Lin M S, Sun P, Yu H Y
School of Pharmacy, College of Medicine, National Taiwan University, Taipei, Taiwan.
J Formos Med Assoc. 1998 Oct;97(10):704-10.
The antacid properties of seven antacids listed in the hospital formulary of a medical center were evaluated with in vitro tests. These included not only 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 HCl 10 minutes after addition of the minimum recommended dose of an antacid, while the neutralizing capacity test measured the amount (mEq) of HCl 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 acid-neutralizing 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 hours. 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 level. 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.
通过体外试验对某医疗中心医院处方中列出的7种抗酸剂的抗酸性能进行了评估。这些试验不仅包括美国药典（USP XXIII）中所述的初步抗酸试验和酸中和能力试验，还包括缓冲pH曲线试验。初步抗酸试验测量在加入抗酸剂最小推荐剂量10分钟后10 mL 0.5 N盐酸溶液的最终pH值，而中和能力试验测量在15分钟内抗酸剂最小推荐剂量中和的HCl量（mEq）。缓冲pH曲线记录了一剂抗酸剂动态模拟胃液中和的pH时间过程。在初步抗酸试验中，氧化镁的pH值最高（9.52±0.14，平均值±标准差，n = 3）；磷酸铝凝胶的最终pH值为2.51±0.01，因此不符合抗酸剂标准（pH＞3.5）。在酸中和能力试验中，水滑石的中和能力最高（28.26±0.3 mEq），而碳酸氢钠最低（7.40±0.12 mEq）。在缓冲pH曲线试验中，氢氧化铝镁混悬液和水滑石片在约1.5小时内维持稳定的最佳pH值（3 - 5）。一片碳酸钙、碳酸氢钠或氧化镁不能将胃pH值提高到3以上，但两片会使pH值过度升高（5.3至8.6）。较高剂量（两片）的己糖醇氢氧化铝复合物不能将pH值提高到最佳水平。这些发现表明，通过中和能力试验和缓冲pH曲线试验估计的抗酸效果存在差异，并表明不能根据抗酸剂的酸中和能力准确预测其疗效。抗酸剂的剂量对中和pH曲线有很大影响。铝镁化合物似乎比碳酸盐化合物或氧化镁提供更稳定的缓冲作用。
