The hydrocortisone pharmacokinetic profiles of hydrocortisone acetate foam (Proctocort) administered rectally was assessed in healthy volunteers and patients with ulcerative colitis or X-irradiation colitis. Endogenous production of hydrocortisone was suppressed by dexamethasone. Comparison of these data with those obtained after intravenous administration enabled assessment of absolute bioavailability, which was 30.0 +/- 15.1% in healthy volunteers vs. 16.4 +/- 14.8% in patients (P = 0.09). Maximal concentrations of hydrocortisone were also decreased in patients, 277 +/- 215 nmol/L vs. 610 +/- 334 nmol/L (P = 0.03). There was a nonsignificant tendency to faster absorption of hydrocortisone in patients vs. healthy volunteers, as the times to peak concentration were, respectively, 2.5 +/- 1.2 h vs. 2.8 +/- 0.8 h (P = 0.64), and the mean absorption times were 1.96 +/- 1.45 h vs. 2.54 +/- 1.62 h (P = 0.46). Thus, rectal inflammation resulted in a lower absorption of hydrocortisone. In addition systemic plasma levels remained in the physiological range, so that only minor side effects are to be expected.