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Methyldopa is a prodrug which is metabolized to the active agent, alpha-methylnorepinephrine.
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Alpha-methylnorepinephrine acts in the brain, inhibiting adrenergic outflow from the brainstem. Inhibition of sympathetic outflow results in a decrease in blood pressure.
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Methyldopa produces no change in cardiac output in younger patients, but in older patients a decline in cardiac output results from reduced heart rate and stroke volume. The reduction in stoke volume occurs due to increased venous pooling (decreased preload).
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Since renal blood flow and function is maintained during methyldopa treatment, methyldopa maybe valuable in managing hypertensive patients with renal insufficiency.
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Adverse Effects:
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Dry Mouth
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Reduced libido
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Parkinsonian signs
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Hyperprolactinemia (gynecomastia, galactorrhea)
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Bradycardia (in patients with SA nodal abnormality)
- Hepatoxicity (avoid in patients with hepatic disease)
- positive Coombs' test (20%)\
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1-5% of those with postive Coombs' develop hemolytic anemia (requiring immediate discontinuation of the drug)
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