In vitro/in vivo phototoxic risk assessments of griseofulvin based on photobiochemical and pharmacokinetic behaviors

The present investigation aims to establish efficacious screening strategy to clarify the phototoxic potential of pharmaceutical substances and its possible pathways by characterizing both photobiochemical properties and pharmacokinetic profiles. Photochemical behavior of griseofulvin, as model compounds, was evaluated by reactive oxygen species (ROS) assay, and the photogenotoxic potential was also assessed by DNA binding assay, DNA photocleavage assay, and atomic force microscopy. Pharmacokinetic (PK) study was also carried out after dermal and oral administration of griseofulvin in rats. ROS assay suggested the phototoxic potential of griseofulvin via type II photochemical pathways, and the photogenotoxic risk of griseofulvin was also proposed as evidenced by high affinity toward DNA and potent DNA photocleaving activity. PK profiling and in vivo phototoxicity testing demonstrated that a highly concentrated griseofulvin in the skin might cause phototoxic skin reactions in rats, whereas oral administration of griseofulvin in single dosing regimen (20 mg/kg) resulted in 103-fold less skin deposition than phototoxic skin concentration of griseofulvin. Upon these findings, the phototoxic potential of griseofulvin might not be severe at least in a single oral dosing regimen, whereas it might be phototoxic in dermal administration. The combination use of photobiochemical and pharmacokinetic data would be valuable to provide reliable prediction on phototoxic risk and possible toxic pathways of new drug entities in the early stage of drug discovery.