In vitro evaluation of liquid antacid products.

The in vitro neutralizing capacities, sodium content, and cost of 21 nonprescription antacid products were compared. A 5-ml sample of each antacid product was placed in a beaker using a pipette. The pipette was rinsed three times wtih purified water 5 ml, and the mixture was stirred with a magnetic stirring rod. After one minute, 1.0 N hydrochloride acid 30 ml was added to the mixture and stirring was continued for 15 minutes. The pH was then measured. Using a burette, sufficient 0.5 N sodium hydroxide was added to the mixture to raise the pH stable value to 3.5. Samples were tested in duplicate. Manufacturers were requested to provide sodium content for the antacid products, and costs were obtained based on wholesale prices. Neutralizing capacity of the antacids ranged from 1.3 to 8.7 meq/ml. Of the 21 products, 17 contained at least 90% of the claimed neutralizing capacity, as required by FDA. One product did not qualify as an antacid by FDA standards. Sodium content has been reduced in may preparations and may no longer be a factor in choosing an antacid. Chronic therapy with antacids can be expensive, and it costs more to deliver a given amount of neutralizing capacity with less concentrated antacids.