Pharmacokinetics and rectal bioavailability of hydrocortisone acetate

The pharmacokinetics and bioavailability of hydrocortisone after rectal administration of a hydrocortisone acetate foam was determined. Endogenous hydrocortisone was suppressed by dexamethasone administration. Plasma levels were compared with those observed after iv and oral administration. Only a very small part of the rectal dose (100 mg) was absorbed; the mean absolute bioavailability was 2%. There was substantial intersubject variability. Maximum hydrocortisone levels were reached after 2 h and averaged 35 ng/mL. These levels were 10-fold lower than those obtained after oral administration of a fivefold lower dose (20 mg) of hydrocortisone in the same subjects.