From the Guidelines
H2 (Histamine-2) blockers are a class of medications that reduce acid production in the stomach.
Key Characteristics
- They work by blocking the action of histamine, a chemical that stimulates the production of stomach acid [ 1 ]
- Common examples of H2 blockers include ranitidine, famotidine, and cimetidine [ 1 ]
- They are often used to treat conditions such as gastroesophageal reflux disease (GERD), peptic ulcers, and mastocytosis [ 1 ]
Clinical Uses
- H2 blockers can be used to prevent stress ulcers in critically ill patients [ 1 ]
- They can also be used to treat gastrointestinal symptoms associated with mastocytosis, such as diarrhea and abdominal pain [ 1 ]
Important Considerations
- H2 blockers may have side effects, such as cognitive decline and cardiotoxicity, especially in elderly patients [ 1 ]
- They may also interact with other medications, such as antacids and proton pump inhibitors [ 1 ]
From the Research
Definition and Function of H2 Blockers
- H2 blockers, also known as Histamine-2 blockers, are a class of compounds that inhibit the secretion of gastric acid 2, 3.
- They work by competitively blocking the histamine H2 receptors in the stomach, which are responsible for stimulating gastric acid secretion 2, 3.
- H2 blockers are used to treat conditions such as gastroesophageal reflux disease (GERD), peptic ulcers, and Zollinger-Ellison syndrome 3.
Types and Potency of H2 Blockers
- There are several types of H2 blockers, including cimetidine, ranitidine, famotidine, and nizatidine 2, 3.
- Famotidine is the most potent among marketed H2-receptor antagonists, with a potency 20-50 times higher than cimetidine and 6-10 times higher than ranitidine 2.
- The potency of H2 blockers can vary depending on the specific compound and the individual patient 2, 3.
Pharmacokinetics and Pharmacodynamics of H2 Blockers
- H2 blockers are rapidly absorbed after oral administration, with peak plasma concentrations reached within 1-3 hours 2.
- They are eliminated mainly through renal excretion, with a terminal half-life of 1-3 hours and a total body clearance of 24-48 L/h 2.
- There is a direct correlation between plasma concentrations of H2 blockers and the inhibition of gastric acid secretion, indicating a rapid equilibration between drug concentration in plasma and at the site of action 2.
Clinical Uses and Potential Side Effects of H2 Blockers
- H2 blockers are effective in reducing gastric acid secretion and are used to treat various gastrointestinal disorders 3, 4.
- They may also have potential uses in treating other conditions, such as neurodegenerative disorders and leukemia, although more research is needed to confirm this 5, 6.
- H2 blockers can have cardiac effects, including increased force of contraction and heart rate, which may be beneficial in certain conditions such as congestive heart failure, but may also be a concern in other situations 6.