metronidazole (topical)
MetroCream, MetroGel, MetroGel-Vaginal, MetroLotion, Nidagel ◆, Noritate

Available forms
Available by prescription only
Topical cream: 0.75%, 1%
Topical gel: 0.75%, 1%
Topical lotion: 0.75%
Vaginal gel: 0.75%

Indications and dosages
 Topical treatment of acne rosacea, pressure ulcer, inflammatory papules or pustules. Adults: Apply a thin film b.i.d. to affected area during the morning and evening (once daily for Noritate 1% topical gel). Significant results should be seen within 3 weeks and continue for first 9 weeks of therapy.
 Topical treatment of bacterial vaginosis. Adults: One applicatorful once daily or b.i.d., vaginally, for 5 days or once h.s. (nonpregnant women). In low-risk pregnant women, one applicatorful vaginally b.i.d. for 5 days.
 Treatment of pressure ulcer ◇. Adults: Prepare a 1% aqueous solution or suspension from crushed metronidazole tablets (sterilized); apply t.i.d.

Pharmacodynamics
Anti-inflammatory action: Although its exact mechanism of action is unknown, topical metronidazole probably exerts an anti-inflammatory effect through its antibacterial and antiprotozoal actions by affecting neutrophil function.

Pharmacokinetics
Absorption: Under normal conditions, serum levels of metronidazole after topical administration are negligible.
Distribution: Less than 20% bound to plasma proteins.
Metabolism: Unknown.
Excretion: Unknown after topical or intravaginal application.

Contraindications and precautions
Contraindicated in patients hypersensitive to drug, its ingredients (such as parabens), or other nitroimidazole derivatives. Use cautiously in patients with history of blood dyscrasia. Use vaginal form cautiously in patients with history of CNS disease because risk of seizures or peripheral neuropathy exists.

Interactions
Drug-drug. Oral anticoagulants: May potentiate anticoagulant effect. Monitor patient closely for adverse effects.
Drug-lifestyle. Alcohol use: May cause disulfiram-like reaction. Discourage alcohol use with vaginal form.

Adverse reactions
CNS: dizziness, light-headedness, headache (with vaginal form).
EENT: lacrimation (if topical gel is applied around the eyes).
GI: decreased appetite, cramps, pain, nausea, diarrhea, constipation, metallic or unpleasant taste sensation (with vaginal form).
GU: cervicitis, vaginitis, urinary frequency (with vaginal form).
Skin: rash, transient redness, dryness, mild burning, stinging.
Other: overgrowth of nonsusceptible organisms (with vaginal form).

Effects on lab test results
None reported.

Overdose and treatment
No information available. Overdose after topical application is unlikely.

Special considerations
• Topical metronidazole therapy hasn’t been linked to the adverse reactions observed with parenteral or oral metronidazole therapy. However, some of the drug can be absorbed following topical use. Limited clinical experience hasn’t shown any of these adverse effects.
• Vaginal metronidazole has limited reports of systemic-type reactions.
Breast-feeding patients
• Drug appears in breast milk. A decision should be made whether to discontinue drug or breast-feeding, after assessing the importance of drug to the woman.
Pediatric patients
• Safety hasn’t been established in children.

Patient education
• Advise patient to clean area thoroughly before applying drug. Patient may use cosmetics after applying drug.
• Instruct patient to avoid use of drug on eyelids and to apply it cautiously if drug must be used around the eyes.
• If local reactions occur, advise patient to apply drug less frequently or to discontinue use and call for specific instructions.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use