PUVA Treatment.
What is PUVA. PUVA is therapy with Psoralen and ultraviolet A rays. It is used in the treatment of psoriasis, eczema, vitiligo and some other skin conditions.
Like ultraviolet B, ultraviolet A is also present in sunlight. But UVA has a longer wave length than UVB and is ineffective when used alone. But when its use is combined with a photosensitive drug, it proves useful.
PUVA or Psoralen plus UVA (Ultraviolet A).
This is a specialized treatment which is also referred to as photochemotherapy as it combines treating psoriasis with phototherapy (here UVA is used and not UVB) and a photosensitization drug. The light sensitizing drug in PUVA is called psoralen.
Psoralen is given first before exposure to artificial UVA light. This is done because psoralen makes the skin psoriasis more responsive to UVA light, thereby allowing smaller doses of UVA to be required. UVA light is used instead of UVB because UVA light penetrates deeper into the skin than UVB. This makes this treatment more aggressive and effective and also the choice for more severe forms of psoriasis. PUVA treatment is seen to be most effective against stable plaque psoriasis, guttate psoriasis and psoriasis of the palms and feet.
Psoralen.
Psoralens are natural substances which are derived from plants like cellary. It is given as oral pills or either as a topical lotion or as a psoralen bath and after a short period the skin is exposed to UVA light. UVA is a special wavelength of light which is “weaker” than UVB.
As explained above, Psoralen is a photosensitive drug which makes the skin more responsive to UVA rays. This facilitates lower doses of UVA to be used.
Psoralen tablet is taken 2 hours before light therapy with UVA. Alternatively, topical Psoralen (Gel or cream) can be applied over the skin 30 minutes before UVA is given. An added option is to add Psoralen to the bath and soak in it for about 15 minutes.
Dosage of PUVA.
Treatment is given 2 or 3 times a week for a number of weeks which are decided by the attending practitioner. Doses of UVA light are administered in a physician’s office so that he or she can gradually increase the light exposure time with each session. The dose is determined by the physician after studying the psoriasis and its type. To determine the starting dose, the following is done:
After taking oral Psoralen by the patient, a small area of the skin is exposed to UVA. The dose that produces uniform redness of the skin after a period of 72 hours becomes the starting point of treatment. It is called the minimum phototoxic dose (MPD).
For UVA treatment, the patient is required to stand in a UVA cabinet for a period of few seconds to a few minutes.
PUVA Therapy cabinet.
Precautions.
If oral psoralen has been taken, you will need to wear UVA protection sunglasses as like skin, psoralen also sensitizes your eyes. It is therefore necessary to wear these glasses to prevent formation of cataracts. These glasses should be worn for about 12 to 24 hours after oral psoralen has been taken.
Side Effects of PUVA.
This combination proves to have the highest risks of side effects. Short term side effects of PUVA include itching and burning of the skin, nausea and headache. Long term side effects include dry skin, wrinkles and risk of skin cancer including melanoma.
Due to its skin cancer risk, long term use of this therapy is not advised. Patients who experience nausea and itching after taking oral psoralen can be switched over to topical or Psoralen baths.
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