A-Z Drug Facts > Metronidazole

Metronidazole

Pronouncation: (meh-troe-NID-uh-zole)
Class: Anti-infective agent, GI agent, Vaginal preparation

Trade Names:
Flagyl
- Tablets 250 mg
- Tablets 500 mg

Trade Names:
Flagyl ER
- Tablets, extended-release 750 mg

Trade Names:
Flagyl 375
- Capsules 375 mg

Trade Names:
Flagyl I.V.
- Powder for Injection, lyophilized 500 mg

Trade Names:
Flagyl I.V. RTU
- Injection 5 mg/mL

Trade Names:
Metric 21
- Tablets 250 mg

Trade Names:
MetroCream
- Cream 0.75%

Trade Names:
MetroGel
- Gel 0.75%

Trade Names:
MetroGel-Vaginal
- Gel 0.75%

Trade Names:
MetroLotion
- Lotion 0.75%

Trade Names:
Noritate
- Cream 1%

Trade Names:
Protostat
- Tablets 250 mg
- Tablets 500 mg

Apo-Metronidazole (Canada)
Florazole ER (Canada)
Nida Gel (Canada)
Novo-Nidazol (Canada)

Pharmacology

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

Pharmacokinetics

Absorption

Oral metronidazole is well absorbed; topical application is less complete and more prolonged. Following administration, T _max is 1 to 2 h, and C _max is 25 mg/mL. Oral bioavailability is not affected by food, but peak serum levels will be delayed to 2 h.

Distribution

Metronidazole appears in cerebrospinal fluid, saliva, and breast milk in concentrations similar to those found in plasma. Less than 20% is protein bound.

Metabolism

Metabolites are 2–hydroxymethyl and acidic metabolite.

Elimination

Routes of elimination are via urine (60% to 80%) and feces (6% to 15%). Renal Cl is approximately 10 mL/min per 1.73 m ² . The t _½ is 8 h in healthy adults, and the hydroxy-metabolite t _½ is 15 h.

Special Populations

Hepatic Function Impairment

Patients with hepatic function impairment metabolized metronidazole slower; accumulation of drug may occur. Cautiously administer doses below the usual recommended dose.

Elderly

Because the pharmacokinetics of metronidazole may be altered in the elderly, monitoring of serum levels may be necessary to adjust the dosage accordingly.

Indications and Usage

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 ( Flagyl ER only).

Topical

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

Vaginal

Treatment of bacterial vaginosis.

Unlabeled Uses

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

Contraindications

Hypersensitivity to nitroimidazole derivatives or any component of the products; first trimester of pregnancy in patients with trichomoniasis.

Dosage and Administration

Amebiasis
Adults

PO

Flagyl 375 capsules

Acute amebic dysentery and amebic liver abscess: 750 mg 3 time daily for 5 to 10 days.

Flagyl 250 mg tablets

Acute amebic dysentery: 750 mg 3 times daily for 5 to 10 days. Amebic liver abscess: 500 or 750 mg 3 times daily for 5 to 10 days.

Children

PO

Flagyl 375 , Flagyl 250 mg tablets

35 to 50 mg/kg per 24 h divided into 3 daily doses for 10 days.

Anaerobic Bacterial Infections

Give IV initially when treating most serious anaerobic infections.

Adults

IV 15 mg/kg loading dose infused over 1 h (approximately 1 g for a 70 kg adult); then a maintenance dose of 7.5 mg/kg infused over 1 h every 6 h (approximately 500 mg for a 70 kg adult). The first maintenance dose should be given 6 h following initiation of loading dose. Do not exceed 4 g in 24 h. May follow with similar oral dose. For prophylaxis, loading dose is to be completed 1 h before surgery, followed by maintenance dose 6 and 12 h later.

Duration

The usual duration is 7 to 10 days; however, infections of the bone, joint, lower respiratory tract, and endocardium may require longer treatment.

