Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
APRESOLINE vs ALDOMET
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Direct-acting arteriolar vasodilator that relaxes vascular smooth muscle, leading to decreased peripheral resistance and blood pressure. The exact molecular mechanism is unclear but may involve interference with calcium movement or inhibition of inositol trisphosphate-induced calcium release.
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.
Hypertension (oral, as adjunctive therapy),Severe hypertension or hypertensive emergency (parenteral)
Hypertension (first-line in pregnancy-induced hypertension),Off-label: treatment of hypertensive crises
Initial: 10 mg oral 4 times daily for 2-4 days; increase to 25 mg 4 times daily for the first week. Maintenance: 50 mg 4 times daily; maximum 300 mg/day. IV: 20-40 mg IM or slow IV push, repeat as needed.
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.
Terminal elimination half-life is 3-7 hours in patients with normal renal function; prolonged to 7-16 hours in renal impairment. Acetylator phenotype affects half-life: in slow acetylators, half-life may be 4-5 hours; in fast acetylators, 1-2 hours, but clinical effect (antihypertensive) lasts longer due to persistent binding to vascular tissue.
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.
Extensively metabolized in the liver via acetylation (N-acetyltransferase, NAT2) and oxidation (CYP450, primarily CYP3A4 and CYP2C19).
Primarily hepatic metabolism via conjugation and O-methylation; also undergoes decarboxylation and deamination. Active metabolites include alpha-methyldopamine and alpha-methylnorepinephrine.
Primarily renal; 86-90% of an oral dose is excreted in urine as metabolites (N-acetylhydralazine, hydralazine pyruvic acid hydrazone) and unchanged drug (<10% unchanged); biliary/fecal excretion is minimal (<10%).
Renal: ~70% as unchanged drug and metabolites (sulfate conjugate, O-methylated derivatives); fecal/biliary: ~20%; <5% removed by hemodialysis.
87-90% bound to plasma proteins, primarily albumin; binding is reduced in uremia.
~10-20% bound to plasma proteins (primarily albumin).
1.5-1.8 L/kg; distributes widely into total body water, with high affinity for vascular smooth muscle, where it accumulates; Vd is larger in slow acetylators due to higher free drug levels.
0.2–0.4 L/kg; clinical meaning: Moderate distribution, indicating limited extravascular penetration.
Oral immediate-release: 30-50% in fast acetylators; 50-75% in slow acetylators. Bioavailability is increased when taken with food (peak concentration enhanced 50-70%).
Oral: ~50% (range 25-60%) due to first-pass metabolism; IV: 100%.
Cr Cl 10-50 m L/min: administer every 8 hours. Cr Cl <10 m L/min: administer every 8 hours or reduce dose by 50%.
GFR >50 m L/min: no adjustment; GFR 10-50 m L/min: interval every 12-24 hours; GFR <10 m L/min: interval every 24-48 hours or 250 mg every 36-48 hours.
Child-Pugh Class B: reduce dose by 50%. Child-Pugh Class C: avoid use or reduce dose by 75%.
Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid use or reduce dose by 75%.
Oral: 0.75-3 mg/kg/day in 2-4 divided doses, maximum 7.5 mg/kg/day or 200 mg/day. IV: 0.1-0.2 mg/kg/dose every 4-6 hours as needed.
10 mg/kg/day orally in 2-4 divided doses, increased gradually; maximum 65 mg/kg/day or 3 g/day.
Start at 10 mg 2-3 times daily; increase gradually to avoid hypotension. Maximum 200 mg/day. Monitor for orthostatic hypotension and reflex tachycardia.
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.
None.
None
May cause drug-induced lupus erythematosus, especially in slow acetylators; monitor for symptoms. Use cautiously in patients with coronary artery disease (may cause reflex tachycardia and exacerbate angina). Can cause peripheral neuritis (pyridoxine deficiency), alone with high doses. May cause sodium and water retention, requiring concomitant diuretic therapy.
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.
Hypersensitivity to hydralazine or any component of the formulation. Mitral valve rheumatic heart disease. Aortic aneurysm (theoretical contraindication due to increased cardiac output/loading conditions).
