Using new radioimmunoassay methods, the plasma levels of clobetasol propionate and clobetasone butyrate have been measured following application of ointment to in-patients with psoriasis or eczema.

A single application of 25 g of clobetasol propionate 0·05% ointment caused a rapid rise in plasma clobetasol propionate level during the first 3 h. The level fell gradually but was still appreciable 48 h afterwards. Conversely, the plasma cortisol level fell rapidly after application and remained depressed, not rising to baseline levels until 96 h afterwards.

A single application of 30 g of clobetasone butyrate 0.·05% ointment resulted in a measurable rise in clobetasone butyrate levels during the first 3 h but then the levels fell gradually. The concentrations were approximately ten times lower than those of clobetasol propionate. The normal diurnal variation in plasma cortisol levels was not affected.