Comparative in vitro study of oesophageal adhesiveness of different commercial formulations containing alendronate.

Cases of oesophageal irritation have been reported in patients ingesting alendronate with little liquid or reclining shortly after taking the medication. Pill-induced oesophagitis principally occurs because of adherence of ingested tablets to the epithelial surface. The objective of this in vitro study was to evaluate the oesophageal bioadhesive characteristics of alendronate generics marketed in Europe, the proprietary Fosamax((R)), one negative and two positive polymer controls. A texture analyser was used for qualitative analysis and to determine the maximal detachment force and the adhesion work developed by each formulation on porcine oesophageal mucosa. Fosamax showed few or no bioadhesive characteristics, but the detachment of few tablets powder particles in some of the experiments does not preclude the potential risk of oesophageal lesions. The 10-mg generic Teva tablets had bioadhesive characteristics similar to a positive control. Other generic formulations (Alenat, Stada, Aliud, Ratiopharm showed "cleavage" rupture, leaving a large piece of the tablet mass attached to the mucosa. The bioadhesive characteristics seem to be related to the inactive ingredients: the presence of adhesive polymers such as HPC or very active disintegration agents, such as sodium croscarmellose. The demonstrated differences in adhesiveness suggest that differences in oesophageal tolerance between Fosamax tablets and generics of sodium alendronate may exist.