Histamine receptor 2 inhibitors (PUD)

Histamine receptor 2 inhibitors

Mechanism Of Action:
Histamine has 2 types of receptors. One is Histamine 1 and other is histamine 2. Activation of histamine 1 receptors produce classic symptoms of inflammation and activation of histamine 2 increase the secretion of HCL by parietal cells in the stomach.
Histamine receptors 2 blockers decrease the acid production by parietal cell in the stomach.


  • Cimetidine ( First drug in this class and used less frequently because of numerous drug-drug interactions, inhibits hepatic drug-metabolizing enzymes and it must be taken 4 times a day.)
  • Famotidine
  • Nizatidine
  • Ranitidine

Side effects:

  • Headache
  • Dizziness
  • Diarrhea
  • Constipation
  • Nausea
  • Vomiting
  • Sedation
  • Confusion
  • Excitation


  • Since, it decrease the acid production in the stomach, it is mainly used for the PUD (Peptic ulcer disease)
  • H2 blockers are sometimes used to prevent ulcers in people who take NSAIDs long-term (for example, for arthritis).
  • GERD (gastroesophgeal reflux disorder)

Nursing consideration:

  • Continue to monitor periodic hepatic and renal function tests and CBC, platelets, and electrolyte levels.
  • Take at bedtime is it is once a day
  • Long-term use can cause gynecomastia, and impotence, in men and breast tenderness in women.
  • Avoid taking 1 hr before and after taking antacids. Antacids can reduce the absorption of drugs.
  • Dizziness and drowsiness from these drugs may occur. Therefore special precautions should be taken to reduce falls.