The first successful treatment with methoxsalen was documented in 1948. By the 1950s this agent was an established medicine in many markets. It has been sold in the United States for decades under the brand name Oxsoralen, manufactured by Valeant Pharmaceuticals (formerly known as ICN Pharmaceuticals). The drug is FDA approved 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.
How is Supplied
Methoxsalen is most commonly supplied in regular or rapid-release capsules of 10 mg. It is also commonly supplied as a cream for topical application.
Structural Characteristics of Oxsoralen
Methoxsalen is a photoactive substance belonging to a class of compounds known as psoralens. It has the chemical designation 9-methoxy-7H-furo [3,2-g]  benzopyran-7-one.
Oxsoralen Warnings (Heightened sensitivity to light)
Psoralen drugs do not protect the skin from sun damage. These drugs increase the skin's sensitivity to sunlight, and can increase the likelihood of skin damage, skin aging, and skin cancer. Medical professionals do not prescribe psoralens for cosmetic purposes (tanning) due to these potential risks.
Oxsoralen Warnings (Ocular damage)
Psoralen drugs can increase susceptibility to ocular damage and cataracts. Goggles with complete UVA blocking properties must be worn at all times during light exposure therapy, and for 24 hours following exposure. The medical use of psoralens drugs does not appear to increase the rate of cataract formation when proper eye protection is used.
Oxsoralen Side Effects
The most common adverse reactions to methoxsalen therapy include nausea and severe itching, which occur in approximately 10% of patients. Reddening of the skin (erythema) is also common, and is an inflammatory reaction distinct from normal sunburn. Other adverse reactions include nausea, nervousness, insomnia, depression, edema, dizziness, headache, malaise, pigmentation irregularities, cyst, blister, rash, herpes simplex, prickly heat, inflammation of the hair follicles, gastrointestinal disturbances, skin touch sensitivity, leg cramps, low blood pressure, and exacerbated psoriasis.
When used medically to control severe psoriasis, methoxsalen is administered in conjunction with scheduled and controlled doses of long wave ultraviolet radiation. The dosage of methoxsalen is determined by bodyweight, and will range from 10 mg to 70 mg per application. UV exposure levels are determined after consideration of skin type and individual responsiveness to sun exposure. Therapy is usually initiated with drug and UV exposure commencing 2-3 times per week (clearing phase), followed by a schedule of once every 1 to 3 weeks (maintenance phase).
Methoxsalen is taken with a low fat meal or milk prior to UV exposure. Exposure is scheduled around the time of peak photosensitivity. Time of peak photosensitivity following administration is 1.5 to 2.1 hours with rapid-release capsules (Oxsoralen-Ultra), and 3.9 to 4.25 hours for regular methoxsalen capsules. The patient is instructed not to sunbathe 24 hours before and 48 hours after each dose of methoxsalen, and to avoid all sun exposure (even through clouds or glass) for 8 hours after each dose. The patient also must wear eyewear with full UVA protection for 24 hours following each application to protect the eyes from cataracts.
Oxsoralen Dosage (by weight)
When used (off-label) for cosmetic (tanning) purposes, the drug is usually initiated at a low dosage (10 mg), which will be slowly worked upwards by no more than 10 mg each application. The maximum dose will never exceed the recommended medical dose for a given bodyweight. As with medical use, UV light exposure is scheduled approximately 2 to 4 hours after administration of regular capsules, or 1.5 to 2 hours for rapid release capsules. The amount of time spent exposed to UV light (usually a normal tanning bed) is also increased slowly, starting with very brief intervals, as the user becomes accustomed to the drug. In an effort to have better control over skin tone and reduce the likelihood of burns or injury, each application period is typically separated by several days or more of drug abstinence.
Methoxsalen is available in more than 30 countries. The most common brand name is Oxsoralen from Valeant, although a number of other trade and generic forms can be located. This drug is not a common target of drug counterfeiting operations.
Wlliam Llewellyn (2017) - Anabolics