Photoirritation and Photococarcinogenicity

Photobiology is the study of the effect of UVA or UVB, visible, and infrared radiation on living systems.12 The first 

Handbook of Pharmaceutical Manufacturing Formulations Semisolid Products 

Data from animals and humans indicate that at least some photoirritants enhance UV-associated skin carcinogenesis. 8-Methoxypsoralen (8-MOP), used in psoralen plus UVA treatment therapy,12 is considered to be a photococarcinogen in humans, whereas several fluoroquinolones have been demonstrated to be photoirritants and photochemical carcinogens in hairless mice.11 However, data for many other classes of pharmaceuticals are unavailable. 

Changes in the optical properties of the skin, such as those caused by a drug vehicle, can result in a greater UV dose to the viable layers of the skin. Data on correlation of latitude, UV exposure, and cancer risk in humans indicate that an increase in UV exposure as small as 20% could result in a fourfold increase in basal-cell carcinoma.16 

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