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Antacids (cont.)

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Are there any differences among the different types of antacids?

Some antacid products may neutralize more acid in the stomach than others. The way to express the ability of an antacid to neutralize acid is by determining the antacid's neutralizing capacity (ANC). The ANC is expressed as milliequivalents (mEq) of acid that is neutralized, and it measures the ability of the antacid to neutralize acids (to a ph of 3.5 to 4). Per FDA requirements, an antacid must have a neutralizing capacity of ≥5 mEq per dose. The most effective antacids should have a high acid neutralization capacity and rapid gastric acid neutralization qualities. Antacids such as sodium bicarbonate and calcium carbonate have the greatest neutralizing capacity but are not used for long periods of time due to adverse events. (Please see the sections on warnings/precautions and side effects.)

An antacid's onset of neutralizing action (how fast the drug dissolves in gastric acid) varies among different antacids. Sodium bicarbonate and magnesium hydroxide dissolve quickly and provide a rapid buffering effect, while aluminum hydroxide and calcium carbonate dissolve slowly. Antacid suspensions generally dissolve more easily than tablets or powders. If a tablet antacid is used, however, it is advisable to chew the tablets thoroughly for maximal effectiveness.

Another difference amongst the antacids is the duration of action (how long it continues to neutralize acid in the stomach). Sodium bicarbonate and magnesium hydroxide have the shortest duration of neutralizing action, while aluminum hydroxide and calcium carbonate have the longest. Combination aluminum magnesium antacids have an intermediate duration of action.

Medically Reviewed by a Doctor on 4/15/2014


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