Phototoxic reactions are the most common drug-induced photoeruptions (Figures 199-3, 199-4, 199-5, 199-6, and 199-7). They are caused by absorption of ultraviolet rays by the causative drug, which releases energy and damages cell membranes, or, in the case of psoralens, DNA. The drugs that most frequently cause phototoxic reactions are NSAIDs, quinolones, tetracyclines, amiodarone, and the phenothiazines3 (Table 199-2). Most of these drugs have at least one resonating double bond or an aromatic ring that can absorb radiant energy. Most compounds are activated by wavelengths within the UVA (320 to 400 nm) range, although some compounds have a peak absorption within the UVB or visible range.