Vitilen

It is indicated for the repigmentation of idiopathic vitiligo. It is also indicated for the symptomatic control of severe, recalcitrant, disabling psoriasis not adequately responsive to other forms of therapy and when the diagnosis has been supported by biopsy.

The combination treatment regimen of Psoralen (P) and UVA (Ultraviolet radiation of 320-400 nm wavelength) is commonly known as PUVA. Skin reactivity to UVA radiation is enhanced by the ingestion of Methoxsalen. The drug reaches its maximum bioavailability 1-3 hours after oral administration and may last for up to 8 hours. Methoxsalen is reversibly bound to serum albumin and is also preferentially taken up by epidermal cells. In both mice and man, Methoxsalen is rapidly metabolized. Approximately 95% of the drug is excreted as a series of metabolites in the urine within 24 hours.

The exact mechanism of action of Methoxsalen with the epidermal melanocytes and keratinocytes is not known. The best known biochemical reaction of Methoxsalen is with DNA. Methoxsalen, upon photoactivation, conjugates and forms covalent bonds with DNA (both monofunctional and bifunctional). Reactions with proteins have also been described.

May increase plasma concentration of drugs metabolised by CYP2A6 isoenzyme. Additive effect with other systemic or topical photosensitising agents (e.g. anthralin, coal tar, nalidixic acid).

The most commonly reported side effect of Methoxsalen alone is nausea, which occurs with approximately 10% of all patients. This effect may be minimized or avoided by instructing the patient to take Methoxsalen with milk or food, or to divide the dose into two portions, taken approximately one-half hour apart. Other effects include nervousness, insomnia and psychological depression.

Pregnancy Category C. Methoxsalen should be given to a woman only if clearly needed. It is not known whether this drug is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when Methoxsalen is administered to a nursing woman.

Skin burning: Serious burns from either UVA or sunlight (even through window glass) can result if the recommended dosage of the drug and/or exposure schedules are not maintained.

Carcinogenicity: The increasing risk of carcinoma appears great among patients who are fair skinned or had pre PUVA exposure or prolong treatment with tar UVB, ionizing radiation or arsenic.

Cataractogenicity: Among patients using proper eye protection, there is no evidence for a significantly increased risk of cataracts in association with PUVA therapy.

Patients must not sunbathe during the 24 hours prior to Methoxsalen ingestion and UV exposure.

Pediatric use: Safety in children has not been established.

Methoxsalen preparation

In the event of Methoxsalen overdosage, induce emesis and keep the patient in a darkened room for at least 24 hours. Emesis is beneficial only within the first 2 to 3 hours after ingestion of Methoxsalen, since maximum blood levels are reached by this time.

Store at 25°C; excursions permitted to 15°C-30°C.