Effect of UV-B radiation on some common antibiotics

Abstract

Some of the commonly used antibiotics such as cephaloridine, cephalexin, cephradine, nystatin and nafcillin were tested for generation of singlet oxygen (1O2) under UV-B (290-320 nm) exposure and the order for 1O2 generation was obtained: cephaloridine > cephalexin > nystatin > cephradine > nafcillin. In vitro study with deoxyguanosine (dGuo) showed that 1O2 was responsible for drug-sensitized photodegradation of the guanine base of DNA and RNA. Sodium azide (NaN3) and 1,4-diazabicyclo [2.2.2] octane (DABCO) accorded significant inhibition (76-98%) in the production of 1O2 and photo-oxidation of dGuo. The combined effect of drug and UV-B irradiation is of paramount importance in view of cell-damaging reactions by 1O2. Our findings are important because of increasing UV-B radiation on the earth's surface due to depletion of the stratospheric ozone layer. The selected drugs are used routinely for the treatment of various diseases and their combined action may cause undesirable phototoxic responses. Our study suggests that exposure to sunlight should be avoided after the intake of the photosensitive drugs. © 2002 Published by Elsevier Science Ltd.