H2RA

• Histamine 2 receptor antagonists

  inhibit acid secretion to treat GERD, ulcers, heartburn, and indigestion
• H2RA pharmacodynamics


  Reversible competitive blockers of histamine at histamine 2 receptors

  highly selective

  inhibits all phases of gastric acid secretion

  They do not inhibit acetylcholine unlike antihistamines
• H2RA examples


  Cimetidine, Famotidine, Nizatidine, Ranitidine
• H2RA precautions and contraindications

  Caution in renal impairment

  Ranitidine has least renal toxic effects, Cimetidine the most

  contraindicated in liver disease

  caution in liver impairment
• Adverse reactions H2RAs


  Cimetidine has greatest risk of adverse reaction

  CNS effects, mental confusion, agitation, depression

  agranulocytosis, thrombocytopenia

  drowsiness, dizziness, constipation
• H2RA monitoring


  monitoring should occur in those with liver or renal impairment
• H2RA education


  take dose if missed but do not double the dose

  taken with meals or immediately after and at bedtime

  once daily are best taken at bedtime

  avoid taking with antacids or cytoprotective agents, wait at least 2 hours

  may cause drowsiness or dizziness

  cimetidine has the potential for gynecomastia and impotence

  don't smoke and eat right