Brand names: MetroCream, MetroGel, MetroGel-Vaginal, MetroLotion, Noritate, Vandazole
Drug class: Antibacterials

Medically reviewed by Drugs.com on Oct 10, 2024. Written by ASHP.

Introduction

Antibacterial and antiprotozoal; also has anti-inflammatory and immunosuppressive effects; nitroimidazole derivative.

Uses for metroNIDAZOLE (Topical)

Rosacea

Treatment of inflammatory lesions (papules and pustules) associated with rosacea (acne rosacea); topical gel designated an orphan drug by FDA for use in this condition.

Has no beneficial effects on telangiectasia, rhinophyma, or ocular manifestations of rosacea.

Optimal treatment not determined; inflammatory lesions may respond to long-term treatment with topical anti-infectives (e.g., metronidazole) or oral anti-infectives (e.g., doxycycline, tetracycline, erythromycin, ampicillin, metronidazole). Topical metronidazole may be preferred to oral metronidazole; has been effective in patients with inadequate response or relapse with other therapies (e.g., oral tetracycline).

Effects appear palliative; manifestations recur commonly following discontinuance of therapy.

Adjunctive measures recommended to decrease exposure to factors that exacerbate rosacea (e.g., excessive sunlight, wind, hot liquids, spicy food, alcohol, extremes of heat and cold).

Bacterial Vaginosis

Treatment of bacterial vaginosis (formerly called Haemophilus vaginitis, Gardnerella vaginitis, nonspecific vaginitis, Corynebacterium vaginitis, anaerobic vaginosis) in nonpregnant women.

CDC recommends treatment of bacterial vaginosis in all symptomatic women (including pregnant women). In addition, asymptomatic pregnant women at high risk for complications of pregnancy should be screened (preferably at the first prenatal visit) and treatment initiated if needed.

Treatment recommendations for bacterial vaginosis in HIV-infected women are the same as those for women without HIV infection.

Regimens of choice in nonpregnant women are a 7-day regimen of oral metronidazole, a 5-day regimen of intravaginal metronidazole gel, or a 7-day regimen of intravaginal clindamycin cream; alternative regimens are a 7-day regimen of oral clindamycin or 3-day regimen of intravaginal clindamycin suppositories. The preferred regimens for pregnant women are a 7-day regimen of oral metronidazole or a 7-day regimen of oral clindamycin.

Regardless of regimen used, relapse or recurrence is common; an alternative regimen (e.g., oral therapy when topical was used initially) may be used in such situations.

Routine treatment of asymptomatic male sexual contacts of women who have relapsing or recurrent bacterial vaginosis not recommended.

Decubitus and Other Ulcers

Treatment of infected decubitus ulcers^{† [off-label]}; topical metronidazole designated an orphan drug by FDA for use in treatment of grade III or IV, anaerobically infected, decubitus ulcers.

Perioral Dermatitis

Treatment of perioral dermatitis^{† [off-label]}; topical gel designated an orphan drug by FDA for treatment of this condition.

Trichomoniasis

Has been used intravaginally as an adjunct to oral metronidazole for treatment of trichomoniasis caused by Trichomonas vaginalis ^{† [off-label]} in selected cases (e.g., refractory infections), but not included in CDC recommendations for treatment of trichomoniasis. Intravaginal metronidazole not effective used alone.

Drug of choice for treatment of trichomoniasis is oral metronidazole or oral tinidazole.

metroNIDAZOLE (Topical) Dosage and Administration

Administration

Administer topically to the skin or intravaginally in appropriate formulations.

Topical skin preparations (cream, gel, lotion) are for external use only and should not be used orally, intravaginally, or near or in eyes.

Intravaginal preparations are for intravaginal administration only and should not be used orally, topically on the skin, or near or in eyes.

Topical Administration

Apply topically to the skin as a 0.75 or 1% cream, 1% gel, or 0.75% lotion.

Prior to topical application, wash affected area with mild, nonirritating cleanser. To minimize risk of local irritation, some clinicians suggest application be delayed until about 15–20 minutes after skin cleansing.

