Histamine H2 receptors are found on the parietal cells in the stomach, a
H2-Antagonist are the class of drugs known as H2 blockers prevents histamine from acting on those receptors. Due to this, less stomach acid is produced.
This type of drug used in the treatment of gastric acid, duodenal ulcers dyspepsia, peptic ulcers, and gastroesophageal reflux disease.
Medical Uses of H2 antagonist-
Gastroesophageal reflux disease
Dyspepsia
Stress ulcers
Prevention of aspiration pneumonitis during surgery.
Side effects-Blurred vision
Hypotension
Headache
Tiredness
Dizziness
Diarrhoea
Constipation
Rash
Mechanism of action
When histamine releases, it binds with H2 receptor.
H2 receptor ae also G-protein coupled receptors, so it activates cAMP.
This cAMP increases the Ca++ which further increases the or activates the proton pump and increase the secretion of H+, which further increases the production of HCl.
H2- Antagonist blocks the receptors so all the mechanism inhibits, and all the action of histamine reduced. So HCl secretion decreases.
Here is the diagram for the classification of H2-antagonists: