II. Background

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

III. Indications

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)

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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Related Studies

Ontology: Methyldopa (C0025741)

Definition (NCI) A phenylalanine derivative and an aromatic amino acid decarboxylase inhibitor with antihypertensive activity. Methyldopa is a prodrug and is metabolized in the central nervous system. The antihypertensive action of methyldopa seems to be attributable to its conversion into alpha-methylnorepinephrine, which is a potent alpha-2 adrenergic agonist that binds to and stimulates potent central inhibitory alpha-2 adrenergic receptors. This results in a decrease in sympathetic outflow and decreased blood pressure.
Definition (MSH) An alpha-2 adrenergic agonist that has both central and peripheral nervous system effects. Its primary clinical use is as an antihypertensive agent.
Concepts Pharmacologic Substance (T121) , Neuroreactive Substance or Biogenic Amine (T124) , Amino Acid, Peptide, or Protein (T116)
MSH D008750
SnomedCT 373542000, 84078002
LNC LP16200-5, MTHU016766
English Alphamethyldopa, alpha Methyl L Dopa, alpha Methyldopa, alpha-Methyl-L-Dopa, alpha-Methyldopa, methyldopa, L-Tyrosine, 3-hydroxy-alpha-methyl-, 3-Hydroxy-alpha-methyl-L-tyrosine, L-2-Amino-2-methyl-3-(3,4-dihydroxyphenyl)propionic Acid, Levo-3-(3,4-Dihydroxyphenyl)-2-methylalanine, O methyl DOPA, methyldopa (medication), Methyldopa [Chemical/Ingredient], alphamethyldopa, alpha-methyldopa, alpha methyldopa, METHYLDOPA, Methyldopa, Alpha methyldopa, Methyldopa (product), Methyldopa (substance)
Swedish Metyldopa
Czech methyldopa
Finnish Metyylidopa
Russian AL'FA-METILDOFA, METILDOPA, METILDOFA, METILDOPAT, АЛЬФА-МЕТИЛДОФА, МЕТИЛДОПА, МЕТИЛДОПАТ, МЕТИЛДОФА
Japanese α-メチルドーパ, メチルドパ, メチルドーパ, アルファ-メチルドーパ
Spanish alfa-Metildopa, metildopa (producto), metildopa (sustancia), metildopato, metildopa, Metildopa
French alpha-Méthyldopa, alpha-L-Méthyldopa, Méthyldopa
Croatian METILDOPA
Polish Metylodopa
German Alphamethyldopa, Methyldopa
Italian Metildopa
Portuguese alfa-Metildopa, Metildopa

Ontology: Aldomet (C0591055)

Concepts Pharmacologic Substance (T121) , Amino Acid, Peptide, or Protein (T116)
MSH D008750
English aldomet, Aldomet, Biopat Brand of Methyldopa, Cahill May Roberts Brand of Methyldopa, Merck Brand of Methyldopa, Merck Sharp & Dohme Brand of Methyldopa, Methyldopa Biopat Brand, Methyldopa Merck Brand