In vitro adsorption of some corticosteroids on antacids.

The adsorption of prednisone, prednisolone, fluprednisolone, betamethasone, triamcinolone, beta-methylprednisone acetate and hydrocortisone acetate on various antacids or adsorbents was studied at 37 degrees C. The antacids or adsorbents used were magnesium trisilicate, aluminum hydroxide, bismuth oxycarbonate, magnesium oxide, magnesium carbonate, calcium carbonate, talc, kaolin and charcoal. Magnesium trisilicate and charcoal had the highest adsorption capacity for the corticosteroids tested. Bismuth oxycarbonate and talc had intermediate adsorption properties while kaolin and aluminium hydroxide had lower effects. Other antacids were without any adsorption character. Results of the elution study confirmed the higher affinity of magnesium trisilicate over that of bismuth oxycarbonate and talc for the steroids tested. Further in vivo testings are still needed to assess the effect of antacids on the bioavailability of coadministered corticosteroids.