Toggle Main Menu Toggle Search

Open Access padlockePrints

The effect of methoxsalen dose on ultraviolet-A-induced erythema

Lookup NU author(s): Professor Peter Farr

Downloads

Full text for this publication is not currently held within this repository. Alternative links are provided below where available.


Abstract

There is considerable interindividual variation in bioavailability of Methoxsalen (8-methoxypsoralen) after ingestion of the standard dose used in photochemotherapy (psoralen plus ultraviolet A). A dose change may be used to alter the degree of photosensitivity, although there is limited information on the effect of 8-methoxypsoralen dose alterations on phototoxicity within individuals. We studied the effect of changes of 8-methoxypsoralen dose over a narrow range in 15 subjects with psoriasis. Two hours after ingestion, serum 8-methoxypsoralen concentration was determined and phototesting was performed at 350 +/- 30 nm (0.45-14 J per cm(2)), The minimal phototoxic dose at 72 h was recorded, erythema was measured using a reflectance instrument, and dose-response curves were constructed. Each subject was tested on three occasions using doses of 25 mg per m(2) (conventional dose) or conventional dose +/- 10 mg, Median serum 8-methoxypsoralen concentration increased from 96 to 143 to 229 ng per mi with dose increases from conventional dose - 10 mg to conventional dose and conventional dose + 10 mg, respectively (p < 0.001). The median minimal phototoxic dose and D-0.025 (the objective equivalent of the minimal phototoxic dose derived from the dose-response curve) were significantly reduced with increasing 8-methoxypsoralen dose from conventional dose minus 10 mg (minimal phototoxic dose 1.7 J per cm(2); D-0.025 2 s J per cm(2)) to conventional dose (1.2; 1.4 J per cm(2)) and conventional dose plus 10 mg (0.9; 1.0 J per cm(2)) (p < 0.001). Change in 8-methoxypsoralen dose had no detectable effect on the maximum slope of the psoralen plus ultraviolet A erythema dose-response curve. Thus, 8-methoxypsoralen dose changes within individuals, over a narrow but clinically relevant range, significantly altered the threshold response to psoralen plus ultraviolet A erythema but not the rate of increase in erythema with increasing ultraviolet A dose.


Publication metadata

Author(s): Farr PM; Ibbotson SH; Dawe RS

Publication type: Article

Publication status: Published

Journal: Journal of Investigative Dermatology

Year: 2001

Volume: 116

Issue: 5

Pages: 813-815

ISSN (print): 0022-202X

ISSN (electronic): 1523-1747

Publisher: Nature Publishing Group

URL: http://dx.doi.org/10.1046/j.1523-1747.2001.01348.x

DOI: 10.1046/j.1523-1747.2001.01348.x


Altmetrics

Altmetrics provided by Altmetric


Share