GASTROINTESTINAL AGENTS

The gastrointestinal agents are reduced to three major categories. First, anti-ulcer agents act by reducing the stomach acid content either by directly neutralizing H⁺ or reducing the amount of acid produced. Some anti-ulcer agents may act to coat existing ulcers to prevent further damage. Second, anti-emetics act on centers in the brain to reduce the incidence of vomiting. The final category serves to either speed up or slow down the intestinal system. This is accomplished by either increasing or decreasing the water content of the stool or by increasing/decreasing gastrointestinal motility.

Anti-ulcer

The Anti Ulcer Drugs are used as part of the treatment for ulcers. Ulcers are sores or raw areas that form in the lining of the stomach or the duodenum (the upper part of the intestine). Those that form in the stomach are called Gastric Ulcers; in the duodenum, they are called Duodenal Ulcers. Both types are referred to as Peptic Ulcers. For a long time, physicians thought that stress and certain foods caused ulcers.

Now they know that most ulcers are caused either by infection with a bacterium called Helicobacter Pylori or by long-term use of aspirin or other Non-Steroidal Anti-Inflammatory Drugs (NSAIDs), such as Ibuprofen. 

Antacids

Antacids are taken to relieve heartburn or indigestion caused by excess stomach acid. There are several kinds of antacids. Learn what ingredients are in each type so that you can avoid any adverse effects.

Mechanism: Neutralizes excess stomach acids

Indications: GE reflux, ulcers

Examples: Aluminum hydroxide, Magaldrate

Side effects: Constipation and hypophosphatemia (aluminum hydroxide); diarrhea and

 hypermagnesemia (magnesium hydroxide)

Histamine₂ antagonists

H₂ antagonists, also called H₂ blockers, are a class of medications that block the action of histamine at the histamine H₂ receptors of the parietal cells in the stomach. H₂ antagonists can be used in the treatment of dyspepsia, but have been surpassed by the more effective proton pump inhibitors.

Mechanism: Decreases the effect histamine has on the H₂ receptor sites. When these sites are stimulated, the parietal cells excrete gastric acid.

Indications:

Prophylactic treatment for stress ulcers and active gastric/duodenal ulcers

Examples: Cimetidine, Famotidine, Nizatidine, Ranitidine

Side effects: Headaches, dizziness, confusion

Local acting drugs

Mechanism: Acts to coat the mucosal lining as well as any preexisting ulcers

Indications: Short term treatment and prophylactic treatment of ulcers

Examples: Sucralfate

Side effects: Constipation

Cholinergic blocking agents

Mechanism:

By blocking the cholinergic receptor sites these drugs decrease intestinal motility and gastric secretions.

Indications: Peptic ulcer disease

Examples: Glycopyrrolate, Propantheline

Side effects: Tachycardia, dry mouth, constipation, urine retention.

Anti-emetics

Mechanism:

Anti-emetics tend to act on one of two sites within the brain. First, they may act directly on the vomiting center by depressing its function.

 Secondly, they may act to reduce the labyrinth function to transmit impulses to the brain.

Indications: Prevention and/or treatment of nausea and vomiting

Examples: Phenergan, Metoclopramide, Phenothiazine

Side effects: Hypotension, Dizziness, Dry mouth