In vitro evaluation of betamethasone esters for phototoxic potential.

The phototoxicity of Betamethasone valerate and betamethasone dipropionate has been investigated on irradiation in the wavelength range of 300-400 nm, using some basic in vitro phototoxicity tests. Both esters cause photohemolysis of mouse red blood cells and photoperoxidation of linoleic acid. The photoproducts of both esters have also been found to be phototoxic. The toxicity of these photoproducts increases with further irradiation; however, they exhibit toxicity, even in the dark. The efficient inhibition of photohemolysis by the well-known free radical scavengers, such as butylhydroxyanisole and reduced glutathione, and minor inhibition by singlet-oxygen quenchers, such as sodium azide, suggests that cellular damage is mainly mediated by free radicals whereas singlet oxygen plays a minor role.