Quantification of UV-Induced Skin Erythema before Phototherapy in Individuals taking Hydrochlorothiazide and Controls

The association with the intake of thiazide medication and an increased photosensitivity was investigated by testing 15 patients on thiazide medication and 15 controls with stepwise UVA-, UVB- and UVB 311 nm-irradiation. Erythema and blood flow 24 h after irradiation were quantified by visual assessment (MED) and objective methods (Dermacatch, Minolta Chromameter, laser doppler flowmetry). A higher UVA-photosensitivity in patients taking thiazides was found by visual assessment. The sensitivity and specifity of the different devices was compared; objective measurement of erythema in all chosen wavelengths generally showed the best results with laser doppler flowmetry closely followed by colorimetry. Phototherapy in patients on thiazide medication should be carried out with caution since many factors of pharmacologically increased photosensitivity are still not explored, but it can be assumed that for the frequently used UVB 311 nm phototherapy no special precautions need to be taken.