The H2 Antagonists are a class of drugs which block the action of histamine at the histamine H2 receptors of the parietal cells in the stomach, decreasing the production of stomach acid. They can be used to treat dyspepsia, peptic ulcers and gastroesophageal reflux disease but have been largely surpassed by the more effective proton pump inhibitors (eg omeprazole) for this.
H2 Antagonists:
eg: Cimetidine (Tagamet); Ranitidine (Zantac); Nizatidine (Axid); Famotidine (Pepsid)
Cimetidine, was first marketed in 1976 with the brand name Tagamet and became the first ‘blockbuster’ drug.
In 2019 the probable carcinogen N-nitrosodimethylamine (NDMA) was found in Ranitidine (Zantac) products and it has now been withdrawn by almost all regulatory authorities globally.
There is some evidence that cimetidine may be effective against verrucae.
Mechanism of Action:
The H2 antagonists selectively block H2 receptors to prevent the action of histamine at receptors on the parietal cells. This suppresses the normal secretion of acid by parietal cells.
They do not affect histamine release and do not block H1 receptors.
Side Affects:
Typical uncommon side affects of H2 antagonists include hypotension, headache, fatigue, dizziness, confusion, diarrhea, constipation and a rash.
Related Topics:
H1 Antagonists
Cimetidine (Tagamet) for Verrucae
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