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Gastroprotective drugs are often used for the following reasons:
- Gastric and duodenal ulceration
- Gastritis
- Reflux Oesphagitis
- Rumenal Acidosis
They following are the different classes of drugs that are used as gastroprotectives.
Antacids
These are administered orally and need frequent aministration when given to small animals. They work be chemically neutralising the acidic environment of the stomach.
Examples are: magnesium carbonate, magnesium hydroxide, magnesium trisilicate, magnesium oxide, aluminium hydroxide and sodium bicarbonate.
Histamine (H2) Receptor Antagonists
Examples are cimetidine, ranitidine and famotidine.
They can be administered orally or by injection and work by inhibiting the action of histamine on parietal cells. This results in reduced production of H+ ions and pepsin secretion.
Very few side effects are noted. But cimetidine inhibits the metabolising enzymes of the liver and so slows down the rate of any drug that is given concurrently.
Proton Pump Inhibitors
An example is omeprazole that is administered orally.
It works by binding irreversibly to H+/K+/ATPase pump and so reduces the secretion of H+ from parietal cells. It will tend to accumulate in acidic areas as it is a weak base. It won't work in neutral environments.
There are few side effects. It has a long duration of action as it binds irreversibly to the proton pump.
Binding Agents
An is example is sucralfate that is administered orally.
It works by forming a viscous paste in an acidic environment, the binds and protects the mucosal surface. It also stimulates mucus and bicarbonate secretion and the production of prostaglandins.
Prostaglandin E Analogues
An example is misoprostol that is administered orally.
It works by mimicing the endogenously produced prostaglandins that are gastroprotective. This will therefore inhibit H+ production and increase mucus and bicarbonate production. It will also maintain normal mucosal blood flow.
It should be used when Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) are being used, as NSAIDs block prostoglandin formation and so the gastric lining will be more prone to damage.