Biotransformation of the topical glucocorticoids budesonide and beclomethasone 17 alpha,21-dipropionate in human liver and lung homogenate.

Tritiated budesonide and beclomethasone 17 alpha,21-dipropionate (BDP) were incubated with the 9000g supernatant of human liver homogenate. BDP was immediately hydrolysed to beclomethasone 17 alpha-propionate (BMP). BMP was then further biotransformed to polar metabolites. Budesonide was rapidly biotransformed (2-4 times more rapidly than BMP) to metabolites of low glucocorticoid potency. The compounds were also incubated with the 1000g supernatant of human lung homogenate. BDP was rapidly hydrolysed to BMP and then more slowly to beclomethasone. Budesonide was not biotransformed in the lung.