Photoallergenicity of a fluoroquinolone antibacterial agent with a fluorine substituent at the 8-position in guinea pigs exposed to long-wavelength UV light.

The 8-position of the quinolone ring of balofloxacin (BLFX), one of fluoroquinolones, was replaced with fluorine to obtain the 8-F. When an aqueous solution of bovine serum albumin (BSA) containing the 8-F was exposed to long-wavelength UV light (UVA) at a rate of 2.5 J/cm2, the absorbance of BSA at 300 nm or longer wavelengths increased markedly in comparison to that of native BSA. In addition, when a homogenate of skin tissue from Hartley guinea pigs was exposed to UVA (2.5 J/cm2) in the presence of the 8-F and then injected subcutaneously into guinea pigs, the animals produced IgG class antibody specific to the 8-F and its UVA-irradiation product. No such phenomenon, however, was observed when the parent compound, i.e. , BLFX which possesses a methoxy group at the 8-position, was used instead of the 8-F. In a subsequent experiment, the 8-F was administered either orally or topically to the shaved neck of guinea pigs and then irradiated with UVA (5 J/cm2) once daily for 5 days. When the treated animals were challenged by a combination of UVA irradiation (5 J/cm2) and either an oral or intradermal administration of the 8-F, 2 and 3 of the 5 animals showed redness and erythema on the irradiated area, respectively. However, no change was observed when BLFX was used instead of the 8-F. These results suggest that the introduction of a fluorine substituent to the 8-position of quinoline ring of fluoroquinolones induces photoallergic responses in which the fluoroquinolone or its photo-denatured product(s) act as an allergen.

Reduced phototoxicity of a fluoroquinolone antibacterial agent with a methoxy group at the 8 position in mice irradiated with long-wavelength UV light.

A newly developed fluoroquinoline, Q-35 (8-OCH3), in which a methoxy group was substituted at the 8 position of the quinoline nucleus, was very stable under irradiation with long-wave UV light (UVA). Derivatives, a fluoroquinolone with no substitution (the 8-H analog) and one in which a fluorine was substituted (the 8-F analog), were degraded in their solutions by the UVA irradiation. The phototoxic inducibility by these derivatives was further studied in a murine model. When mice were dosed orally with 800 mg of Q-35 (8-OCH3) per kg of body weight, the maximum dose given, and exposed to the UVA light, no inflammatory lesions were observed in their ears. Ear redness was marked in mice given more than 12.5 mg of the 8-F analog or 200 mg of the 8-H analog per kg. Histopathological changes, edema, and infiltration of neutrophils were also observed microscopically in groups receiving the 8-H or 8-F analog but not in groups receiving Q-35 (8-OCH3). Similar inflammatory reactions were observed to occur in a dose-dependent manner with other available fluoroquinolone antibacterial agents such as lomefloxacin, enoxacin, norfloxacin, ciprofloxacin and ofloxacin. These results suggest that the introduction of a methoxy group at the 8 position of the quinolone nucleus is important for the reduction of phototoxicity.