Metroderme (Metronidazole)

Metronidazole is used topically to manage infections caused by anaerobic bacteria and certain protozoa.

• Rosacea: reduces inflammatory papules, pustules and persistent erythema.
• Bacterial vaginosis: eradicates anaerobic bacterial overgrowth in the vaginal flora.
• Perioral dermatitis: controls the bacterial component and improves skin appearance.

• Metronidazole penetrates microbial cells and undergoes reduction of its nitro group under anaerobic conditions. The reduced metabolites interact with DNA, causing strand breakage and loss of helical stability, which inhibits nucleic acid synthesis and leads to cell death of susceptible anaerobic bacteria and protozoa.

Topical application of Metroderme may cause local reactions, while systemic absorption can rarely produce serious events.

Common Side Effects

• Skin irritation: mild redness or discomfort at the application site.
• Burning or stinging sensation during or after use.
• Dryness or peeling of the treated skin.
• Itching or mild pruritus.
• Erythema: transient redness.
• Sensation of warmth.

Serious or Rare Side Effects

• Allergic reaction: hives, swelling, or difficulty breathing.
• Stevens‑Johnson syndrome or toxic epidermal necrolysis.
• Severe skin rash or bullous dermatitis.
• Photosensitivity leading to exaggerated sunburn.
• Anaphylaxis: rapid onset of systemic allergic response.
• Systemic toxicity: nausea, headache, or seizures (rare with extensive use).

When using Metroderme, consider the following safety measures.

• Hypersensitivity: avoid if the patient has known allergy to metronidazole or nitroimidazoles.
• Extensive skin damage: do not apply on large open wounds, burns, or ulcerated areas.
• Pregnancy and lactation: use only if the prescriber determines benefit outweighs risk.
• Alcohol consumption: advise patients to limit alcohol to reduce disulfiram‑like reactions.
• Concomitant medications: review for potential interactions before initiating therapy.
• Store at room temperature: keep in the original container, protect from moisture and light.

Metronidazole can interact with several systemic agents; monitoring is advised.

Major Interactions (Avoid)

• Alcohol: may cause severe flushing, nausea, and tachycardia.
• Warfarin: increased anticoagulant effect, risk of bleeding.
• Lithium: heightened lithium toxicity.
• Phenytoin: reduced efficacy of metronidazole.
• Cimetidine: elevated metronidazole plasma concentrations.

Moderate Interactions (Monitor Closely)

• Oral contraceptives: possible reduction in contraceptive effectiveness.
• Other antiepileptics (e.g., carbamazepine): enzyme induction may lower metronidazole levels.
• Rifampin: may decrease metronidazole exposure, reducing therapeutic effect.