imiquimod

Imiquimod is a topical medication that acts as an immune response modifier. It is a small molecule agonist of toll-like receptor 7 (TLR7). Activation of TLR7 in skin cells stimulates innate and adaptive immune pathways, leading to production of cytokines such as interferon-α, interleukin-12, and tumor necrosis factor-α, which help clear virus-infected and malignant cells.

Imiquimod is approved in many countries for actinic keratosis (a precancerous skin lesion), superficial basal cell carcinoma, and external genital warts (condyloma acuminatum). It is formulated as a cream, commonly in 3.75% or 5% strengths, and is applied to the affected area according to regional labeling. Dosing schedules vary by indication and product; treatment typically continues for several weeks. The cream should be applied to dry, intact skin and not to mucous membranes; wash hands before and after application.

Adverse effects are mainly local skin reactions at the application site, including redness, itching, burning, pain, crusting, and erosion. Less common systemic effects may include fever or malaise. Cautions include avoiding use on broken skin, eyes, or mucous membranes, and use in pregnancy or breastfeeding should be discussed with a clinician. Monitoring by a clinician is advised to assess response and tolerability and to manage any inflammatory skin reactions that arise during therapy.

Brand names include Aldara and Zyclara. Imiquimod was approved by regulatory authorities in the late 1990s for genital warts and later for actinic keratosis and superficial basal cell carcinoma.