metronidazole

metronidazole

(me troe ni' da zole)

Apo-Metronidazole (CAN), Flagyl, Flagyl 375, Flagyl ER, Flagyl IV, Flagyl IV RTU, MetroGel, MetroGel-Vaginal, NidaGel (CAN),Noritate, Protostat

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

·        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-associatedpseudomembranous colitis; treatment of Gardnerella vaginalis, giardiasis (use recommended by the CDC)

Contraindications and cautions

·        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; lotion, cream, gel—0.75%; cream—1%; vaginal gel—0.75%

Dosages

ADULTS

Oral

·        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

·        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)

·        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.

Vaginal (MetroGel-Vaginal)

·        In non-pregnant women: 1 applicatorful intravaginally one to two times/day for 5 days.

PEDIATRIC PATIENTS

·        Anaerobic bacterial infection: Not recommended.

·        Amebiasis: 35–50 mg/kg/day PO in three doses for 10 days.

Pharmacokinetics

Route	Onset	Peak
Oral	Varies	1–2 hr
IV	Rapid	1–2 hr

Metabolism: Hepatic; T_1/2: 6–8 hr

Distribution: Crosses placenta; enters breast milk

Excretion: Feces, urine

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: Before 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

·        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

·        History: CNS or hepatic disease; candidiasis (moniliasis); blood dyscrasias; pregnancy; lactation

·        Physical: Reflexes, affect; skin lesions, color (with topical application); abdominal examination, liver palpation; urinalysis, CBC, LFTs

Interventions

·        WARNING: Avoid use unless necessary. Metronidazole is carcinogenic in some rodents.

·        Administer oral doses with food.

·        Apply topically (MetroGel) after cleansing the area. Advise patient that cosmetics may be used over the area after application.

·        Reduce dosage in hepatic disease.

Teaching points

·        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 during treatment for trichomoniasis unless partner wears a condom.

·        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.

·        You may experience these side effects: Dry mouth with strange metallic taste (frequent mouth care, sucking sugarless candies may help); 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.