Time course of 8-methoxypsoralen-induced skin photosensitization in PUVA-bath photochemotherapy.
In recent years PUVA-bath photochemotherapy has been shown to be an effective treatment modality for several dermatoses. A limitation of PUVA-bath photochemotherapy has been the lack of guidelines for optimal performance, including the time course of photosensitization of the skin exposed to the 8-methoxypsoralen (8-MOP) bath water solution. In the present study 12 healthy volunteers were exposed to a 20 min bath in 150 l of an 8-MOP water solution (0.5 mg/l, 37 degrees C). Immediately, as well as 1, 2, 3 and 5 h after the 8-MOP bath, irradiation was performed with increasing doses of UVA (0.5, 1, 2, 3, 5 J/cm2) on 2 cm2 test areas. The minimal phototoxic dose (MPD) was determined 72 h after the UVA exposure. In all volunteers, photosensitization was highest immediately after the bath, with a MPD significantly below 5 J/cm2 (0.5-2 J/cm2). One hour after the bath, erythema could be induced by 2 to 5 J/cm2 UVA. Two hours after the bath, erythema could be induced using irradiation of 5 J/cm2 only in two volunteers. Three and five hours after the 8-MOP bath, no erythema could be induced in any volunteer by UVA doses up to 5 J/cm2. Our results indicate that optimal bath-PUVA requires UVA irradiation immediately after the 8-MOP bath. Further, these results imply that no restrictions on further sun exposure are mandatory 3 h after the 8-MOP bath, thus allowing the patient to pursue normal life activities.
Reuther
T
T
Ruhr-University, Bochum, Germany.
Gruss
C
C
Behrens
S
S
von Kobyletzki
G
G
Neumann
N
N
Lehmann
P
P
Altmeyer
P
P
Kerscher
M
M
D004890:Erythema / Q000209:etiology; D005260:Female; D006801:Humans; D008297:Male; D008730:Methoxsalen / Q000627:therapeutic use*; D011701:PUVA Therapy; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D012867:Skin / Q000528:radiation effects*; D013997:Time Factors
D017319:Photosensitizing Agents; D008730:Methoxsalen