HISTAMINE TYPE 2 ("H-2") BLOCKERS

 
Drug Duodenal Ulcer Gastric Ulcer* Maintenance Dose GERD
Cimetidine 800mg HS x 4-6wks 400mg BID x 6-8wks 400mg HS 400-800mg BID or 400QID
Ranitidine 300mg HS x 4-6wks 150mg BID x 6-8wks 150mg HS 150mg BID - 300mg QID
Nizatidine 30mg HS x 4-6wks 150mg BID x 6-8wks 150mg HS 150-300 BID
Famotidine 40mg HS x 4wks 20mg BID x 6-8wks 20mg QHS 20-40mg BID

I. Pharmacology

  1. Inhibit the type 2 histamine receptor, which stimulates gastric acid secretion
II. Adverse effects
  1. H2-blockers in general
    1. In a prospective study of a population of 364,000 pts over 3y, use of either H2-blockers or PPIs were ass'd with RR 4.5 for incidence of community-acquired pneumonia (JAMA 292:1955, 2004--JW)
  2. Cimetidine
  1. Cimetidine is cheapest but can cause gynecomastia (0.2%), impotence, confusion, dizziness, somnolence; also occur but are rarer with ranitidine. Unknown as of 1990 whether occur with famotidine or nizatidine
  2. Cimetidine inhibits cytochrome P450 pathway, interfering with benzos, coumadin, dilantin, propanolol, theo; others don't
  1. Famotidine--Can cause HA, decreased libido, depression, mild increase in transaminases
  2. Nizatidine--Can cause sweating, urticaria (< 1%), somnolence, increase in transaminases