Comparison of in situ gelling formulations for the oral delivery of cimetidine.

Three liquid formulations with in situ gelling properties have been assessed for their potential for the oral delivery of cimetidine. The formulations were dilute solutions of: (a) enzyme-degraded xyloglucan, which form thermally reversible gels on warming to body temperature; (b) gellan gum and; (c) sodium alginate both containing complexed calcium ions that form gels when these ions are released in the acidic environment of the stomach. The in vitro release of cimetidine from gels of each of the compounds followed root-time kinetics over a period of 6 h. Plasma levels of cimetidine after oral administration to rabbits of each of the formulations were compared with those resulting from administration of a commercial cimetidine/alginate suspension with an identical drug loading. In vivo release characteristics of each of the in situ gelling formulations were similar to those of the commercial preparation.