Topical photochemotherapeutics

What are Topical photochemotherapeutics?

Topical photochemotherapeutics make your skin more sensitive to light. They work by causing a reaction with light that can destroy certain types of diseased skin cells. They may be used in the treatment of vitiligo or actinic keratosis in combination with light treatment.

In addition to phototherapy, photochemotherapy is widely used in the treatment of psoriasis. Photochemotherapy refers to the administration of a drug either topically or systemically that is photoactivated and becomes therapeutically effective. Although some agents become active when exposed to UVB, most have a spectrum that requires exposure to UVA. The most commonly used photochemotherapeutic agents for psoriasis are the psoralens. These are polycyclic compounds that become excited when exposed to UVA and form cycloadducts with pyrimidine bases. The most commonly used agent in the United States is 8-methoxypsoralen (8-MOP).

Twenty-two patients with alopecia areata were treated with a combination of topical 0.1% 8-methoxypsoralen and UVA (PUVA). Eight of the twenty-two patients (36.3%) responded with excellent regrowth (terminal hair in at least 75% of the treated scalp), and two patients (9.1%) showed good regrowth (terminal hair in 50% to 75% of the treated scalp).

The mean total UVA exposure and the mean total number of treatments for the entire treatment course for these responders was 171.7 joules/cm² and 47.4 treatments, respectively. Eight of the nine responders available for follow-up experienced some degree of relapse when PUVA treatments were tapered or during a follow-up period (mean, 8.3 months) after treatment was discontinued. Despite the failure of topical PUVA to change the long-term course of alopecia, the combination of PUVA with other therapeutic modalities may result in the prolongation of the beneficial effect in selected patients. The mechanism of action of PUVA in alopecia areata might involve an immunomodulatory effect.