Active hepatic disease (acute hepatitis, cirrhosis); prior methyldopa-induced hepatic dysfunction; concurrent MAO inhibitor therapy; hypersensitivity to methyldopa; pheochromocytoma.
Food may increase bioavailability of hydralazine; take with food to reduce peak concentrations and potential side effects. Avoid tyramine-rich foods (e.g., aged cheeses, cured meats) if taking MAOIs concurrently. No specific dietary restrictions otherwise.
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.
First trimester: Limited human data; animal studies show no teratogenicity at clinically relevant doses, but risk cannot be excluded. Second and third trimesters: May cause fetal tachycardia, neonatal hypotension, and ileus; associated with maternal hypotension and potential uteroplacental insufficiency. FDA Pregnancy Category C.
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.
Minimal excretion into breast milk; M/P ratio approximately 1.0. Considered compatible with breastfeeding by the American Academy of Pediatrics; monitor infant for hypotension and feeding difficulties.
Methyldopa is excreted into breast milk in small amounts (M/P ratio approximately 0.2-0.5). At typical maternal doses, infant exposure is likely subtherapeutic and considered compatible with breastfeeding. Monitor infant for potential hypotension or sedation.
No standard dose adjustment recommended; however, increased plasma volume may necessitate higher doses. Monitor response and titrate to effect; avoid severe hypotension to prevent uteroplacental hypoperfusion.
Pregnancy may increase volume of distribution and renal clearance, potentially reducing methyldopa plasma concentrations. Dose adjustments may be necessary to maintain blood pressure control; monitor and titrate based on maternal blood pressure response. Typical starting dose: 250 mg orally twice daily; maximum up to 3 g/day in divided doses, but lower doses are often effective.
Hydralazine (Apresoline) is a direct-acting vasodilator primarily used for hypertension management, especially in preeclampsia and hypertensive emergencies. It can cause a lupus-like syndrome, especially in slow acetylators; testing for N-acetyltransferase 2 (NAT2) phenotype may be considered. Tachyphylaxis can occur; concomitant beta-blocker and diuretic therapy are often required. Onset of action is 10-20 minutes IV, 20-30 minutes IM. Avoid in patients with coronary artery disease due to reflex tachycardia.
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.
Take exactly as prescribed; do not stop suddenly as this can cause a rapid rise in blood pressure.,May cause dizziness or lightheadedness; avoid driving or operating machinery until you know how this medicine affects you.,Report any unexplained joint pain, fever, chest pain, or rash to your doctor immediately as these may be signs of a serious reaction (drug-induced lupus).,Avoid alcohol consumption as it can increase the blood pressure lowering effects and dizziness.,Do not take over-the-counter cold, sinus, or weight loss products without checking with your doctor, as many contain ingredients that can raise blood pressure.
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.
No interactions on record
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about APRESOLINE vs ALDOMET, answered by our medical review team.
APRESOLINE is a Antihypertensive that works by Direct-acting arteriolar vasodilator that relaxes vascular smooth muscle, leading to decreased peripheral resistance and blood pressure. The exact molecular mechanism is unclear but may involve interference with calcium movement or inhibition of inositol trisphosphate-induced calcium release.. ALDOMET is a Central Alpha Agonist Antihypertensive that works by 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.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between APRESOLINE and ALDOMET depend on the specific clinical indication. These are agents from distinct pharmacological classes and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of APRESOLINE is: Initial: 10 mg oral 4 times daily for 2-4 days; increase to 25 mg 4 times daily for the first week. Maintenance: 50 mg 4 times daily; maximum 300 mg/day. IV: 20-40 mg IM or slow IV push, repeat as needed.. The standard adult dose of ALDOMET is: 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.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between APRESOLINE and ALDOMET in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. APRESOLINE is classified as Category C. First trimester: Limited human data; animal studies show no teratogenicity at clinically relevant doses, but risk cannot be excluded. Second and third trimesters: May cause fetal t. ALDOMET is classified as Category C. 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 . Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.