Bioequivalence (bioavailability) of generic topical corticosteroids.

A new, quantitative modification of the vasoconstrictor assay was used to measure bioavailability of generic topical corticosteroid products in two categories: betamethasone valerate 0.1% cream and triamcinolone 0.1% cream. Betamethasone valerate products could be separated into two distinct categories, and triamcinolone acetonide products could be grouped into three categories of activity. A survey of local pharmacies showed that generic substitution would be made for the prescribed brand of betamethasone valerate in 58% of cases and for the prescribed triamcinolone acetonide 75% of the time. Because of the prevalence of generic substitution of products that may not have equivalent bioavailability, some standardization of the bioavailability of topical products is needed.