Adults

PO

Flagyl 375 , Flagyl 250 mg tablets

Usual dosage is 7.5 mg/kg (approximately 500 mg for a 70 kg adult) every 6 h (max, 4 g per 24 h) for 7 to 10 days; however, infections of the bone, joint, lower respiratory tract, and endocardium may require longer treatment.

Bacterial Vaginosis
Adults

PO 750 mg ( Flagyl ER ) daily for 7 consecutive days. Vaginal 1 applicator-full (approximately 37.5 mg metronidazole) intravaginally once or twice daily for 5 days; for daily dosing, administer at bedtime

Inflammatory Papules and Pustules of Rosacea
Adults

Topical Apply thin layer once daily (1% cream) or twice daily to entire affected areas after washing. Use morning and evening or as directed by health care provider. Avoid application close to eyes.

Trichomoniasis

Individualize treatment for women and men.

Adults

PO

Flagyl 375 capsules

Women: 375 mg twice daily for 7 consecutive days. When a repeat course is required, a lapse of 4 to 6 wk between courses is recommended.

Flagyl 250 mg tablets

250 mg 3 times daily for 7 consecutive days.

One-day treatment

2 g as a single dose or in 2 divided doses of 1 g each given on the same day.

Children

PO 5 mg/kg/dose 3 times daily for 7 days.

General Advice

• Injection
• Administer by IV infusion only. Not for intradermal, subcutaneous, or IM administration.
• Solution is administered directly from original IV container. No further dilution is required.
• Do not administer using equipment containing aluminum (eg, needles, cannulae) that may come in or make contact with drug solution.
• Administer prescribed dose over 30 to 60 min.
• Do not administer if particulate matter, cloudiness, or discoloration are noted or if the seals are not intact.
• Do not add other drugs to the metronidazole infusion bag.
• If other drugs are being administered through the same IV line, flush it before and after infusion of metronidazole. If being used with a primary IV fluid system, discontinue the primary solution during metronidazole infusion.
• Reconstituted Flagyl IV is stable for 96 h when stored above 86°F. Use diluted and neutralized IV solutions within 24 h.
• For proper reconstitution, dilution, and neutralization of IV solutions, see manufacturer's guidelines.

Storage/Stability

Store extended-release tablets, vaginal gel, topical cream, and topical gel at controlled room temperature (59° to 86°F). Store tablets, capsules, topical lotion, and injection below 77°F. Protect injection from light until use.

Drug Interactions

Anticoagulants

Anticoagulant effect may be increased.

Barbiturates, phenytoin

Therapeutic failure of metronidazole may occur.

Cimetidine

May prolong the t _½ and decrease plasma Cl of metronidazole.

Disulfiram

Concurrent use may result in acute psychosis or confusional state. Do not give metronidazole 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.

Lithium

Plasma levels may be elevated by metronidazole, increasing the risk of lithium toxicity.

Incompatibility

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

Laboratory Test Interactions

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

Adverse Reactions

When known, dose form and percentage are stated.

Cardiovascular

Flattening of T-wave.

CNS

Seizures; peripheral neuropathy; dizziness; vertigo; incoordination; ataxia; confusion; depression; insomnia; syncope; irritability; weakness.

Flagyl ER

Headache (18%); dizziness (4%).

MetroGel Vaginal

Headache (5%); dizziness (2%).

Dermatologic

Thrombophlebitis; urticaria; erythematous rash; flushing.

MetroGel Vaginal

Generalized itching or rash, skin irritation, transient skin erythema, mild skin dryness and burning (2%).

MetroLotion/Cream/Gel

Topical: erythema, local allergic reaction, contact dermatitis, pruritus, skin discomfort (burning, stinging), worsening of rosacea, dry skin, transient redness.

EENT

Metallic taste; glossitis; stomatitis.

Flagyl ER

Rhinitis (4%); sinusitis, pharyngitis (3%).

