Psoralen Photochemotherapy and Ultraviolet B
Title: Audit of the use of psoralen photochemotherapy
(PUVA) and narrowband UVB phototherapy in the treatment of psoriasis.
Authors: Yoness SS, et al.
Publication: J Dermatolog Treat. 2005 Apr;16(2):108-12.
Psoralen photochemotherapy or PUVA was introduced in 1974 and
had gained acceptance because of its benefits. This therapy uses
the combination of psoralen (a chemical that makes the skin more
sensitive to ultraviolet) and long wave ultraviolet (UVA) radiation.
PUVA, however, carries the increased risk of cancer after 150
to 200 exposures. To minimize this effect, a narrowband (311 to
312 nm wavelength) ultraviolet B lamp called TL-01 was introduced
in 1984. Except for severe or resistant psoriasis, this has become
the preferred photochemotherapy method.
In this study, the authors reviewed 6 months of patient’s
hospital notes (from November 2001 to April 2002) to see whether
narrowband UVB treatment followed the established British Photodermatology
Group guideline for PUVA.
The authors found that 31 patients received PUVA (18 oral, 11
bath and 2 uncertain because of missing notes) and 20 narrowband
UVB during this period and that both PUVA and narrowband UVB guidelines
were followed relatively closely. There were, however, some exceptions:
- One PUVA patients received high cumulative exposure after
mutual agreement because there was no other suitable therapy
- Failure to measure minimal phototoxic doses (MPDs) in some
- Prolonged referral delays, generally due to patient’s
Minimal Phototoxic Dose (MPD) refers
to the smallest amount of UV dose that can produce a grade E1 erythema
(faint pink), 48 hours after exposure.