Rub cream, gel, or lotion into affected area. Avoid contact with eyes.

If irritation occurs at application site, reduce application frequency or discontinue.

Cosmetics may be applied to skin after application of cream, gel, or lotion; allow lotion to dry ≥5 minutes before applying cosmetics.

Intravaginal Topical Administration

Administer intravaginally as a 0.75% gel using vaginal applicators provided by the manufacturers.

If once-daily regimen used, administer dose at bedtime.

If once-daily regimen used, use new vaginal applicator for each dose. If twice-daily regimen used, use new applicator each day; wash, rinse, and dry applicator after morning dose and discard after evening dose.

Dosage

Pediatric Patients

Bacterial Vaginosis

Treatment in Nonpregnant Postmenarchal Females

Intravaginal

0.75% gel: One applicatorful (approximately 37.5 mg of metronidazole) once daily (at bedtime) or twice daily (in morning and evening) given for 5 consecutive days.

Adults

Rosacea

Topical

0.75% cream or lotion: Apply thin film to cleansed, affected area twice daily (morning and evening) or as directed by clinician.

1% cream or gel: Apply thin film to cleansed, affected area once daily.

Optimum treatment duration not established; has been continued for ≥21 weeks in clinical studies.

Chronic therapy (usually intermittent) may be necessary, particularly for moderate to severe disease.

Clinical improvement usually occurs within 3 weeks. Once adequate response occurs, adjust frequency and duration of treatment according to disease course.

Although disease may remit during treatment, relapse occurs commonly following discontinuance.

Bacterial Vaginosis

Treatment in Nonpregnant Women

Intravaginal

0.75% gel: One applicatorful (approximately 37.5 mg of metronidazole) once daily (at bedtime) or twice daily (in morning and evening) given for 5 consecutive days.

Cautions for metroNIDAZOLE (Topical)

Contraindications

• Known hypersensitivity to metronidazole, other nitroimidazole derivatives, or any ingredient in the formulation.

Warnings/Precautions

Warnings

Seizures and Peripheral Neuropathy

Convulsive seizures and peripheral neuropathy (characterized by numbness or paresthesia of an extremity) reported with oral or IV nitroimidazoles (e.g., metronidazole, tinidazole).

If abnormal neurologic signs develop with vaginal gel, promptly discontinue drug.

Use vaginal gel with caution in patients with history of CNS disease.

Interactions

Psychotic reactions reported in alcoholic patients receiving oral metronidazole and disulfiram concurrently; disulfiram-like reactions to alcohol reported in patients receiving oral metronidazole. Similar reactions could occur with intravaginal metronidazole.

Avoid intravaginal metronidazole in patients who have received disulfiram within the last 2 weeks. Caution patients to avoid drinking alcohol while being treated with intravaginal metronidazole.

General Precautions

Administration Precautions

Avoid contact with the eyes.

Topical cream, gel, or lotion may cause tearing.

Vaginal gel may cause ocular burning and irritation.

Irrigate eyes with copious amounts of cool water if contact occurs.

Local Irritation

If reaction suggesting local irritation occurs, advise patient to use the topical preparation less frequently or discontinue use.

History of Blood Dyscrasia

Use with caution in patients with evidence or history of blood dyscrasia.

Transient leukopenia and neutropenia reported with systemic metronidazole; adverse hematologic abnormalities not reported to date with topical metronidazole.

Vaginal Intercourse and Use of Vaginal Products

Patients treated with vaginal gel should not engage in vaginal intercourse and should not use other vaginal products (tampons, douches) during entire treatment course.

Vaginal intercourse or other vaginal products could reduce efficacy of intravaginal metronidazole (e.g., by dislodgment and/or dilution, by increased vaginal pH secondary to deposition of semen).

Superinfection

Symptoms of known or previously unrecognized vaginal candidiasis may become more prominent during intravaginal metronidazole therapy. Symptomatic Candida vaginitis reported during or immediately after therapy.

