Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
HYDRA-ZIDE 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
Hydra-Zide is a combination of hydrochlorothiazide (thiazide diuretic) and hydralazine (direct vasodilator). Hydrochlorothiazide inhibits the sodium-chloride symporter in the distal convoluted tubule, reducing electrolyte reabsorption and increasing urine output. Hydralazine relaxes arteriolar smooth muscle, decreasing systemic vascular resistance and afterload.
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.
Treatment of hypertension
Hypertension
Oral, 1 tablet (25 mg hydrochlorothiazide / 50 mg hydralazine) twice daily, titrated up to maximum of 2 tablets twice daily based on blood pressure response.
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); thiazide: 6-15 hours.
7-16 hours (terminal). In renal impairment, half-life may exceed 24 hours, requiring dose adjustment.
Hydrochlorothiazide is not extensively metabolized; eliminated unchanged primarily by renal tubular secretion. Hydralazine undergoes extensive hepatic metabolism via acetylation (N-acetyltransferase) and hydroxylation, with glucuronidation and sulfation.
Methyldopa is metabolized primarily via hepatic conjugation and renal excretion; hydrochlorothiazide is not significantly metabolized and is excreted unchanged in urine.
Renal: 50-70% of hydralazine as metabolites, 30-40% as parent drug; thiazide: 95% renal as unchanged drug.
Renal: ~85% unchanged. Biliary/fecal: ~15% as metabolites.
Hydralazine: 85-90% bound to albumin; thiazide: 40-70% bound to albumin.
Methyldopa: less than 10% bound to plasma proteins. Hydrochlorothiazide: ~70% bound to plasma proteins (primarily albumin).
Hydralazine: 1.5-2.5 L/kg (distributes extensively into tissues); thiazide: 0.2-0.5 L/kg (primarily 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: 30-50% (oral, variable due to first-pass metabolism); thiazide: 60-80% (oral).
Methyldopa: oral bioavailability ~25% (first-pass metabolism). Hydrochlorothiazide: oral bioavailability ~60-80%.
GFR >30 m L/min: No adjustment. GFR 10-30 m L/min: Use with caution, consider reducing dose (e.g., 1 tablet once daily) or extending interval; avoid if possible. GFR <10 m L/min: Not recommended due to thiazide ineffectiveness.
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: Consider 50% dose reduction (e.g., 1 tablet once daily) and monitor liver function. Child-Pugh C: Contraindicated due to risk of hepatic encephalopathy and hydralazine accumulation.
Child-Pugh A: no adjustment; Child-Pugh B or C: contraindicated due to methyldopa hepatotoxicity risk.
Not approved for pediatric use; safety and efficacy not established. Alternative antihypertensives preferred.
Not established; avoid use in children.
Start at 0.5 tablet (12.5 mg hydrochlorothiazide / 25 mg hydralazine) once or twice daily; titrate slowly. Monitor for hypotension, electrolyte disturbances, and renal function. Maximum dose 2 tablets daily.
Start at lowest dose (1 tablet daily); monitor for orthostatic hypotension, sedation, and electrolyte imbalance.
There is no FDA black box warning for Hydra-Zide.
None
May cause a lupus-like syndrome, especially in slow acetylators; discontinue if symptoms appear.,Risk of hypotension, especially with high doses or volume depletion.,Can cause electrolyte imbalances (hypokalemia, hyponatremia, hypercalcemia), monitor serum electrolytes.,May exacerbate renal impairment; use with caution in renal disease.,Possible hypersensitivity reactions including rash, urticaria, and angioedema.
May cause sedation, depression, positive direct Coombs test, hemolytic anemia, hepatotoxicity, fluid/electrolyte imbalance, and sensitivity reactions; monitor liver function, CBC, and electrolytes.
Anuria,Hypersensitivity to hydrochlorothiazide, hydralazine, or sulfonamide-derived drugs,Severe renal impairment (Cr Cl <30 m L/min),Use with MAO inhibitors (monoamine oxidase inhibitors),Pregnancy (especially second and third trimester) due to hydralazine
Hypersensitivity to methyldopa, hydrochlorothiazide, or sulfonamides; active hepatic disease; anuria; history of methyldopa-induced liver disorders.
Avoid high-potassium foods (bananas, oranges, tomatoes, spinach, salt substitutes) unless directed. Take with food to reduce gastrointestinal upset. Grapefruit juice may increase drug levels; avoid consumption.
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: Hydralazine (component of HYDRA-ZIDE) not associated with major malformations; thiazide diuretics (hydrochlorothiazide) have equivocal risk, some studies suggest increased risk of congenital anomalies, but confounded by underlying disease. Second and third trimesters: Thiazides may cause fetal/neonatal electrolyte disturbances, thrombocytopenia, and jaundice; hydralazine may cause neonatal lupus-like syndrome, thrombocytopenia, and hypotension. Use only if clearly needed.
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 and hydrochlorothiazide are excreted into breast milk in low amounts. M/P ratio not established. Hydrochlorothiazide may suppress lactation and cause neonatal electrolyte disturbances. Caution advised; monitor infant for jaundice, electrolyte imbalance, and dehydration.
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.
Pregnancy-induced increased plasma volume and renal clearance may necessitate dose escalation. Start at lowest effective dose; titrate to blood pressure control. Hydrochlorothiazide is generally avoided as a first-line agent due to volume depletion risks. Hydralazine often used as add-on therapy; dose adjustments based on clinical response.
No standard dose adjustment required, but increased plasma volume in pregnancy may necessitate higher doses of methyldopa. Monitor clinical response and adjust accordingly.
Monitor serum potassium and creatinine before initiation and periodically; hypokalemia common early, but may cause hyperkalemia in renal impairment. Avoid use in pregnancy (category D). Titrate dose slowly to minimize orthostatic hypotension. Add-on therapy often requires lower doses of each component.
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 or stop without consulting your doctor.,This drug contains two medicines; your doctor may adjust other medications accordingly.,Stand up slowly to prevent dizziness or fainting.,Report symptoms of electrolyte imbalance: muscle cramps, weakness, irregular heartbeat, or excessive thirst.,Avoid alcohol and NSAIDs (ibuprofen, naproxen) unless approved by your doctor.
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 HYDRA-ZIDE vs ALDORIL 25, answered by our medical review team.
HYDRA-ZIDE is a Antihypertensive Combination that works by Hydra-Zide is a combination of hydrochlorothiazide (thiazide diuretic) and hydralazine (direct vasodilator). Hydrochlorothiazide inhibits the sodium-chloride symporter in the distal convoluted tubule, reducing electrolyte reabsorption and increasing urine output. Hydralazine relaxes arteriolar smooth muscle, decreasing systemic vascular resistance and afterload.. 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 HYDRA-ZIDE and ALDORIL 25 depend on the specific clinical indication. These are both Antihypertensive Combination agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of HYDRA-ZIDE is: Oral, 1 tablet (25 mg hydrochlorothiazide / 50 mg hydralazine) twice daily, titrated up to maximum of 2 tablets twice daily based on blood pressure response.. 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 HYDRA-ZIDE 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. HYDRA-ZIDE is classified as Category C. First trimester: Hydralazine (component of HYDRA-ZIDE) not associated with major malformations; thiazide diuretics (hydrochlorothiazide) have equivocal risk, some studies suggest i. 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.