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Photocontact allergic and phototoxic studies of chlorproethazine
Alastair Kerr and James Ferguson
Photobiology Unit, Ninewells Hospital, Dundee DD1 9SY, Scotland, UK
Neuriplege® cream was available as a non-prescription medication in France as a muscle relaxant, until its removal from the market in January 2007. The active ingredient is chlorproethazine (CPE), a derivative of the phenothiazine chlorpromazine. We investigated the photocontact allergic and phototoxic potential of Neuriplege® cream and CPE by means of an in-vitro phototoxic study and volunteer photopatch testing.
The in-vitro phototoxicity study was performed in HaCaT keratinocytes using the neutral red dye phototoxic assay, which showed clear evidence of phototoxicity. The concentration of CPE required to reduce dye uptake by 50% was 0.9 µg/ml in the presence of 5 J/cm2 UVA light and 11.9 µg/ml without UVA light exposure. Therefore, a one hour incubation of keratinocytes with CPE was approximately 13 times as toxic to the cells in the presence of UVA light compared to incubation with the drug alone.
Of 2 healthy volunteers photopatch tested to Neuriplege® cream, one developed a phototoxic reaction. These 2 volunteers were then photopatch tested to Neuriplege® and CPE with 7 additional healthy volunteers. Both of the initial study volunteers revealed a photocontact allergic reaction to the Neuriplege® as is upon re-exposure and one also reacted to 10% CPE in white soft petrolatum (WSP). Of the 7 volunteers not previously exposed to Neuriplege as is, 5 developed phototoxic reactions, with similar but less pronounced phototoxic reactions seen when 10% CPE was used.
These studies demonstrate the strong phototoxic and photocontact allergic sensitisation potential of CPE in Neuriplege® cream. Its previous availability to consumers within the European Union means many have been sensitised.
Kerr AC, Woods JA, Ferguson J. Photocontact allergic and phototoxic studies of chlorproethazine. Photoderm Photoimmunol Photomed 2008; 24: 11-15.
© Alastair Kerr and James Ferguson (text) and Radoslaw Spiewak (source code).
This page is part of the website photopatch.eu (contact).
Document created: 30 August 2009, last updated: 7 September 2009.