Metrosa (Metronidazole)

Metrosa is used in dermatology to target bacterial and inflammatory pathways involved in specific skin disorders.

• Rosacea: improves facial redness, papules and pustules by reducing the proliferation of skin‑associated anaerobic bacteria and modulating inflammatory mediators.
• Acne vulgaris: helps clear inflammatory lesions and decreases the number of Propionibacterium‑acnes colonies, leading to reduced papules, pustules and overall lesion count.
• Skin bacterial overgrowth: may be employed to control localized anaerobic bacterial colonisation in certain dermatologic conditions.

• Metronidazole enters susceptible microorganisms and undergoes intracellular reduction of its nitro group by electron‑transport proteins. The reduced intermediate binds to DNA, causing strand breakage and inhibition of nucleic acid synthesis, which leads to cell death. In the skin, this antimicrobial effect reduces the load of anaerobic bacteria and diminishes the significant inflammatory response that contributes to rosacea and acne lesions.

Metrosa may cause local skin reactions and, rarely, systemic adverse events.

Common Side Effects

• Skin irritation: mild burning, stinging or tingling sensation at the application site, usually transient.
• Redness: transient erythema or mild flushing around the treated area, often resolving without intervention.
• Dryness: peeling, flaking or slight scaling of the skin where the product is applied.

Serious or Rare Side Effects

• Allergic reaction: hives, swelling, severe rash or angioedema indicating hypersensitivity.
• Stevens‑Johnson syndrome: rare severe reaction with extensive skin blistering, mucosal involvement and systemic symptoms.
• Anaphylaxis: life‑threatening systemic hypersensitivity that may include airway compromise, requiring emergency care.

When using Metrosa, consider the following precautions to ensure safe and effective therapy.

• Hypersensitivity: avoid use in patients with known allergy to metronidazole or other nitroimidazoles.
• Extensive skin damage: do not apply on large open wounds, burns or compromised skin barrier.
• Pregnancy: use only if the potential benefit outweighs the risk, as safety data are limited.
• Pediatric use: not recommended for children unless specifically prescribed by a qualified clinician.
• Concomitant alcohol: advise patients to limit alcohol intake, as systemic absorption may cause a disulfiram‑like reaction.
• Store at below 25°C: keep the product in its original container, protect from moisture and direct sunlight.

Metrosa may interact with certain systemic medications and substances; monitor the following interactions.

Major Interactions (Avoid)

• Oral metronidazole: concurrent use can increase systemic exposure and risk of toxicity.
• Alcohol consumption: may precipitate a disulfiram‑like reaction causing flushing, nausea and tachycardia.
• Warfarin: topical use may enhance anticoagulant effect, increasing bleeding risk.

Moderate Interactions (Monitor Closely)

• Lithium: systemic absorption may raise lithium levels, requiring serum monitoring.
• Cytochrome P450 inducers (e.g., rifampicin): may reduce metronidazole efficacy if absorbed.
• Other topical antibiotics: combined use may increase local irritation.