Classification of Gastroprotective Agents
Pharmacological agents in this group are divided into two main categories based on their predominant mechanism of action:
- Agents that increase mucus secretion:
- Synthetic prostaglandin analogues (misoprostol, enprostil).
- Licorice derivatives (carbenoxolone).
- Agents that form a protective mechanical barrier:
- Sucralfate.
- Bismuth preparations (bismuth subnitrate, bismuth subcitrate).
Synthetic Prostaglandin Analogues
These agents mimic the action of natural prostaglandins, providing comprehensive mucosal protection.
- Misoprostol is a synthetic analogue of prostaglandin $E_1$. It stimulates the production of protective mucus and bicarbonates, the synthesis of surfactant-like phospholipids, and improves local microcirculation. The primary indication is the prevention of ulcerogenic lesions caused by nonsteroidal anti-inflammatory drugs (NSAIDs) and glucocorticoids.
- Enprostil is a prostaglandin $E_2$ analogue. Pharmacologically, it is similar to misoprostol but features better tolerability and a lower incidence of adverse effects.
Glycyrrhizic Acid Derivatives and Barrier-Forming Agents
Carbenoxolone, derived from licorice root extract, stimulates mucus production, alters its chemical composition via sialic acids, and prevents back-diffusion of hydrogen ions. Due to its mineralocorticoid activity, it can cause fluid retention and hypokalemia.
Sucralfate interacts with damaged mucosa to form an insoluble protective complex lasting up to six hours. The drug decreases pepsin activity, adsorbs bile acids, and exerts a local antacid effect without significantly altering overall gastric pH. Bismuth preparations, such as bismuth subcitrate and bismuth subnitrate, coagulate proteins to form a film and exhibit astringent properties, with bismuth subcitrate additionally inhibiting the growth of Helicobacter pylori.