Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
APRESAZIDE vs ALDOMET
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Apresazide is a combination of hydralazine, a direct-acting vasodilator that relaxes arteriolar smooth muscle, and hydrochlorothiazide, a thiazide diuretic that inhibits sodium and chloride reabsorption in the distal convoluted tubule.
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
Hypertension (first-line in pregnancy-induced hypertension),Off-label: treatment of hypertensive crises
1 capsule (hydralazine 25 mg / hydrochlorothiazide 25 mg) orally twice daily; may increase to 2 capsules twice daily if needed. Maximum: 4 capsules daily.
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.
Hydralazine: 2-4 hours (fast acetylators), 4-8 hours (slow acetylators); Hydrochlorothiazide: 6-15 hours. Clinical context: Dosing interval typically 12 hours for hydralazine component.
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.
Hydralazine: primarily hepatic acetylation by N-acetyltransferase; Hydrochlorothiazide: not extensively metabolized, eliminated renally.
Primarily hepatic metabolism via conjugation and O-methylation; also undergoes decarboxylation and deamination. Active metabolites include alpha-methyldopamine and alpha-methylnorepinephrine.
Hydralazine: ~75% renal (metabolites), <10% unchanged; Hydrochlorothiazide: >95% renal (unchanged).
Renal: ~70% as unchanged drug and metabolites (sulfate conjugate, O-methylated derivatives); fecal/biliary: ~20%; <5% removed by hemodialysis.
Hydralazine: 85-90% (plasma proteins); Hydrochlorothiazide: 40-68% (albumin).
~10-20% bound to plasma proteins (primarily albumin).
Hydralazine: 1.5 L/kg; Hydrochlorothiazide: 3-4 L/kg. Clinical meaning: Hydralazine distributes widely; Hydrochlorothiazide distributes into extracellular fluid.
0.2–0.4 L/kg; clinical meaning: Moderate distribution, indicating limited extravascular penetration.
Hydralazine: 26-50% (oral, first-pass metabolism); Hydrochlorothiazide: 65-70% (oral).
Oral: ~50% (range 25-60%) due to first-pass metabolism; IV: 100%.
Contraindicated in anuria. For GFR 30-50 m L/min: reduce dose to 1 capsule daily. For GFR <30 m L/min: avoid use due to thiazide inefficacy.
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 A: no adjustment. Child-Pugh B: reduce dose by 50% (start with 1 capsule daily). Child-Pugh C: contraindicated.
Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid use or reduce dose by 75%.
Weight-based: hydralazine 0.75-1 mg/kg/dose every 6-12 hours (max 50 mg/dose); hydrochlorothiazide 1-2 mg/kg/day divided every 12 hours. Combination not recommended; adjust individual components.
10 mg/kg/day orally in 2-4 divided doses, increased gradually; maximum 65 mg/kg/day or 3 g/day.
Start with 1 capsule daily; titrate slowly due to increased risk of hypotension and electrolyte imbalance. Monitor renal function and serum potassium.
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 (hydralazine),Peripheral neuritis (hydralazine),Electrolyte imbalances (hypokalemia, hyponatremia) due to hydrochlorothiazide,Sulfonamide hypersensitivity cross-reaction,Exacerbation or activation of systemic lupus erythematosus,Possible myocardial infarction or angina pectoris in patients with coronary artery disease
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, hydrochlorothiazide, or sulfonamides,Anuria,Acute myocardial infarction,Dissecting aortic aneurysm,Severe renal impairment (creatinine clearance <30 m L/min)
Active hepatic disease (acute hepatitis, cirrhosis); prior methyldopa-induced hepatic dysfunction; concurrent MAO inhibitor therapy; hypersensitivity to methyldopa; pheochromocytoma.
Avoid high-potassium foods if potassium-sparing effect is not desired (but hydrochlorothiazide causes potassium loss; monitor accordingly). Take with food to reduce GI upset. Avoid natural licorice as it may enhance potassium loss and worsen hypertension.
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.
Apresazide is a fixed-dose combination of hydralazine and hydrochlorothiazide. Hydralazine: First trimester: limited data, no clear evidence of major malformations; second and third trimesters: risk of neonatal thrombocytopenia, lupus-like syndrome, and hypotension. Hydrochlorothiazide: First trimester: possible association with neural tube defects and oral clefts (weak); second and third trimesters: fetal or neonatal jaundice, thrombocytopenia, electrolyte imbalance, and possible growth restriction. Overall, use only if benefit outweighs 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.
Hydralazine: excreted in breast milk in low amounts; M/P ratio not well established; considered compatible with caution. Hydrochlorothiazide: excreted in breast milk; may suppress lactation; risk of neonatal electrolyte disturbances. Avoid use during breastfeeding, especially with high doses.
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.
Hydralazine: dose may need downward adjustment in later pregnancy due to altered volume of distribution and increased clearance. Hydrochlorothiazide: avoid use in pregnancy; consider alternative diuretics. If used, dose adjustment not well defined but start at lowest effective dose. No standard pharmacokinetic-based adjustments.
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.
Combination product of hydralazine and hydrochlorothiazide. Monitor for lupus-like syndrome (especially with high hydralazine doses). Check electrolytes and renal function regularly. Use with caution in patients with coronary artery disease or high-output heart failure.
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 skip doses.,May cause dizziness or faintness, especially when rising from sitting or lying position.,Avoid sudden discontinuation; taper under medical supervision.,Report symptoms like joint pain, fever, chest pain, or rash immediately.,Limit alcohol intake as it can exacerbate hypotension.
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 APRESAZIDE vs ALDOMET, answered by our medical review team.
APRESAZIDE is a Antihypertensive that works by Apresazide is a combination of hydralazine, a direct-acting vasodilator that relaxes arteriolar smooth muscle, and hydrochlorothiazide, a thiazide diuretic that inhibits sodium and chloride reabsorption in the distal convoluted tubule.. 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 APRESAZIDE 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 APRESAZIDE is: 1 capsule (hydralazine 25 mg / hydrochlorothiazide 25 mg) orally twice daily; may increase to 2 capsules twice daily if needed. Maximum: 4 capsules daily.. 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 APRESAZIDE 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. APRESAZIDE is classified as Category C. Apresazide is a fixed-dose combination of hydralazine and hydrochlorothiazide. Hydralazine: First trimester: limited data, no clear evidence of major malformations; second and thir. 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.