Metronidazole

  Action Enters bacterial or protozoal cell and impairs synthesis of DNA, resulting in cell death.

  Indications Treatment of serious infections caused by susceptible anaerobic bacteria; prophylaxis of postoperative infection in patients undergoing colorectal surgery; treatment of amebiasis; treatment of trichomoniasis and asymptomatic partners of infected patients; bacterial vaginosis.

Topical: Treatment of inflammatory papules, pustules, and erythema of acne rosacea.

Vaginal: Treatment of bacterial vaginosis.

Treatment of hepatic encephalopathy, Crohn disease, antibiotic-associated pseudomembranous colitis, Helicobacter pylori infections.

  Contraindications Hypersensitivity to nitroimidazole derivatives; first trimester of pregnancy in patients with trichomoniasis.

  Route/Dosage

Anaerobic Bacterial Infections

ADULTS: IV 15 mg/kg loading dose infused over 1 hr (approximately 1 g for a 70 kg adult); then 7.5 mg/kg infused over 1 hr q 6 hr (approximately 500 mg for a 70-mg adult). Do not exceed 4 g in 24 hr. May follow with similar oral dose. For prophylaxis, loading dose is to be completed 1 hr before surgery, followed by maintenance dose 6 and 12 hr later.

Bacterial Vaginosis

ADULTS: PO 750 mg (Flagyl ER) once daily for 7 consecutive days. Vaginal 1 applicatorful (approximately 37.5 mg metronidazole) intravaginally bid for 5 days.

  Interactions

Anticoagulants: Anticoagulant effect may be increased.

Barbiturates: Therapeutic failure of metronidazole may occur.

Disulfiram: Concurrent use may result in acute psychosis or confusional state. Metronidazole should not be given to patients who have taken disulfiram within last 2 wk.

Ethanol: Disulfiram-like reaction including flushing, palpitations, tachycardia, nausea, and vomiting may occur with concurrent use.

Do not use aluminum-containing equipment with metronidazole because solution will turn orange/rust color.

  Lab Test Interferences May interfere with chemical analyses for AST, ALT, LDH, triglycerides, and hexokinase glucose; zero values may occur.

  Adverse Reactions

CARDIOVASCULAR: Flattening of T-wave. CNS: Seizures; peripheral neuropathy; dizziness; vertigo; incoordination; ataxia; confusion; depression; insomnia; syncope. DERMATOLOGIC: Thrombophlebitis; urticaria; erythematous rash; flushing. EENT: Metallic taste; glossitis; stomatitis. GI: Nausea; anorexia; vomiting; diarrhea; epigastric distress; cramps; proctitis; pseudomembranous colitis. GU: Darkening of urine; dysuria; cystitis; polyuria; incontinence; vaginal Candida proliferation; decreased libido. HEMATOLOGIC: Mild leukopenia. OTHER: Hypersensitivity reactions including dermatologic reactions, nasal congestion, dry mouth or vagina, and fever; fleeting joint pain; pancreatitis. Topical or vaginal use may cause similar adverse effects. After prolonged IV use, thrombophlebitis may occur.

  Precautions

Pregnancy: Category B. Lactation: Excreted in breast milk. Children: Safety and efficacy not established, except for amebiasis. Elderly: Monitoring serum levels may be necessary for proper dosing. Hepatic Impairment: Patients with severe hepatic disease metabolize drug slowly; use caution and lower dose. Neurologic Effects: Seizures and peripheral neuropathy have occurred. Use extra caution with prolonged use, high doses, or history of CNS disease.

  Administration/Storage

• Add 4.4 mL of Sterile Water for Injection, bacteriostatic water, or sterile saline solution to vial to reconstitute medication.
• Add solution to either D5W, 0.9% normal saline or Lactated Ringer’s solution; do not exceed concentration of 8 mg/mL.
• Neutralize IV solution with 5 mEq sodium bicarbonate for each 500 mL of solution.
• Monitor IV infusion for slow continuous or intermittent drip only. If administered by intermittent infusion, discontinue primary fluid during infusion.
• Use IV metronidazole cautiously in patients on sodium-restricted diet. Each gram contains 28 mEq of sodium.
• Do not use equipment containing aluminum.
• Clean treatment area prior to topical applications.
• Apply topical applications in thin film each morning and evening for 9-wk course of therapy. Wash hands before and after application. Avoid contact with eyes.
• Store reconstituted solution at 30°F in room light; reconstituted solutions are stable for 96 hr.
• Use neutralized solutions within 24 hr.
• Prior to reconstitution, store less than 86°F. Protect from light.

  Assessment/Interventions

• Obtain patient history, including drug history and any known allergies.
• Assess blood levels of medication when used in pediatric and geriatric patients.
• Observe for therapeutic results, which may take 3 wk to occur.
• Notify health care provider if patient experiences numbness or paresthesia of extremities, seizures, or GI distress.
• Observe for psychotic reactions in alcoholic patients.

  Patient/Family Education

• Instruct patient to crush tablet if difficult to swallow whole.
• Tell patient not to engage in vaginal intercourse during treatment with vaginal cream.
• Discuss current drug therapies (anticoagulants, disulfiram) with health care provider, and explain any specific precautions.
• Tell patient to wash hands before and after application of topical or vaginal creams and to avoid eye contact.
• Explain that cosmetics may be applied over topical metronidazole.
• Advise patient that oral medications can be taken with food to decrease GI upset.
• Inform patient that medication may cause darkening of urine or metallic taste in mouth.
• Instruct patient to refrain from sexual intercourse during treatment for trichomoniasis.
• Explain that the patient’s sexual partner should undergo evaluation and treatment by health care provider.
• Tell patient that mineral oil base in vaginal cream may weaken latex or rubber products such as condom or diaphragm and should not be used for 72 hr after treatment is completed.
• Explain that vaginal cream should be inserted high into the vagina.
• Instruct patient to avoid intake of alcoholic beverages for greater than or equal to 1 full day after therapy is stopped.