Levofloxacin hydrate (Cravit hydrate) is a broad-spectrum, third-generation fluoroquinolone antibiotic and optically active L-isomer of ofloxacin with antibacterial activity. Levofloxacin diffuses through the bacterial cell wall and acts by inhibiting DNA gyrase (bacterial topoisomerase II), an enzyme required for DNA replication, RNA transcription, and repair of bacterial DNA. Inhibition of DNA gyrase activity leads to blockage of bacterial cell growth.

Cell suspension samples (50 mL) (2-5×104 mast cells in each tube for dispersed skin cells or 1 ×105 mast cells in each tube for rat peritoneal cells) in duplicate are equilibrated at 37℃ for 10 min, and then added to polypropylene tubes containing 450 mL test compounds dissolved in Tyrode solution. Histamine release reaction is allowed to proceed for a further 30 min. at the end of which time the reaction is terminated by adding 2 mL ice-cold Tyrode solution and the mixture is centrifuged (450 g for 5 min at 4℃). For determination of total histamine content, mast cells are disrupted in boiling water for 10 min. Histamine concentrations in the resulting supernatant and disrupted cells are determined by the enzyme immunoassay described above. (Only for Reference)