Metvix (Methyl Aminolevulinate)

Metvix (methyl aminolevulinate) is employed in photodynamic therapy for precancerous skin lesions, primarily actinic keratosis.

• Face actinic keratosis: reduces dysplastic lesions and lowers risk of progression to squamous cell carcinoma.
• Scalp actinic keratosis: clears lesions on the scalp and improves skin appearance.
• Field cancerization: treats areas of sun‑damaged skin with multiple subclinical lesions to prevent future tumor development.
• Other sun‑exposed sites: offers selective removal of dysplastic cells on areas such as the forearms and hands.

• Methyl aminolevulinate is a prodrug that penetrates keratinocytes and is metabolized within the heme biosynthetic pathway to protoporphyrin IX. Upon illumination with red light (approximately 630 nm), protoporphyrin IX generates reactive oxygen species that cause localized oxidative damage, leading to selective cytotoxicity of dysplastic epidermal cells while sparing surrounding healthy tissue. The reaction is confined to the illuminated area, providing precise control over the treatment field and minimizing systemic exposure.

Topical photodynamic therapy with Metvix may be associated with a range of skin reactions, most of which are localized and transient.

Common Side Effects

• Erythema: redness of the treated area lasting several days.
• Edema: mild swelling around the application site.
• Crusting: formation of a dry scab as the lesion resolves.
• Pain or burning: transient discomfort during or after illumination.
• Itching: mild pruritus in the treated region.
• Photosensitivity: increased sensitivity to light for a short period.

Serious or Rare Side Effects

• Severe allergic reaction: hives, swelling, or anaphylaxis requiring medical attention.
• Persistent ulceration: non‑healing sores that may become infected.
• Scarring: permanent tissue damage at the treatment site.
• Systemic phototoxicity: widespread skin reaction after extensive light exposure.
• Vision changes: rare ocular irritation if light reaches the eyes.

Before using Metvix, clinicians should observe several safety measures to reduce adverse reactions and ensure optimal efficacy.

• Avoid sun exposure: protect the treated area from daylight and artificial UV sources for at least 48 hours after illumination.
• Use approved light source: illumination must follow the recommended wavelength, intensity and duration specified in the product label.
• Assess skin condition: ensure the application site is free of active infection, open wounds or severe inflammation.
• Pregnancy and lactation: avoid use because safety has not been established in pregnant or nursing women.
• Apply to intact skin only: do not apply on mucous membranes, broken skin or areas with extensive dermatitis.
• Store at room temperature: keep the cream below 25 °C in the original container, protect from light and moisture.

Metvix can interact with other agents that affect photosensitivity or skin integrity, requiring careful management.

Major Interactions (Avoid)

• Systemic photosensitizing drugs: concurrent use (e.g., tetracyclines, sulfonamides) may amplify phototoxic reactions.
• Topical retinoids applied simultaneously: may increase local irritation and erythema.

Moderate Interactions (Monitor Closely)

• Other topical chemotherapeutic agents: monitor for additive skin toxicity when combined with agents such as 5‑fluorouracil.
• Oral anticoagulants: observe for prolonged bleeding if ulceration occurs at the treatment site.
• Immunosuppressive therapy: may reduce the efficacy of photodynamic treatment and require closer follow‑up.