H2 Receptor Antagonist

Aka: H2 Receptor Antagonist, H2 Antagonist, H2 Blocker

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II. Indications

  1. Peptic Ulcer Disease
  2. Gastroesophageal Reflux
  3. Gastritis
  4. Allergic Reaction (adjunct)

III. Mechanism

  1. Inhibits Histamine action at parietal cell H2 receptor
  2. Decreases basal and food stimulated acid secretion
  3. Inhibits 50-80% of daily gastric acid secretion

IV. Preparations: Adult

  1. Ranitidine (Zantac)
    1. Removed from U.S. market in 2020 due to NDMA contaminant (see adverse effects below)
    2. Bolus IV Dosing: 50 mg IV q6-8h
    3. Continuous IV Dosing: 6.25 mg/h IV
    4. Oral Dosing: 150 mg orally twice daily
  2. Cimetidine (Tagamet)
    1. Bolus Parenteral dosing: 300 mg IV or IM q6h
    2. Continuous IV Dosing: 37.5 mg/h IV
    3. Oral Dosing: 400-800 mg orally twice daily
  3. Famotidine (Pepcid)
    1. Oral dosing: 20 to 40 mg orally twice daily
  4. Nizatidine (Axid)
    1. Oral dosing: 150 mg orally twice daily

V. Preparations: Children

  1. Ranitidine (Zantac) 15 mg/ml oral syrup
    1. Removed from U.S. market in 2020 due to NDMA contaminant (see adverse effects below)
    2. Age <16 years old
      1. Dose: 5-10 mg/kg/day (max 300 mg) divided every 12 hours
    3. Adult dosing for over age 16 years old
      1. Dose: 150 mg twice daily
  2. Cimetidine (Tagamet) 300 mg/ml oral solution
    1. Newborns
      1. Dose: 5-10 mg/kg/day divided every 8-12 hours
    2. Infants
      1. Dose: 10-20 mg/kg/day divided every 6-12 hours
    3. Children <12 years old
      1. Dose: 20-40 mg/kg/day divided every 6 hours
    4. Adult dosing for over age 12 years old
      1. Dose: 800 mg orally twice daily
  3. Famotidine (Pepcid) 40 mg/5ml oral suspension
    1. Age 0-3 months
      1. Dose: 0.5 mg/kg/day orally daily
    2. Age 3 months to 16 years old
      1. Dose: 0.5 mg/kg orally twice daily
  4. Nizatidine (Axid) 15 mg/ml
    1. Age 6 months to 11 years old
      1. Dose: 5-10 mg/kg/day divided every 12 hours
    2. Adult dosing over age 12 years old
      1. Dose: 150 mg orally twice daily
  5. References
    1. Baird (2015) Am Fam Physician 92(8): 705-14 [PubMed]

VI. Precautions: Impaired Renal Function

  1. Creatinine Clearance <30 ml/min
    1. Give Cimetidine at half dose
  2. Creatinine Clearance <50 ml/min
    1. Give all H2 Blockers (except Cimetidine) at half dose

VII. Efficacy

  1. Similar efficacy among all 4 agents
  2. H2 Blockers are not as effective in Tobacco Abuse
    1. Carafate and Prilosec preferred in this population
  3. Symptomatic relief of GERD in weeks in 70% of cases
    1. Devault (1999) Am J Gastroenterol 94:1434-42 [PubMed]

VIII. Disadvantages

  1. Even generic costs still approch Proton Pump Inhibitors
    1. (2003) Red Book, Medical Economics Data, Montvale, NJ

IX. Adverse Effects

  1. Common
    1. CNS Effects (Dizziness, Somnolence, Headache)
    2. Nausea
    3. Altered bowel function (Constipation, Diarrhea)
  2. Rare (but serious)
    1. Blood dyscrasia
    2. Hepatotoxicity
    3. Acute Kidney Injury
  3. Ranitidine (Zantac) was removed from U.S. market in 2020 due to NDMA contaminant
    1. NDMA has been associated with several cancers
    2. NDMA was found both as a manufacturing contaminant
    3. NDMA also appears to form in vivo with Ranitidine use
      1. Resulted in the complete withdrawal of Ranitidine from U.S. market
      2. In-vivo NDMA formation does not appear to occur with other H2 Blockers
    4. FDA Recall Information
      1. https://www.fda.gov/drugs/drug-safety-and-availability/fda-updates-and-press-announcements-ndma-zantac-ranitidine
  4. Cimetidine has more Drug Interactions and side effects
  5. Confusion
    1. Avoid H2 Blockers in Cognitive Impairment (Dementia, Delirium)

X. References

  1. (2012) Presc Lett, 19(7): 38

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