Photoinduced free radicals from chlorpromazine and related phenothiazines: Relationship to phenothiazine-induced photosensitization

Chlorpromazine and several other related phenothiazines are known to cause both phototoxic and photoallergic reactions in the skin and eyes of patients receiving these drugs. While the detailed mechanisms of photosensitization are not known, it is obvious that the first step must be the absorption o...

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Bibliographic Details
Main Authors: Chignell, C F, Motten, A G, Buettner, G R
Format: Book Chapter
Language:English
Online Access:Get full text
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Summary:Chlorpromazine and several other related phenothiazines are known to cause both phototoxic and photoallergic reactions in the skin and eyes of patients receiving these drugs. While the detailed mechanisms of photosensitization are not known, it is obvious that the first step must be the absorption of light by the drug, its metabolites, or photoproducts, or possibly an induced endogenous chemical. In this review, the free-radical photochemistry of phenothiazines is described, and the evidence for the involvement of photoinduced free radicals in photosensitization is examined. Upon irradiation chlorpromazine yields a variety of free radicals including the corresponding cation radical (via photoionization), the neutral promazinyl radical and a chlorine atom (Cl super(.)) (via homolytic cleavage), and a sulfur-centered peroxy radical. The chlorpromazine cation radical is probably responsible for some of the observed in vitro phototoxic effects of this drug.
ISSN:0091-6765