Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
APRESOLINE 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
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.
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 (oral, as adjunctive therapy),Severe hypertension or hypertensive emergency (parenteral)
Hypertension
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.
Oral: 1 tablet (hydrochlorothiazide 25 mg/methyldopa 250 mg) twice daily; increase as needed to max 2 tablets twice daily.
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.
7-16 hours (terminal). In renal impairment, half-life may exceed 24 hours, requiring dose adjustment.
Extensively metabolized in the liver via acetylation (N-acetyltransferase, NAT2) and oxidation (CYP450, primarily CYP3A4 and CYP2C19).
Methyldopa is metabolized primarily via hepatic conjugation and renal excretion; hydrochlorothiazide is not significantly metabolized and is excreted unchanged in urine.
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: ~85% unchanged. Biliary/fecal: ~15% as metabolites.
87-90% bound to plasma proteins, primarily albumin; binding is reduced in uremia.
Methyldopa: less than 10% bound to plasma proteins. Hydrochlorothiazide: ~70% 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.
Methyldopa: 0.3-0.6 L/kg (distributes widely, including CNS). Hydrochlorothiazide: 0.8-1.5 L/kg (distributes into extracellular fluid).
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%).
Methyldopa: oral bioavailability ~25% (first-pass metabolism). Hydrochlorothiazide: oral bioavailability ~60-80%.
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 30-50 m L/min: use with caution, reduce dose. GFR <30 m L/min: not recommended.
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 or C: contraindicated due to methyldopa hepatotoxicity risk.
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.
Not established; avoid use in children.
Start at 10 mg 2-3 times daily; increase gradually to avoid hypotension. Maximum 200 mg/day. Monitor for orthostatic hypotension and reflex tachycardia.
Start at lowest dose (1 tablet daily); monitor for orthostatic hypotension, sedation, and electrolyte imbalance.
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.
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 or any component of the formulation. Mitral valve rheumatic heart disease. Aortic aneurysm (theoretical contraindication due to increased cardiac output/loading conditions).
Hypersensitivity to methyldopa, hydrochlorothiazide, or sulfonamides; active hepatic disease; anuria; history of methyldopa-induced liver disorders.
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 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.
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: 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.
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 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.
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.
No standard dose adjustment required, but increased plasma volume in pregnancy may necessitate higher doses of methyldopa. Monitor clinical response and adjust accordingly.
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.
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 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 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 APRESOLINE vs ALDORIL 25, 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.. 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 APRESOLINE 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 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 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 APRESOLINE 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. 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. 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.