Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
APRESAZIDE vs ALDORIL 25
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.
Combination of methyldopa, a centrally acting alpha-2 adrenergic agonist that reduces sympathetic outflow, and hydrochlorothiazide, a thiazide diuretic that inhibits sodium reabsorption in the distal convoluted tubule, reducing plasma volume.
Hypertension
Hypertension
1 capsule (hydralazine 25 mg / hydrochlorothiazide 25 mg) orally twice daily; may increase to 2 capsules twice daily if needed. Maximum: 4 capsules daily.
Oral: 1 tablet (hydrochlorothiazide 25 mg/methyldopa 250 mg) twice daily; increase as needed to max 2 tablets twice daily.
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.
7-16 hours (terminal). In renal impairment, half-life may exceed 24 hours, requiring dose adjustment.
Hydralazine: primarily hepatic acetylation by N-acetyltransferase; Hydrochlorothiazide: not extensively metabolized, eliminated renally.
Methyldopa is metabolized primarily via hepatic conjugation and renal excretion; hydrochlorothiazide is not significantly metabolized and is excreted unchanged in urine.
Hydralazine: ~75% renal (metabolites), <10% unchanged; Hydrochlorothiazide: >95% renal (unchanged).
Renal: ~85% unchanged. Biliary/fecal: ~15% as metabolites.
Hydralazine: 85-90% (plasma proteins); Hydrochlorothiazide: 40-68% (albumin).
Methyldopa: less than 10% bound to plasma proteins. Hydrochlorothiazide: ~70% 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.
Methyldopa: 0.3-0.6 L/kg (distributes widely, including CNS). Hydrochlorothiazide: 0.8-1.5 L/kg (distributes into extracellular fluid).
Hydralazine: 26-50% (oral, first-pass metabolism); Hydrochlorothiazide: 65-70% (oral).
Methyldopa: oral bioavailability ~25% (first-pass metabolism). Hydrochlorothiazide: oral bioavailability ~60-80%.
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 30-50 m L/min: use with caution, reduce dose. GFR <30 m L/min: not recommended.
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 or C: contraindicated due to methyldopa hepatotoxicity risk.
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.
Not established; avoid use in children.
Start with 1 capsule daily; titrate slowly due to increased risk of hypotension and electrolyte imbalance. Monitor renal function and serum potassium.
Start at lowest dose (1 tablet daily); monitor for orthostatic hypotension, sedation, and electrolyte imbalance.
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
May cause sedation, depression, positive direct Coombs test, hemolytic anemia, hepatotoxicity, fluid/electrolyte imbalance, and sensitivity reactions; monitor liver function, CBC, and electrolytes.
Hypersensitivity to hydralazine, hydrochlorothiazide, or sulfonamides,Anuria,Acute myocardial infarction,Dissecting aortic aneurysm,Severe renal impairment (creatinine clearance <30 m L/min)
Hypersensitivity to methyldopa, hydrochlorothiazide, or sulfonamides; active hepatic disease; anuria; history of methyldopa-induced liver disorders.
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 high-sodium foods to optimize antihypertensive effect. Limit alcohol intake. Do not consume large amounts of potassium-rich foods (e.g., bananas, oranges, spinach) unless advised by a healthcare provider, as hydrochlorothiazide can alter potassium levels.
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: Limited human data, but animal studies show no teratogenicity at therapeutic doses. Second and third trimesters: Associated with fetal hypotension, oligohydramnios, and renal dysfunction due to methyldopa component. Hydrochlorothiazide may cause fetal electrolyte imbalances.
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 in breast milk with M/P ratio of approximately 0.2-0.5; hydrochlorothiazide M/P ratio ~0.5-0.6. Considered compatible with breastfeeding by AAP, but monitor infant for hypotension and electrolyte disturbances.
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.
No standard dose adjustment required, but increased plasma volume in pregnancy may necessitate higher doses of methyldopa. Monitor clinical response and adjust accordingly.
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.
ALDORIL 25 is a fixed-dose combination of methyldopa (250 mg) and hydrochlorothiazide (25 mg). Monitor for hypotension, especially during initial therapy or with volume depletion. Methyldopa may cause a positive direct Coombs test and hemolytic anemia; discontinue if anemia develops. Hydrochlorothiazide can cause electrolyte imbalances, hyperglycemia, and hyperuricemia. Avoid use in patients with pheochromocytoma or active liver disease.
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 this medication exactly as prescribed, usually once or twice daily.,Rise slowly from sitting or lying to prevent dizziness from low blood pressure.,Avoid alcohol, which can increase dizziness and drowsiness.,Report any signs of infection, unusual tiredness, or yellowing of skin/eyes.,Use sun protection as hydrochlorothiazide may increase sun sensitivity.,Do not use potassium supplements or salt substitutes 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 ALDORIL 25, 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.. ALDORIL 25 is a Antihypertensive Combination that works by Combination of methyldopa, a centrally acting alpha-2 adrenergic agonist that reduces sympathetic outflow, and hydrochlorothiazide, a thiazide diuretic that inhibits sodium reabsorption in the distal convoluted tubule, reducing plasma volume.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between APRESAZIDE and ALDORIL 25 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 ALDORIL 25 is: Oral: 1 tablet (hydrochlorothiazide 25 mg/methyldopa 250 mg) twice daily; increase as needed to max 2 tablets twice daily.. 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 ALDORIL 25 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. ALDORIL 25 is classified as Category C. First trimester: Limited human data, but animal studies show no teratogenicity at therapeutic doses. Second and third trimesters: Associated with fetal hypotension, oligohydramnios. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.