Absorption and metabolism of orally administered beclomethasone dipropionate

Abstract

A 4 mg dose of beclomethasone‐17,21‐dipropionate‐16,16a‐ 3 H(BP2‐16‐3H) has been given orally in a capsule to 4 subiects, and 2 further subjects as a micrafine suspension. The plasma levels of radioactivity reached a peak at 3 to 5 hours equivalent to 9.6 to 15.2 ng BP2‐16‐3H per milliliter in the capsule‐treated subjects, and 20 ng BP‐16‐ 3 H per milliliter in the subjects given the suspension. Ten to fifteen per cent of the administered dose of radioactivity was excreted in the urine as both unidentified conjugated and free metabolites of the steroid. Fram radiochemical and chromatographie analyses of the feces it was estimated that 90% of the drug in the microfine suspension was absorbed compared with 61 % to 76% of that in the capsule formulation. In vitra BP2‐16‐3H was hydrolyzed by tissue and fecal esterases to beclomethasone‐17‐ propionate‐16,16a‐3H and beclomethasone‐16,16a‐ 3 H. This study has shown that the swallowed portion of an aerosol of beclomethasone dipropionate would be absorbed fram the gastraintestinal tract, and that the lack of suppressive activity on the hypothalamo‐pituitary‐adrenal (HPA) axis of patients on therapeutic doses of the aerosolized steroid is not due to malabsorption of the drug.