Pharmacokinetics and pharmacodynamics of glucocorticoid suspensions after intra-articular administration.

Triamcinolone acetonide, triamcinolone hexacetonide, and a combination of betamethasone phosphate and acetate were given intra-articularly in different doses. Plasma levels of the steroids were measured and pharmacokinetic parameters were calculated. As a pharmacodynamic parameter for systemic steroid activity, plasma hydrocortisone levels were monitored for 3 weeks. Results indicate complete absorption from the site of injection over a period of 2 to 3 weeks. Because of its lower solubility, triamcinolone hexacetonide is absorbed slower than triamcinolone acetonide, thus maintaining synovial levels for a longer time and creating lower systemic corticoid levels. Endogenous hydrocortisone suppression correlated with exogenous steroid levels. Threshold concentrations for maximum suppression were determined.