GI

Nausea; anorexia; vomiting; diarrhea; constipation; epigastric distress; cramps; pseudomembranous colitis; furry tongue; glossitis; stomatitis.

Flagyl ER

Nausea (10%); metallic taste (9%); abdominal pain, diarrhea (4%); dry mouth (2%).

MetroGel Vaginal

GI discomfort (7%); nausea, vomiting (4%); unusual taste (2%); diarrhea, loose stools, decreased appetite (1%).

Genitourinary

Darkening of urine; dysuria; cystitis; sense of pelvic pressure; polyuria; incontinence; vaginal Candida proliferation; decreased libido; proctitis.

Flagyl ER

Vaginitis (15%); genital pruritus (5%); abnormal urine, dysmenorrhea (3%); UTI (2%).

MetroGel Vaginal

Vaginal discharge (12%); symptomatic Candida cervicitis/vaginitis (10%); vulva/vaginal irritative symptoms (9%); pelvic discomfort (3%).

Hematologic

Mild leukopenia; reversible thrombocytopenia.

Respiratory

Flagyl ER

Upper respiratory tract infection (4%).

Miscellaneous

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 reactions. After prolonged IV use, thrombophlebitis may occur.

Flagyl ER

Bacterial infection (7%); influenza-like symptoms (6%); moniliasis (3%).

MetroGel Vaginal

Unspecified cramping (1%).

Precautions

Warnings Oral and IV metronidazole have been carcinogenic in mice and rats. Avoid unnecessary use.

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 Function

Patients with severe hepatic disease metabolize drug slowly; use caution and lower dose.

Candidiasis

Known or previously unrecognized candidiasis may present more prominent symptoms during therapy.

Hematologic effects

Use with caution in patients with a history of blood dyscrasia.

Neurologic effects

Seizures and peripheral neuropathy have occurred. Use extra caution with prolonged use, high doses, or history of CNS disease.

Overdosage

Symptoms

Nausea, vomiting, ataxia, seizures, peripheral neuropathy.

Patient Information

• Instruct patient to take exactly as prescribed and not to change dose or discontinue therapy unless advised by health care provider.
• Instruct patient to notify health care provider if infection does not appear to be improving or appears to be getting worse.
• Caution patient to avoid alcoholic beverages while taking metronidazole and for at least 3 days following completion of therapy.
• Advise patient that metallic taste is a common adverse reaction of therapy but that this will resolve when therapy has been discontinued.
• Advise patient to report any other bothersome adverse reactions to health care provider and to immediately report any abnormal neurologic signs or symptoms (eg, seizures, extremity numbness, abnormal skin sensations).

• Tablets and capsules
• Advise patient to take prescribed dose without regard to meals but to take with food if GI upset occurs.

• Extended-release tablets
• Advise patient to take prescribed dose daily, 1 h before or 2 h after a meal.
• Caution patient to swallow extended-release tablet whole and not crush, chew, or divide.

• Vaginal gel
• Review instructions for filling applicator, administering medication, and care of applicator.
• Advise patient that if accidental contact of the gel with the eye(s) occurs, to rinse the eye(s) with copious amounts of cool tap water. Advise patient to notify health care provider if eye irritation persists after rinsing.
• Advise patient to avoid vaginal intercourse during treatment.
• Advise patient to discontinue use and notify health care provider if vaginal irritation develops while using the medication.

• Topical
• Advise patient to cleanse areas to be treated before applying medication, then apply and rub in a thin film twice daily to entire affected areas.
• Advise patient that cosmetics may be applied after application of medication but if using lotion, to allow it to dry first.
• Advise patient that if local irritation occurs to apply the medication less frequently. If irritation persists, advise patient to discontinue use and notify health care provider.

• Injection
• Advise patient, family, or caregiver that medication will be prepared and administered by a health care provider in a health care setting.
• Advise patient to report injection-site pain or redness.

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