risk Category B
How supplied
Tablets: 200 mg‡, 250 mg, 375 mg, 400 mg‡, 500 mg
Tablets (extended-release): 750 mg
Oral suspension (benzoyl metronidazole): 200 mg/5 ml‡
Injection: 500 mg/100 ml ready to use
Powder for injection: 500-mg single-dose vials
Action
A direct-acting trichomonacide and amebicide that works at both intestinal and extraintestinal sites. It is thought to enter the cells of microorganisms that contain nitroreductase. Unstable compounds are then formed that bind to DNA and inhibit synthesis, causing cell death.
Indications & dosage
Amoebic hepatic abscess-
Adults: 500 to 750 mg P.O. t.i.d. for 5 to 10 days.
Children: 30 to 50 mg/kg daily (in three divided doses) for 10 days.
Intestinal amebiasis-
Adults: 750 mg P.O. t.i.d. for 5 to 10 days.
Children: 30 to 50 mg/kg daily (in three divided doses) for 10 days.
Therapy for adults or children is followed by oral iodoquinol.
Trichomoniasis-
Adults: 250 mg P.O. t.i.d. for 7 days or 2 g P.O. in single dose (may give the 2-g dose in two 1-g doses, each on the same day); 4 to 6 weeks should elapse between courses of therapy.
Children: 5 mg/kg P.O. t.i.d. for 7 days.
Refractory trichomoniasis-
Adults: 250 mg P.O. b.i.d. for 10 days. Or, 500 mg P.O. b.i.d. for 7 days.
Bacterial infections due to anaerobic microorganisms-
Adults: loading dose is 15 mg/kg I.V. infused over 1 hour (about 1 g for a 70-kg [154-lb] adult). Maintenance dose is 7.5 mg/kg I.V. or P.O. q 6 hours (about 500 mg for a 70-kg adult). First maintenance dose should be given 6 hours after loading dose. Maximum dose not to exceed 4 g daily.
Prevention of postoperative infection in contaminated or potentially contaminated colorectal surgery-
Adults: 15 mg/kg I.V. infused over 30 to 60 minutes and completed about 1 hour before surgery. Then, 7.5 mg/kg I.V. infused over 30 to 60 minutes at 6 and 12 hours after initial dose.
Bacterial vaginosis-
Adults: 500 mg P.O. b.i.d. for 7 days.
Adverse reactions
CNS: vertigo, headache, ataxia, dizziness, syncope, incoordination, confusion, irritability, depression, weakness, insomnia, seizures, peripheral neuropathy.
CV: flattened T wave, edema.
EENT: rhinitis, sinusitis, pharyngitis, metallic taste.
GI: abdominal cramping or pain, stomatitis, epigastric distress, nausea, vomiting, anorexia, diarrhea, constipation, proctitis, dry mouth.
GU: darkened urine, polyuria, dysuria, cystitis, decreased libido, dyspareunia, dryness of vagina and vulva, vaginal candidiasis, vaginitis, genital pruritus.
Hematologic: transient leukopenia, neutropenia, thrombophlebitis after I.V. infusion.
Musculoskeletal: fleeting joint pains.
Respiratory: upper respiratory infection.
Skin: flushing, rash.
Other: fever, overgrowth of nonsusceptible organisms, especially Candida.
Interactions
Drug-drug. Cimetidine: increased risk of metronidazole toxicity because of inhibited hepatic metabolism. Monitor closely.
Disulfiram: acute psychoses and confusional states. Don't use within 2 weeks of last disulfiram dose.
Lithium: increased lithium levels resulting in possible toxicity. Monitor serum lithium levels closely.
Oral anticoagulants: increased anticoagulant effects. Monitor closely.
Phenobarbital, phenytoin: decreased metronidazole effectiveness. Total phenytoin clearance may be reduced. Monitor closely.
Drug-lifestyle. Alcohol use: disulfiram-like reaction (nausea, vomiting, headache, cramps, flushing). Don't use together or for 3 days after completion of drug therapy.
Effects on diagnostic tests
Metronidazole may interfere with the chemical analyses of aminotransferases and triglycerides, leading to falsely decreased values.
Contraindications
Contraindicated in patients with hypersensitivity to drug or other nitroimidazole derivatives and during the first trimester of pregnancy.
Nursing considerations
I.V. administration
Patient teaching
*Liquid contains alcohol. **May contain tartrazine. †Canada ‡Australia §U.K. OTCOver the counter
Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE-THREATENING