IN-VITRO ADSORPTION-DESORPTION OF FAMOTIDINE ON MICROCRYSTALLINE CELLULOSE

The adsorption of famotidine onto microcrystalline cellulose PH-101 (MCC) was studied in buffered systems and in water/alcohol mixtures. Aqueous and alcohol systems were fitted using the Freundlich and Langmuir equations, respectively. In buffered systems where ion-pairing appeared to be the predominant mechanism of interaction, adsorption can be minimized by either increasing the ionic strength or decreasing the pH. In the hydroalcoholic mixtures, the non-electrostatic interactions (such as hydrogen bonding) are dominant and famotidine adsorption is markedly decreased. Adsorption also decreases with increasing alcohol content. The free energies of adsorption were calculated in the case of alcohol/water mixtures in the range of temperature investigated (15-45 degrees C). They showed that the adsorption process is exothermic. Finally, it was shown that the adsorbed famotidine molecules were completely desorbed at pH 2.