In vitro adsorption of propranolol hydrochloride by various antacids

The purpose of this study was to investigate by in vitro methods whether an interaction takes place between propranolol hydro-chloride and adsorbents when antacids are taken concomitantly with the beta-blocker or when excipients having adsorbent properties are present in formulations of the drug products containing propranolol hydrochloride. Specific surface areas of magnesium trisilicate, magnesium oxide, magnesium hydroxide, dihydroxy aluminum sodium carbonate, magnesium carbonate and kaolin were calculated from nitrogen adsorption isotherm using single pint method and it was found. that magnesium trisilicate has the largest specific surface area. The adsorption of propranolol hydrochloride to these adsorbents was investigated by in vitro methods. The adsorption isotherms were drawn and the adsorptive capacities of the adsorbents were calculated from the slopes. It was found that magnesium tri-silicate, magnesium hydroxide arid dihydroxy aluminum sodium carbonate possess the highest adsorptive capacities while kaolin and magnesium carbonate possess the lowest. The results of the adsorption studies indicate that the concomitant use of propranolol hydrochloride and the above mentioned adsorbents could affect the bioavailability of the beta-blocker adversely.