How Do Psoralens Work?

Psoralens are chemicals found in certain plants which make the skin temporarily sensitive to long-wave ultraviolet radiation (UVA). These are used to treat psoriasis and several other skin disorders.

PUVA or photochemotherapy is a combination of treatment that consists of taking psoralens orally (makes skin more sensitive to UV light) and then exposing the skin to UVA.

Psoralens boost the amount of ultraviolet light that the skin absorbs. Once the light energy is absorbed, these psoralens are energized to interact with DNA. This slows down the overgrowth of skin cells (inhibiting cell multiplication), which results in clearing up the psoriasis skin plaques. PUVA is effective in 80% of patients with psoriasis.

PUVA treatment is carried out in the following way:

• Light treatment is given two to three times per week for 12 to 15 weeks. It is never given on two consecutive days.
• For oral PUVA, psoralen capsules are taken 2 hours before the appointment for treatment (the amount of psoralen is based on the weight of the patient).
• Bath PUVA therapy involves the immersion of the entire body in psoralen solution followed by exposure to UVA. During treatment, the patient usually stands in a cabinet containing UVA fluorescent bulbs. The length of the exposure depends on the degree of the patient's pigmentation, the darker the patient, the longer the exposure time. During treatment, the patient needs to wear goggles to protect the eyes and to cover the face and groin to prevent burns.

Skin conditions treated with psoralens include the following:

• Psoriasis (a skin disease that causes red, itchy, scaly patches, most commonly on the knees, elbows, trunk, and scalp)
• Vitiligo (a disease that causes loss of skin color in patches)
• Eczema (a condition wherein patches of skin become inflamed, itchy, cracked, and rough)
• Alopecia (a condition that causes hair to fall out in small patches)
• Dermatitis (usually involves itchy, dry skin or a rash on swollen, reddened skin)
• Cutaneous T-cell lymphoma (a rare type of cancer that begins in white blood cells called T cells)
• Polymorphic light eruption (common skin rash triggered by exposure to sunlight or artificial ultraviolet light)
• Graft versus host disease (a potentially serious complication of allogeneic stem cell transplantation)
• Systemic sclerosis (an autoimmune inflammatory condition characterized by degenerative changes and scarring in the skin, joints, and internal organs)
• Cardiac allograft rejection (organ recipient's immune system recognizing a transplanted organ as foreign and mounting a response)

Common side effects include:

• Sunburn and blistering
• Nausea
• Vomiting
• Itching
• Skin rash
• Burning and/or stinging
• Redness
• Tanning or darkening of the skin

Other rare side effects include:

• Cataracts (clouding of the normally clear lens of the eye)
• Keratitis (an inflammatory condition that affects the cornea of the eye. The cornea is the clear part that covers both the iris and pupil)
• Headache
• Dizziness (feeling faint, weak, or unsteady)
• Skin cancer (melanoma, squamous cell carcinoma)
• Premature aging (dry skin and wrinkles)
• Discoloration of skin
• Lentigines (lesions that occur on the sun-exposed areas of the body, also called liver spots)
• Liver problems
• Allergic reactions:
• Hives
• Itching
• Swelling
• Malaise (a sense of unease or lack of well-being)

Information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with other medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.

Drug names include:                           

• 8MOP
• Methoxsalen
• Oxsoralen
• Oxsoralen ultra
• Uvadex