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摘要

本篇出處 臺灣醫學會雜誌 97:10 民87.10 頁704-710
篇名 Evaluation of Buffering Capacity and Acid Neutralizing-pH Time Profile of Antacids
作者 林美淑 ; 孫斌 ; 余秀英
英文摘要        The antacid properties of seven antacids listed in the hospital formulary of a medical center were evaluated with in vitro tests. These included not noly the preliminary antacid test and acid-neutralizing capacity test as described in the United States Pharmacopeia (USP XXⅢ), but also a buffering pH profile test. The preliminary antacid test measured the final pH of a 10-mL solution of 0.5 N HCI 10 minutes after addition of the minimum recommended dose of an antacid, while the neutralizing capacity test measured the amount (mEq) of HCI neutralized by the minimum recommended dose in 15 minutes. The buffering pH profile recorded the pH time course of dynamic simulated gastric fluid neutralization by a dose of an antacid. In the preliminary antacid test, magnesium oxide showed the highest pH (9.52±0.14,mean±standard deviation, n=3) ;aluminum phosphate gel yielded a final pH of 2.51±0.01, thus failing to meet the criteria of an antacid (pH>3.5). In the acidneutralizing capacity test, hydrotalcite had the highest neutralizing capacity (28.26±0.3 mEq), while sodium bicarbonate had the lowest (7.40±0.12 mEq). In the buffering pH profile test, aluminum-magnesium hydroxide suspensions and hydrotalcite tablets maintained a steady optimum pH (3-5) for around 1.5 horus. One tablet of calcium carbonate, sodium bicarbonate or magnesium oxide could not raise the gastric pH to above 3, but two tablets increased the pH excessively (5.3 to 8.6). The higher dose (two tablets) of aluminum hydroxide hexitol complex could not raise the pH to the optimal leval. These findings demonstrate that there is disparity in the antacid effectiveness estimated by the neutralizing capacity test and the buffering pH profile test and suggest that the efficacy of an antacid cannot be accurately predicted from its acid-neutralizing capacity. The dose of antacids greatly influences the neutralizing pH profiles. Aluminum-magnesium compounds appear to provide steadier buffering than carbonate compounds or magnesium oxide.