Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
APRESAZIDE vs ALDORIL 15
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 that reduces sympathetic outflow from the brainstem, decreasing peripheral vascular resistance and blood pressure. Hydrochlorothiazide is a thiazide diuretic that inhibits sodium and chloride reabsorption in the distal convoluted tubule, reducing plasma volume and cardiac output.
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.
1 tablet (hydrochlorothiazide 15 mg, methyldopa 250 mg) orally twice daily; increase as needed up to 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.
Terminal half-life: 12–17 hours; clinical context: steady-state achieved within 2–3 days; effect persists 12–24 hours
Hydralazine: primarily hepatic acetylation by N-acetyltransferase; Hydrochlorothiazide: not extensively metabolized, eliminated renally.
Methyldopa is metabolized in the liver via conjugation and O-methylation; active metabolites include methyldopamine and methylnorepinephrine. Hydrochlorothiazide is not significantly metabolized and is excreted unchanged in urine.
Hydralazine: ~75% renal (metabolites), <10% unchanged; Hydrochlorothiazide: >95% renal (unchanged).
Renal: ~70% unchanged; biliary/fecal: ~30% as metabolites
Hydralazine: 85-90% (plasma proteins); Hydrochlorothiazide: 40-68% (albumin).
~90%, primarily to albumin
Hydralazine: 1.5 L/kg; Hydrochlorothiazide: 3-4 L/kg. Clinical meaning: Hydralazine distributes widely; Hydrochlorothiazide distributes into extracellular fluid.
2–4 L/kg; clinical meaning: extensive tissue distribution, concentrating in vascular smooth muscle
Hydralazine: 26-50% (oral, first-pass metabolism); Hydrochlorothiazide: 65-70% (oral).
Oral: 50–60% (extensive first-pass metabolism)
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: maximum 1 tablet twice daily. GFR <30 m L/min: avoid use.
Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 50% (start with 1 capsule daily). Child-Pugh C: contraindicated.
Child-Pugh A: caution, reduce dose. Child-Pugh B: avoid. Child-Pugh C: contraindicated.
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 recommended for pediatric use; safety in children under 12 years not established.
Start with 1 capsule daily; titrate slowly due to increased risk of hypotension and electrolyte imbalance. Monitor renal function and serum potassium.
Start with 1 tablet once daily; monitor for hypotension and electrolyte imbalance. Reduce initial dose by 50%.
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
Sedation, usually transient; may impair ability to drive or operate heavy machinery.,Positive Coombs test with hemolytic anemia (rare); monitor hematocrit and Coombs test.,Hepatotoxicity (hepatic necrosis) with fever, jaundice; discontinue if liver abnormalities occur.,Fluid and electrolyte imbalance (hypokalemia, hyponatremia, hypercalcemia) due to thiazide.,May precipitate gout in hyperuricemic patients.,May exacerbate systemic lupus erythematosus.
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 (e.g., acute hepatitis, cirrhosis),Prior methyldopa therapy associated with liver disorders,Hypersensitivity to methyldopa or hydrochlorothiazide,Anuria,Sulfonamide allergy (cross-sensitivity with thiazides)
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 as they can reduce antihypertensive efficacy. Thiazides may cause hypokalemia; increase dietary potassium (bananas, orange juice) unless contraindicated. Alcohol may enhance orthostatic hypotension.
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 malformations based on limited human data; animal studies show no teratogenicity at clinically relevant doses. Second/third trimesters: Fetal and neonatal adverse effects including oligohydramnios, fetal renal dysfunction, skull ossification delay, and hypotension in the neonate. Avoid use after 20 weeks gestation unless no alternative.
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 and hydrochlorothiazide are excreted into human milk. M/P ratio for methyldopa is approximately 0.5-1.0; for hydrochlorothiazide, M/P ratio ~2.0. Methyldopa is considered compatible with breastfeeding. Hydrochlorothiazide may suppress lactation and cause neonatal electrolyte disturbances. Use with caution; monitor infant for signs of diuresis or electrolyte imbalance.
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.
Pharmacokinetic changes in pregnancy may include increased volume of distribution and enhanced renal clearance. No specific dose adjustment routine is recommended; dosing should be guided by clinical response. Methyldopa starting dose 250 mg twice daily, titrated to effect. Hydrochlorothiazide dose not typically adjusted, but caution due to potential volume depletion.
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 15 (methyldopa 250mg + hydrochlorothiazide 15mg) is rarely used due to superior alternatives. Monitor for hepatotoxicity, hemolytic anemia, and lupus-like syndrome. Titrate slowly to avoid sedation. Contraindicated in active liver disease, pheochromocytoma, and anuria.
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.
May cause drowsiness; avoid driving until tolerance develops.,Report unexplained fever, jaundice, or dark urine immediately.,Take at bedtime to minimize sedation.,Avoid sudden discontinuation; follow prescribed tapering schedule.,Use sun protection; thiazides increase photosensitivity.
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 15, 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 15 is a Antihypertensive Combination that works by Methyldopa is a centrally acting alpha-2 adrenergic agonist that reduces sympathetic outflow from the brainstem, decreasing peripheral vascular resistance and blood pressure. Hydrochlorothiazide is a thiazide diuretic that inhibits sodium and chloride reabsorption in the distal convoluted tubule, reducing plasma volume and cardiac output.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between APRESAZIDE and ALDORIL 15 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 15 is: 1 tablet (hydrochlorothiazide 15 mg, methyldopa 250 mg) orally twice daily; increase as needed up to 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 15 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 15 is classified as Category C. First trimester: No increased risk of major malformations based on limited human data; animal studies show no teratogenicity at clinically relevant doses. Second/third trimesters: . Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.