Determination of action spectrum for sparfloxacin-photosensitized single-strand breaks in plasmid pBR322 DNA.

Background: Various drugs have been reported to induce photosensitivity as a side effect. Sparfloxacin (SPFX) is well known to trigger dermatological phototoxicity upon solar radiation exposure.

Purpose: To prevent SPFX-induced phototoxicity, we determined the wavelength range responsible for SPFX phototoxicity.

Methods: The action spectrum for SPFX photosensitization was assessed by the formation of single-strand breaks in plasmid pBR322 DNA.

Results: The wavelengths of light leading to the formation of single-strand breaks were in the ultraviolet A (UVA) and visible ranges. In comparison with the absorption spectrum, we found that SPFX absorption primarily contributed to the action spectrum of single-strand break formation, but it even expanded to the visible range (between 320 and 480 nm) beyond the absorption wavelengths.

Conclusion: The findings suggest that protection of skin from short wavelengths of visible light beyond the absorption wavelengths as well as UVA light is of primary importance in prevention against induction of SPFX phototoxicity.