Methoxsalen: Price, Dosage & Where to Buy

Methoxsalen is a psoralen medicine used with controlled long-wave ultraviolet A radiation in photochemotherapy. Its principal labelled use is the symptomatic control of severe, recalcitrant, disabling psoriasis that has not responded adequately to other treatment. It requires a prescription in the United Kingdom, and a generic version has been available since 2014-06-05.

Methoxsalen is indicated for the symptomatic control of severe, recalcitrant, disabling psoriasis that has not responded adequately to other forms of therapy and where the diagnosis has been supported by biopsy. It is intended to be used only together with a schedule of controlled doses of long-wave ultraviolet A radiation.

This treatment is restricted to severe disease and requires specialist assessment, because the medicine increases sensitivity to ultraviolet radiation. Methoxsalen is not labelled as a standalone treatment for psoriasis and should be used within supervised photochemotherapy.

The label lists soft gelatin oral capsules containing 10 mg of methoxsalen. The label lists administration with some low-fat food or milk before controlled ultraviolet A exposure. The usual starting dose is determined by body weight and by the specialist photochemotherapy protocol.

The label lists assessment of the minimum phototoxic dose and the phototoxic peak time before treatment begins. The usual starting dose is adjusted only by the treating physician when clinical assessment indicates that this is necessary. The label lists ultraviolet A exposure based on skin characteristics, with the exposure level determined by the physician.

The usual starting dose and exposure schedule are guidelines requiring individual evaluation, and treatment must not occur more often than once every other day. Any dosage increase is a specialist decision after treatment review.

Methoxsalen belongs to the psoralen group. It increases the skin's sensitivity to long-wave ultraviolet A radiation. After exposure to ultraviolet A, methoxsalen can interact with genetic material in skin cells, producing photochemical effects that reduce excessive skin-cell activity and inflammation associated with psoriasis.

The medicine therefore works as part of photochemotherapy rather than as an independent treatment. Because the same light-sensitising action can injure the skin and eyes, treatment requires carefully controlled ultraviolet exposure, specialist supervision and protective measures.

Animal reproduction studies have not been conducted with methoxsalen. It is not known whether methoxsalen can cause fetal harm when administered to a pregnant woman or affect reproductive capacity.

The label states that methoxsalen should be given to a woman with reproductive capacity only if clearly needed. Pregnancy or breastfeeding should be discussed with a doctor or pharmacist before treatment.

A missed dose may affect the planned relationship between methoxsalen and the supervised ultraviolet A session. The treatment schedule is determined by the physician and should not be changed independently.

A further dose should not be doubled or paired with an unscheduled ultraviolet exposure. Contact the prescribing phototherapy clinic or pharmacist for advice, particularly because phototoxic reactions may become evident later and treatments should not occur more often than once every other day.

Store at 20 °C to 25 °C, with excursions permitted between 15 °C and 30 °C. Keep the capsules in the amber-coloured glass bottle and protect them from unsuitable heat, light and moisture. Keep out of the reach of children and store as directed on the label to maintain quality.