Systemic Adverse Effects

Although topical application to skin results in lower systemic absorption than oral or IV administration, adverse systemic effects (e.g., metallic taste, nausea, paresthesia, tingling or numbness of extremities ) have been reported with topical metronidazole.

Although intravaginal administration results in lower systemic absorption than oral or IV administration, consider possibility that adverse effects reported with systemic metronidazole could occur when drug is given intravaginally.

Specific Populations

Pregnancy

Category B.

Safety and efficacy of intravaginal metronidazole for treatment of bacterial vaginosis in pregnant women not established. Existing data do not support use of intravaginal agents during pregnancy and intravaginal metronidazole not included in current CDC recommendations for treatment of bacterial vaginosis in pregnant women.

Lactation

Distributed into milk following oral or IV administration; not known whether distributed into milk following topical or intravaginal administration.

Discontinue nursing or the drug.

Pediatric Use

Safety and efficacy of topical or intravaginal metronidazole not established in pediatric patients.

One manufacturer states safety and efficacy of vaginal gel established in postmenarchal females based on extrapolation of data from adult women; safety and efficacy of vaginal gel not established in premenarchal females.

Geriatric Use

Safety and efficacy of topical gel in geriatric patients ≥65 years of age appear similar to those in younger adults.

Insufficient experience with vaginal gel in patients ≥65 years of age to determine whether geriatric patients respond differently than younger adults.

Hepatic Impairment

Use vaginal gel with caution in severe hepatic impairment.

Reduced elimination and increased plasma concentrations may occur in severe hepatic dysfunction.

Common Adverse Effects

Topical application to skin: Local effects such as erythema, irritation, stinging/burning, local allergic reactions, contact dermatitis, drying, pruritus, aggravated rosacea.

Intravaginal administration: Vaginal discharge, symptomatic Candida cervicitis/vaginitis, fungal infection, vulvovaginal irritation, dysmenorrhea, GI effects (abdominal pain, GI discomfort, nausea, vomiting, diarrhea), headache, pruritus.

Drug Interactions

Because metronidazole can be absorbed systemically following topical application to skin or following intravaginal administration, the possibility that drug and laboratory test interactions could occur with these routes should be considered.

Specific Drugs and Laboratory Tests

metroNIDAZOLE (Topical) Pharmacokinetics

Absorption

Bioavailability

Absorbed systemically following topical application to skin; extent of absorption depends on formulation used (cream, gel, lotion).

Absorbed systemically following intravaginal administration; systemic bioavailability of vaginal gel averages 50–56%.

Following repeated topical application to the face of 1% cream (approximately 3.75 mg per dose) in adults with rosacea, serum concentrations were minimal or undetectable. Following topical application to the face of 1 g of 1% cream in healthy individuals, serum concentrations were minimal or undetectable and peak serum concentrations were attained within 8–12 hours after the dose.

Following topical application to the face of 1 g of 1% topical gel in adults with rosacea, peak serum concentrations of metronidazole were attained 6–10 hours after the dose and were <1% of concentrations reported with a single 250-mg oral dose.

Following topical application to the face of 1 g of 0.75% topical lotion (approximately 7.5 mg of metronidazole) twice daily for 4 days, drug was detectable in plasma of all patients and peak plasma concentrations were approximately 80 times lower than peak concentrations attained with a single 250-mg oral dose.

Following intravaginal administration of 5 g of 0.75% vaginal gel (approximately 37.5 mg of metronidazole) in healthy women, peak serum concentrations were attained 4–17 hours after the dose and were approximately 2% of that attained after a single 500-mg oral dose.

Distribution

Extent

Not fully characterized following topical application to skin or intravaginal administration.

Crosses placenta following oral or IV administration; not known whether crosses placenta following topical application to skin or intravaginal administration.

Distributed into milk following oral or IV administration; not known whether distributed into milk following topical application to skin or intravaginal administration.

Elimination

Metabolism

Not fully characterized following topical application to skin or intravaginal administration.

