Dr Agustin Alomar
Psoralens + UVA (PUVA) therapy is a well-known treatment for vitiligo, as well as Narrowband-UVB (NB-UVB), but other photochemotherapy regimens for vitiligo consists of khellin as a photosensitiser, a furanochromone extracted of the plant Amni visnaga (5,8 dimetoxi.2 methyl-4,5 furo-6,7 chromone), and UVA irradiation (KUVA). The main advantage is its lack of phototoxicity, making it safe for use either as a home treatment or a treatment involving natural sunlight, even on a daily regimen. It is also less mutagenic than psoralens, and lessens the darkening of normal skin. Khellin can be given orally at 100 mg, 2 hours before treatment. The efficacy rate of this treatment can be compared to PUVA, but is limited as approximately 30% of patients develop liver toxicity (cytolysis), resulting in oral systemic treatment being practically abandoned.
Khellin can also be formulated for topical applications, incorporated into a moisturising cream or carbopol gel, at a concentration of 3 to 5%. Sunlight irradiation in the form of topical ‘KUVA-sun’ could also be very useful in sunny countries where it is possible to receive low doses of natural sunlight over several months, with very nice results. However, its efficacy in comparison with oral PUVA or other therapeutic modalities has not been established.
Twenty years of experience have convinced me completely about the use of topically-applied khellin plus sunlight exposure. Although its capacity to stimulate melanocyte mitosis is inferior to psoralens, its long-term safety is important.
Topical application of khellin achieves a notable level of penetration of the active substance to the basal layer in just an hour (according to recent unpublished research), yet daily application also achieves an effective epidermic depot effect. The combination of a minimum daily sunlight exposure of 5, 10, or 15 minutes if possible, usually produces excellent results in responsive body areas.