Methyl-Dopa

Aka: Methyl-Dopa, Methyldopa, Alpha Methyldopa, Aldomet

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II. Background

  1. As of 2021, methydopa is unavailable in U.S., and production has been discontinued

III. Indications

  1. Hypertension in Pregnancy

IV. Safety

  1. Safe in Lactation
  2. Pregnancy Category B
    1. Long safety record in pregnancy

V. Contraindications

  1. Significant Liver Disease

VI. Mechanism

  1. See Alpha Adrenergic Central Agonist
  2. See Alpha Adrenergic Receptor
  3. Central Acting Adrenergic Agonist
    1. Activates alpha-2 receptors that inhibit CNS sympathetic signals (similar to Clonidine)
    2. Results in increased parasympathetic effects and side effects
  4. Methylnorepinephrine (Methyldopa) metabolite
    1. Weak Sympathomimetic that also decreases CNS sympathetic outflow

VII. Pharmacokinetics

  1. Methyldopa is metabolized via alpha-methyl Dopamine to alpha-methylnorepinephrine (central alpha-2 Agonist)
  2. Renal excretion (metabolized or 63% as unchanged in urine)

VIII. Dosing: Hypertension in Pregnancy

  1. Start: 250 mg orally twice to three times daily
  2. Maintenance: 500 mg orally twice daily
  3. Maximum: Up to 3000 mg daily in divided doses

IX. Dosing: Hypertensive Crisis

  1. Start: 250-500 mg IV every 6 hours (up to 1000 mg every 6 hours)

X. Dosing: Pediatric Hypertension

  1. Dose: 10 mg/kg/day divided bid to qid
  2. Maximum: 65 mg/kg/day up to 3000 mg/day in divided doses

XI. Disadvantages

  1. As of 2021, methydopa is unavailable in U.S., and production has been discontinued
  2. Weak Antihypertensive
  3. Less tolerated (Fatigue, Dizziness) than other agents

XII. Adverse Effects

  1. See Alpha Adrenergic Central Agonist
  2. Somnolence
  3. Dry Mouth
  4. Orthostatic Hypotension or Dizziness
  5. Nasal congestion
  6. Erectile Dysfunction
  7. Nightmares
  8. Involuntary movements
  9. Hepatotoxicity
  10. Sodium and water retention
    1. Reflex renin release in response to excessive Clonidine and renal hypoperfusion
    2. Discontinue for Congestive Heart Failure signs
  11. Hemolytic Anemia (rare, serious)
    1. Coombs positive
    2. Monitor Complete Blood Count

XIII. Drug Interactions

  1. Tricyclic Antidepressants
    1. Decreased clonidine Antihypertensive effect
  2. CNS Depressants (e.g. Alcohol, Benzodiazepines, Barbiturates)
    1. Increase Clonidine related CNS effects (e.g. Somnolence)

XIV. Resources

  1. Methydopa (DailyMed)
    1. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c8bea68b-3932-4538-b568-a296a8817291

XV. References

  1. (2020) Med Lett Drugs Ther 62(1598): 73-80
  2. Olson (2020) Clinical Pharmacology, MedMaster, Miami, p. 64-5
  3. Hamilton (2010) Tarascon Pocket Pharmacopeia, Jones and Bartlett, p. 76

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