IN-VITRO ADSORPTION-DESORPTION OF FAMOTIDINE ON MICROCRYSTALLINE CELLULOSE

The adsorption of famotidine onto microcrystalline cellulose PH-101 (M CC) was studied in buffered systems and in water/alcohol mixtures. Aqu eous and alcohol systems were fitted using the Freundlich and Langmuir equations, respectively. In buffered systems where ion-pairing appear ed to be the predominant mechanism of interaction, adsorption can be m inimized by either increasing the ionic strength or decreasing the pH. In the hydroalcoholic mixtures, the non-electrostatic interactions (s uch as hydrogen bonding) are dominant and famotidine adsorption is mar kedly decreased. Adsorption also decreases with increasing alcohol con tent. The free energies of adsorption were calculated in the case of a lcohol/water mixtures in the range of temperature investigated (15-45 degrees C). They showed that the adsorption process is exothermic. Fin ally, it was shown that the adsorbed famotidine molecules were complet ely desorbed at pH 2.