phototherapy and photochemotherapy

Types of treatment

UVB radiation (high energy) is quickly absorbed in the epidermis, while UVA (lower energy) penetrates further into the skin, reaching the deeper layers of the dermis
The difference in level of penetration determines which form of phototherapy is best suited as a treatment for individual conditions
- Examples of common conditions treated - psoriasis, atopic aczema, vitiligo, urticaria, granuloma annulare
- UVB generally first line (after topical therapies)
- PUVA used where UVB has proved ineffective or where disease relapses quickly
- PUVA first choice for mycosis fungoides, pityriasis rubra pilaris, pustular psoriasis or erthrodermic psoriasis
- UVA1 is a relatively new treatment, used less commonly

Normally given 3x weekly
Erythema is a common side effect
- Peaks 12-24 hours after treatment so at least one treatment free day is allowed between exposures to assess the erythema response
Before starting treatment patient should have a Minimal Erythema Dose (MED) test
- Ensures a safe starting dose for treatment and excludes any abnormal reaction to light
- Treatment started at 70% of this dose

Usually given 2x weekly
Delated erythemal reaction peaking at 96 hours after exposure - needs at least 2 full treatment free days between treatment to assess response
Psoralen can be given orally, added to bath water in which patient soaks for 15 mins prior to treatent, or (less commonly) applied to skin as a gel before treatment
- Oral psoralen - 8 methoxypsoralen first line, can cause nausea, if nausea not eased by having a light snack before taking the tablet try 5 methoxypsoralen
Patients beginning oral or bath PUVA should have a Minimal Phototoxic Dose (MPD) test
- Ensures a safe starting dose for treatment, excludes any abnormal reaction to light and ensures an adequate dose of psoralen is present in the system to allow the PUVA to be effective

Same as NB-UVB, also psoralen induced: