Nurses Compass
Drug Guide
Methyldopa
Classification
Therapeutic: Antihypertensive
Pharmacological: Central alpha-2 adrenergic agonist
FDA Approved Indications
- Management of hypertension, especially in pregnant women
Mechanism of Action
Methyldopa is converted in the central nervous system to alpha-methyl norepinephrine, which stimulates central alpha-2 adrenergic receptors, reducing sympathetic outflow and thereby decreasing blood pressure.
Dosage and Administration
Adult: Initial dose: 250 mg 2-3 times daily; titrate gradually up to a total of 1,000 mg/day in divided doses as needed and tolerated.
Pediatric: Dosage varies depending on weight and clinical response; consult pediatric dosing guidelines.
Geriatric: Start at lower doses; monitor closely due to increased susceptibility to hypotension and CNS effects.
Renal Impairment: Adjust dose based on renal function; closely monitor blood pressure.
Hepatic Impairment: Use with caution; no specific dose adjustment established.
Pharmacokinetics
Absorption: Well absorbed orally.
Distribution: Widely distributed, crosses the blood-brain barrier.
Metabolism: Partially metabolized in the liver.
Excretion: Excreted primarily in the urine, both as unchanged drug and metabolites.
Half Life: Approximately 2-3 hours.
Contraindications
- Hypersensitivity to methyldopa or its components.
- History of hepatic disease or existing abnormal liver function.
Precautions
- Use with caution in patients with renal impairment, cerebrovascular disease, or history of depression. Monitor liver function regularly.
- Pregnancy category B; generally considered safe in pregnancy but monitor hepatic function.
Adverse Reactions - Common
- Sedation, fatigue (Common)
- Dizziness, orthostatic hypotension (Common)
- Dry mouth, nasal congestion (Common)
Adverse Reactions - Serious
- Hepatotoxicity, including hepatitis and liver failure (Rare)
- Hemolytic anemia (Rare)
- Positive Coombs test (Rare)
- Fluid retention, lupus erythematosus-like syndrome (Rare)
Drug-Drug Interactions
- MAO inhibitors (risk of hypertensive crisis), other antihypertensives (additive effect)
- Certain antidepressants
Drug-Food Interactions
N/ADrug-Herb Interactions
N/ANursing Implications
Assessment: Monitor blood pressure regularly; assess for signs of liver dysfunction (jaundice, dark urine); assess mental status.
Diagnoses:
- Risk for hypotension
- Impaired liver function
Implementation: Administer doses with food to reduce gastrointestinal upset; titrate dose carefully; monitor blood pressure and liver function tests periodically.
Evaluation: Assess for effectiveness in blood pressure control; monitor for adverse effects, especially hepatotoxicity.
Patient/Family Teaching
- Take medication exactly as prescribed.
- Report symptoms of liver problems (jaundice, dark urine), mental changes, or signs of allergic reactions.
- Avoid abrupt discontinuation to prevent hypertensive crisis.
- Monitor blood pressure regularly at home.
Special Considerations
Black Box Warnings:
- Hepatotoxicity; discontinue if signs of liver dysfunction occur.
Genetic Factors: None established.
Lab Test Interference: Can cause a positive Coombs test, which may indicate hemolytic anemia.
Overdose Management
Signs/Symptoms: Hypotension, bradycardia, sedation, respiratory depression in severe cases.
Treatment: Supportive care, discontinue drug, monitor vital signs, and provide symptomatic treatment.
Storage and Handling
Storage: Store in a tightly closed container at room temperature, away from heat and moisture.
Stability: Stable under recommended storage conditions.