Metronidazole

metronidazole (me troe ni' da zole) Apo-Metronidazole (CAN), Flagyl, Flagyl 375, Flagyl ER, Flagyl IV, Flagyl IV RTU, MetroCream (CAN), MetroGel, Metro I.V., Neo-Tric (CAN), NidaGel (CAN), Noritate, Novonidazol (CAN), PMS-Metronidazole (CAN), Protostat, Trikacide (CAN) Pregnancy Category B Drug classes

Antibiotic Antibacterial Amebicide Antiprotozoal Therapeutic actions

Bactericidal: Inhibits DNA synthesis in specific (obligate) anaerobes, causing cell death; antiprotozoal-trichomonacidal, amebicidal: Biochemical mechanism of action is not known. Indications

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Acute infection with susceptible anaerobic bacteria Acute intestinal amebiasis Amebic liver abscess Trichomoniasis (acute and partners of patients with acute infection) Preoperative, intraoperative, postoperative prophylaxis for patients undergoing colorectal surgery Topical application: Treatment of inflammatory papules, pustules, and erythema of rosacea Unlabeled uses: Prophylaxis for patients undergoing gynecologic, abdominal surgery; hepatic encephalopathy; Crohn's disease; antibiotic-associated pseudomembranous colitis; treatment of Gardnerella vaginalis, giardiasis (use recommended by the CDC)

Contraindications and cautions

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Contraindicated with hypersensitivity to metronidazole; pregnancy (do not use for trichomoniasis in first trimester). Use cautiously with CNS diseases, hepatic disease, candidiasis (moniliasis), blood dyscrasias, lactation.

Available forms

Tablets—250, 500 mg; ER tablets—750 mg; capsules—375 mg; powder for injection— 500 mg; injection—500 mg/100 mL Dosages ADULTS

Oral

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Amebiasis: 750 mg/tid PO for 5–10 days. (In amebic dysentery, combine with iodoquinol 650 mg PO tid for 20 days.) Antibiotic-associated pseudomembranous colitis: 1–2 g/day PO for 7–10 days. Gardnerella vaginalis: 500 mg bid PO for 7 days. Giardiasis: 250 mg tid PO for 7 days. Trichomoniasis: 2 g PO in 1 day (1-day treatment) or 250 mg tid PO for 7 days.

IV

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Anaerobic bacterial infection: 15 mg/kg IV infused over 1 hr; then 7.5 mg/kg infused over 1 hr q 6 hr for 7–10 days, not to exceed 4 g/day. Prophylaxis: 15 mg/kg infused IV over 30–60 min and completed about 1 hr before surgery. Then 7.5 mg/kg infused over 30–60 min at 6- to 12-hr intervals after initial dose during the day of surgery only.

Topical (MetroGel)

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Treatment of inflammatory papules, pustules, and erythema of rosacea: Apply and rub in a thin film twice daily, morning and evening, to entire affected areas after washing; results should be seen within 3 wk; treatment through 9 wk has been effective.

PEDIATRIC PATIENTS

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Anaerobic bacterial infection: Not recommended. Amebiasis: 35–50 mg/kg/day PO in 3 doses for 10 days.

Pharmacokinetics Route Oral IV Topical

Onset Varies Rapid Generally no systemic absorption

Peak 1–2 hr 1–2 hr

Metabolism: Hepatic; T1/2: 6–8 hr Distribution: Crosses placenta; enters breast milk Excretion: Urine and feces IV facts

Preparation: Reconstitute by adding 4.4 mL of sterile water for injection, bacteriostatic water for injection, 0.9% sodium chloride injection, bacteriostatic 0.9% sodium chloride injection to the vial and mix thoroughly. Resultant volume is 5 mL with a concentration of 100 mg/mL. Solution should be clear to pale yellow to yellow-green; do not use if cloudy or if containing precipitates; use within 24 hr; protect from light. Add reconstituted solution to glass or plastic container containing 0.9% sodium chloride injection, 5% dextrose injection or lactated Ringer's; discontinue other solutions while running metronidazole. Infusion: Prior to administration, add 5 mEq sodium bicarbonate injection for each 500 mg used (if not using premixed bags); mix thoroughly. Do not refrigerate neutralized solution. Do not administer solution that has not been neutralized. Infuse over 1 hr. Adverse effects

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CNS: Headache, dizziness, ataxia, vertigo, incoordination, insomnia, seizures, peripheral neuropathy, fatigue GI: Unpleasant metallic taste, anorexia, nausea, vomiting, diarrhea, GI upset, cramps GU: Dysuria, incontinence, darkening of the urine Local: Thrombophlebitis (IV); redness, burning, dryness, and skin irritation (topical) Other: Severe, disulfiram-like interaction with alcohol, candidiasis (superinfection)

Interactions

Drug-drug • Decreased effectiveness with barbiturates • Disulfiram-like reaction (flushing, tachycardia, nausea, vomiting) with alcohol • Psychosis if taken with disulfiram • Increased bleeding tendencies with oral anticoagulants Drug-lab test • Falsely low (or zero) values in AST, ALT, LDH, triglycerides, hexokinase glucose tests Nursing considerations Assessment

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History: CNS or hepatic disease; candidiasis (moniliasis); blood dyscrasias; pregnancy; lactation Physical: Reflexes, affect; skin lesions, color (with topical application); abdominal exam, liver palpation; urinalysis, CBC, liver function tests

Interventions

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Avoid use unless necessary. Metronidazole is carcinogenic in some rodents. Administer oral doses with food. Apply topically (MetroGel, MetroCream) after cleansing the area. Advise patient that cosmetics may be used over the area after application. Reduce dosage in hepatic disease.

Teaching points

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Take full course of drug therapy; take the drug with food if GI upset occurs. Do not drink alcohol (beverages or preparations containing alcohol, cough syrups); severe reactions may occur. Your urine may appear dark; this is expected. Refrain from sexual intercourse unless partner wears a condom during treatment for trichomoniasis. Apply the topical preparation by cleansing the area and then rubbing a thin film into the affected area. Avoid contact with the eyes. Cosmetics may be applied to the area after application.

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These side effects may occur: Dry mouth with strange metallic taste (use frequent mouth care, suck sugarless candy); nausea, vomiting, diarrhea (eat frequent small meals). Report severe GI upset, dizziness, unusual fatigue or weakness, fever, chills.

Adverse effects in Italic are most common; those in Bold are life-threatening.