Modulation of gastric pH by a buffered soluble effervescent formulation: A possible means of improving gastric tolerability of alendronate

Gastrointestinal side-effects of alendronate (ALN) are believed to be associated with oesophageal lodging of tablets and perhaps reflux of gastric contents with alendronate under strongly acidic pH conditions. This leads to unfavourable posture restrictions when dosing. This clinical study evaluated gastric emptying and gastric pH after administration of Fosamax® tablets and a novel effervescent ALN formulation with a high buffering capacity. This novel formulation, EX101, was developed to potentially improve gastric tolerance. Gastric pH was monitored by nasogastric probes. Gastric emptying was determined simultaneously by scintigraphic imaging of 99mTc-DTPA labelled formulations. Both formulations tested rapidly cleared the oesophagus and there were no statistically significant or physiologically relevant differences in gastric emptying times. Mean pH at time to 50% gastric emptying of the radiolabel was significantly higher in EX101-treated subjects compared to those treated with Fosamax®. At time to 90% gastric emptying of the radiolabel, mean pH values were comparable. Mucosal exposure to ALN at pH less than 3 is irritating to gastro-oesophageal tissue. Ingestion of Fosamax® resulted in ALN being present in the stomach at a pH below 3 within minutes. EX101 minimised the possibility of exposing the oesophagus (in case of reflux) to acidified ALN.