RESUMO
Doxycycline is considered as the most phototoxic drug in tetracycline group. Its phototoxic potential has been demonstrated in human being as well as in laboratory animals. The aim of the resent work was to evaluate the possible protective effect of Ginkgo biloba extract, against doxycycline-induced phototoxicity. The study was performed on Swiss albino mice. Doxycycline [400 mg/kg] was administered orally. Two dose levels of Ginkgo biloba extract were utilized [100 and 200 mg/kg p.o.]. Mice were exposed to UV-A radiation one hour after administration of doxycycline. UV-A radiation was directed to the animal's ears for 210 min. at a dose of 25 Jol/cm[2]. Immediately after irradiation, animals were given a single dose of Ginkgo biloba extract. Twenty four hours later, the erythmatous photoreaction was examined by the naked eye according to a score index. Edema was evaluated by measuring ear pinna thickness using digital micrometer. Ears were then excised and subjected to histopathological evaluation. The obtained results showed significant protection by Kingo biloba extract against doxycycline-induced phototoxicity. The protection was dose dependent, where each of erytherma and ear pinna thickness were reduced by 33% and 44%, and 28% and 39% following the low and high used doses of Ginkgo biloba extract, respectively