Background: Retinoids are photoreactive molecules found in skin and retinal tissue. The use of retinoids in pharmacologic doses, applied topically, raises the potential of phototoxicities. Recent review articles and current US drug labeling indicate that tretinoin is a phototoxin. In developing a new formulation of topical all-trans-retinoic acid (tretinoin), formal testing of dermal photoreactions was therefore undertaken.
Methods: Four prospective, randomized, and controlled trials were carried out in healthy volunteers at two independent research facilities. Two trials examined phototoxicity following 24 h of drug exposure under occlusion (combined n=51), and two examined photoallergenicity following a 3-week, six dose induction phase (combined n=72) followed by challenge.
Results: No phototoxic or photoallergic reactions occurred with tretinoin 0.05% in a new gel formulation.
Conclusion: The findings in these studies are consistent with previous studies of tretinoin in various formulations, and support the conclusion that tretinoin appears to be neither phototoxic nor photoallergenic in vivo.