The UVR wavelength dependence for lomefloxacin photosensitization of human skin.

Lomefloxacin is a new fluoroquinolone with effective broad-spectrum antimicrobial activity. However, in common with other structurally related drugs, skin photosensitization reactions have been reported. The wavelength dependence for such photosensitization has been investigated on the previously unexposed buttock skin of 12 normal healthy human volunteers of skin types I and II. Using geometric square root of 2 dose increments, baseline 24 h minimal erythema doses were assessed at 300, 320, 330, 340, 350 and 360 nm, and with broad-band UVA. In addition, dose-response curves were constructed for erythema as measured by a reflectance device. Subjects received single daily oral doses of 400 mg lomefloxacin at specified times for 4 days. At 2 h after the final dose, new areas of buttock skin were irradiated to assess changes in minimal erythema dose and erythema dose-response. Convolution of the erythema action spectra obtained pre- and on-drug with a terrestrial solar spectrum showed that, although the UVA sensitivity on-drug was enhanced, most of the erythemally effective solar energy was still in the UVB region. An action spectrum derived for lomefloxacin skin photosensitization showed peak activity at 320 nm, the same spectral region as that for maximal absorption of the drug. There was no evidence of skin photosensitization at 300 nm.