The phototumorigenic fluoroquinolone lomefloxacin photosensitizes pyrimidine dimer formation in human keratinocytes in vitro

The fluoroquinolone antibiotic lomefloxacin is phototoxic, photogenotoxic, photomutagenic and photosensitizes tumorigenesis in mouse skin. We have use d T4 endonuclease V to demonstrate that lomefloxacin photosensitizes pyrimi dine dimer formation in a human keratinocyte line (HaCaT). A possible mecha nism for this effect would be triplet-triplet energy transfer. However, the re is indirect evidence that the lomefloxacin triplet yield is very low, ma king this reaction less likely, The finding that lomefloxacin photosensitiz es production of highly mutagenic pyrimidine dimers correlates with its abi lity to initiate skin tumor formation in mice. Until the potential of other fluoroquinolones to photosensitize dimer formation is explored it may be u nadvisable to prescribe these antibiotics to patients with defective DNA re pair capacity (e.g. xeroderma pigmentosum).