ALDOMET
Clinical safety rating
cautionComprehensive clinical and safety monograph for ALDOMET (ALDOMET).
Methyldopa is a centrally acting alpha-2 adrenergic agonist. Its active metabolite, alpha-methylnorepinephrine, stimulates presynaptic alpha-2 receptors in the central nervous system, reducing sympathetic outflow from the brainstem and decreasing peripheral vascular resistance, leading to lowered blood pressure.
| Metabolism | Primarily hepatic metabolism via conjugation and O-methylation; also undergoes decarboxylation and deamination. Active metabolites include alpha-methyldopamine and alpha-methylnorepinephrine. |
| Excretion | Renal: ~70% as unchanged drug and metabolites (sulfate conjugate, O-methylated derivatives); fecal/biliary: ~20%; <5% removed by hemodialysis. |
| Half-life | 1.5–2 hours (terminal elimination half-life); clinical context: Renal impairment prolongs half-life (up to 4–6 hours in severe impairment), necessitating dose adjustment. |
| Protein binding | ~10-20% bound to plasma proteins (primarily albumin). |
| Volume of Distribution | 0.2–0.4 L/kg; clinical meaning: Moderate distribution, indicating limited extravascular penetration. |
| Bioavailability | Oral: ~50% (range 25-60%) due to first-pass metabolism; IV: 100%. |
| Onset of Action | Oral: 3–6 hours for maximal antihypertensive effect; IV: 2–3 hours for parenteral route. |
| Duration of Action | Oral: 24–48 hours (single dose); sustained effect with repeated dosing; clinical note: Full antihypertensive effect may not be seen for 2–3 days. |
| Molecular Weight | 238.25 |
250 mg orally twice daily, increased as needed every 2-3 days; usual maintenance 500 mg to 2 g/day in 2-4 divided doses; maximum 3 g/day.
| Dosage form | SUSPENSION |
| Renal impairment | GFR >50 mL/min: no adjustment; GFR 10-50 mL/min: interval every 12-24 hours; GFR <10 mL/min: interval every 24-48 hours or 250 mg every 36-48 hours. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid use or reduce dose by 75%. |
| Pediatric use | 10 mg/kg/day orally in 2-4 divided doses, increased gradually; maximum 65 mg/kg/day or 3 g/day. |
| Geriatric use | Initial dose 250 mg once or twice daily; increase slowly; monitor for hypotension, sedation, and bradycardia; avoid in patients with pre-existing bradycardia or heart block. |
| 1st trimester | Use only if clearly needed. Methyldopa is generally considered safe in pregnancy for chronic hypertension. Avoid in second half of pregnancy due to increased risk of maternal hepatotoxicity. |
| 2nd trimester | Generally considered safe; monitor liver function. Avoid in patients with liver disease. |
| 3rd trimester | Generally considered safe; may cause mild hypotension in neonate. Monitor for maternal hepatotoxicity. |
Clinical note
Comprehensive clinical and safety monograph for ALDOMET (ALDOMET).
| Placental transfer | Crosses placenta; fetal serum levels similar to maternal levels. |
| Breastfeeding | Methyldopa is excreted into breast milk in small amounts (0.02% of maternal dose). No adverse effects reported in infants. Considered compatible with breastfeeding by the American Academy of Pediatrics. |
| Lactation Rating | L2 (Probably Compatible) |
| Teratogenic Risk | First trimester: No increased risk of major congenital malformations reported in human studies based on limited data. Second and third trimesters: No known teratogenicity; use for management of chronic hypertension in pregnancy is common, but consider potential for reduced placental perfusion if maternal blood pressure is excessively lowered. |
| Fetal Monitoring | Maternal: Blood pressure, CBC (due to risk of hemolytic anemia), liver function tests, and Coombs test (direct and indirect) periodically. Fetal: Fetal heart rate and growth monitoring via ultrasound if used in pregnancy hypertension. |
| Fertility Effects | No known adverse effects on fertility in males or females based on available data. |
■ FDA Black Box Warning
None
| Serious Effects |
Active liver disease, such as acute hepatitis or active cirrhosisHistory of hepatic impairment associated with previous methyldopa therapyHypersensitivity to methyldopa or any component
| Precautions | Hepatic toxicity (fatal hepatic necrosis reported); hemolytic anemia (positive Coombs test common, may indicate hemolysis); sedation/drowsiness (impair mental alertness); orthostatic hypotension; caution in renal impairment (dose adjustment required); may cause positive direct Coombs test, which interferes with crossmatching; possible rebound hypertension upon abrupt discontinuation. |
| Food/Dietary | Avoid excessive sodium intake, as it can counteract the antihypertensive effect. No specific food interactions reported, but alcohol may potentiate hypotension and sedation. Iron supplements may reduce absorption of methyldopa; separate administration by at least 2 hours. |
| Clinical Pearls | ALDOMET (methyldopa) is a centrally acting alpha-2 agonist used primarily for hypertension in pregnancy. Monitor for positive direct Coombs test, which can occur in up to 20% of patients on long-term therapy; this may interfere with cross-matching but rarely causes hemolysis. Hepatic adverse effects, including increased liver enzymes and rarely hepatitis, require monitoring. Sedation and dizziness are common initially; titrate dose slowly. Methyldopa may cause orthostatic hypotension; advise patients to rise slowly. A paradoxical pressor response may occur if given with MAO inhibitors. |
| Patient Advice | Take exactly as prescribed; do not skip doses or stop suddenly as this may cause rebound hypertension. · This medication may cause drowsiness, especially at start of therapy; avoid driving or operating machinery until you know how it affects you. · Rise slowly from sitting or lying positions to minimize dizziness or fainting. · Report any unexplained fever, fatigue, jaundice (yellowing of skin/eyes), or dark urine to your healthcare provider immediately, as these may indicate liver problems. · Notify your doctor if you experience persistent dry mouth, flu-like symptoms, or swelling in the legs. · Regular blood pressure monitoring is essential; keep a log of readings. · Avoid alcohol, as it can increase drowsiness and lower blood pressure further. · Inform all healthcare providers, including dentists, that you are taking this medication. · Do not take any other medications, including over-the-counter products, without consulting your doctor. |
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