Elimination Route

Any systemically absorbed drug probably metabolized in liver and excreted in urine.

Stability

Storage

Topical

Cream

20–25°C.

Gel

20–25°C (may be exposed to 15–30°C).

Lotion

20–25°C; do not freeze.

Intravaginal

Gel

MetroGel-Vaginal: 15–30°C; do not freeze.

Vandazole: 20–25°C; do not freeze.

Actions

• Bactericidal, amebicidal, and trichomonacidal in action.

• Un-ionized at physiologic pH and readily taken up by anaerobic organisms or cells. In susceptible organisms or cells, metronidazole reduced by low-redox-potential electron transport proteins (e.g., nitroreductases such as ferredoxin); the reduction product(s) apparently are responsible for cytotoxic and antimicrobial effects of the drug (e.g., disruption of DNA, inhibition of nucleic acid synthesis).

• Has direct anti-inflammatory effects and effects on neutrophil motility, lymphocyte transformation, and some aspects of cell-mediated immunity.

• Mechanism of reducing inflammatory lesions (papules and pustules) and erythema in patients with rosacea not elucidated to date; these effects may result from anti-inflammatory or immunosuppressive actions of the drug.

• Suppression of skin bacteria does not appear to play a major role in the mechanism of action of the drug in treatment of inflammatory lesions of rosacea; inactive in vitro against Propionibacterium acnes, staphylococci, and streptococci, and has no appreciable effects on the aerobic or anaerobic microflora of the skin of patients with rosacea.

• Spectrum of activity includes most obligately anaerobic bacteria and many protozoa. Inactive against fungi and viruses and most aerobic or facultatively anaerobic bacteria.

• Gram-positive anaerobes: Active against Clostridium, C. difficile, C. perfringens, Eubacterium, Peptococcus, and Peptostreptococcus. Actinomyces, Lactobacillus, Propionibacterium acnes, P. avidum, and P. granulosum generally are resistant.

  Gram-negative anaerobes: Active against Bacteroides fragilis, B. distasonis, B. ovatus, B. thetaiotaomicron, B. vulgatus, B. ureolyticus, Fusobacterium, Prevotella bivia, P. disiens, P. intermedia, P. melaninogenica, P. oralis, Porphyromonas, and Veillonella.

• Other organisms: Active against Campylobacter fetus. Most strains of Gardnerella vaginalis (formerly Haemophilus vaginalis) are susceptible only to relatively high concentrations in vitro. Concentrations readily achievable locally (750 mcg/mL) following intravaginal application of 0.75% vaginal gel have inhibited approximately 90% of strains tested in vitro.

• Natural and acquired resistance has been reported in some T. vaginalis. Resistance also reported rarely in B. fragilis and other anaerobic bacteria following long-term therapy.

Advice to Patients

• Importance of using topical or intravaginal metronidazole only as directed and only for the disorder for which drug was prescribed.

• Advise patients that topical cream, gel, and lotion are for external use only and to avoid contact with eyes.

• Advise patients that vaginal gel is for intravaginal administration only and to avoid contact with eyes. If such contact occurs, importance of irrigating eyes with copious amounts of cool water.

• Instruct patients receiving vaginal gel regarding appropriate use of vaginal applicator.

• Advise women using vaginal gel not to engage in vaginal intercourse and not to use other vaginal products (tampons, douches) during entire treatment course.

• Advise patients to avoid alcohol while using vaginal gel.

• Importance of notifying clinicians if local reactions or any other adverse reactions occur.

• Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs, as well as any concomitant illnesses.

• Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.

• Importance of informing patients of other important precautionary information.

Additional Information

The American Society of Health-System Pharmacists, Inc. represents that the information provided in the accompanying monograph was formulated with a reasonable standard of care, and in conformity with professional standards in the field. Readers are advised that decisions regarding use of drugs are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and that the information contained in the monograph is provided for informational purposes only. The manufacturer’s labeling should be consulted for more detailed information. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information contained in the monograph is not a substitute for medical care.

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

Reload page with references included

Medical Disclaimer