Phototoxic potential of the new quinolone antibacterial agent levofloxacin in mice.

The phototoxic potential of (-)-(S)-9-fluoro-2,3-dihydro-3-methyl-10-(4- methyl-1-piperazyl)-7-oxo-7H-pyrido[1,2,3-de][1,4]benzoxazine-6- carboxylic acid hemihydrate (levofloxacin, DR-3355, CAS 100986-85-4) was evaluated by the mice ear swelling reaction. Results were compared with those for enoxacin (ENX). Mice were orally administered DR-3355 or ENX and immediately exposed to ultraviolet-A for 4 h. Phototoxicity was determined by measuring ear thickness developing 24 h after irradiation. DR-3355 provided no changes in the ear at 200 mg/kg, but caused ear swelling at 800 mg/kg. ENX caused severe phototoxicity in a dose dependent manner from 50 mg/kg. These data suggest that DR-3355 has minor phototoxic potential, but is approximately 4-fold less toxic than ENX in these experimental conditions.