Assessment and comparison of the buffering power of Cimetidine Merck, Tagamet and Azantac effervescent tablets

Anti-secretory treatment with H2 receptor antagonists (cimetidine and ranit idine) is the first-line therapy for the functional manifestations of gastr oesophageal reflux (GER). Anti-secretory anti-H2 drugs act after several te ns of minutes. In order to obtain more rapid relief for patients, effervesc ent forms of anti-H2 substances (granules and tablets) are formulated with excipients that can increase gastric pH rap idly, before a systemic anti-se cretory action. Neutralization curves were used to model variations of gast ric pH versus time and to determine its value 10 min after administering th e tablet, just before the pharmacological action of the anti-H2 compounds. Two parameters were then used to assess the buffering effect of the excipie nts in the different products: buffering powers and the acid neutralizing c apacity (ANC) defined by the USP 24(th) edition. The results showed that th e buffering effect is correlated with the quantity of buffers present in th e tablets. Among the three products indicated for gastroesophageal reflux, Cimetidine Merck 200 mg, Azantac 75 mg and Tagamet effervescent 200 mg, Tag amet was found to lead to the most rapid and long-lasting increase of gastr ic pH.