by Char Brar

Created on: April 02, 2009

Antacids or gastric acid reducers are the most widely used, readily available, and comparatively inexpensive over-the-counter drugs. By the time a patient shows up at the doctor's office with complaints of stomach problems or heartburn, they have had already tried at least one of the OTC antacids. But they are not as benign as one may have thought.

There are three different classes of drugs that reduce stomach acid:

1) Antacids

2) H-2 receptor blockers

3) Proton pump inhibitors (PPIs) .

Antacids chemically neutralize or absorb the excess acid in the stomach and the duodenum. They have a rapid onset but short duration of action. 2 to 4 tablets a day may help in rapid relief of stomach discomfort for a brief period of time. There are two different types of antacids (read the labels carefully):

a). Sodium bicarbonate and the Aluminium antacids are known to chemically neutralize the acid directly in the stomach.

b). Non-absorbable antacids, such as calcium and magnesium salts reduce the acid in the stomach by absorbing it (like chalk would absorb ink).

The antacids are not benign. They can decrease the absorption of certain drugs such as warfarin, digoxin, ACE-Is, some anticonvulsants, and some antibiotics.

Aluminum-containing antacids may lead to constipation, and overtime may lead to phosphate depletion in the bones.

The magnesium-containing antacids can produce diarrhea, and lead to an increased magnesium levels in the blood. They should be avoided or used with caution in patients with kidney problems.

Calcium-containing antacids, such as TUMs are often used as calcium supplements, especially in postmenopausal women. However they may cause acid rebound due to a paradoxical increase in gastrin secretion and acid production. Calcium antacids can also lead to constipation, and their excess consumption can lead to too much calcium in the body, alkalosis, and renal insufficiency (the milk-alkali syndrome).

Histamine (H2 receptor)Blockers : These work by blocking histamine release. Histamine stimulates acid secretion in the stomach. H2 blockers like Cimetidine, Ranitidine and Famotidine stop acid production and thus prevent ulcers formation. The oral H2 blockers are absorbed rapidly and reach their peak levels within 1 to 2 hours. H2 blockers are effective in treating duodenal ulcer and, gastric ulcer, but they are not as effective as the proton pump inhibitors. All H2 blockers are mainly metabolized through liver and kidneys, except nizatidine, which is metabolized through kidney.

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