Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
HYDRA-ZIDE 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
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.
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.
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.
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); thiazide: 6-15 hours.
Terminal half-life: 12–17 hours; clinical context: steady-state achieved within 2–3 days; effect persists 12–24 hours
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 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.
Renal: 50-70% of hydralazine as metabolites, 30-40% as parent drug; thiazide: 95% renal as unchanged drug.
Renal: ~70% unchanged; biliary/fecal: ~30% as metabolites
Hydralazine: 85-90% bound to albumin; thiazide: 40-70% bound to albumin.
~90%, primarily to albumin
Hydralazine: 1.5-2.5 L/kg (distributes extensively into tissues); thiazide: 0.2-0.5 L/kg (primarily extracellular fluid).
2–4 L/kg; clinical meaning: extensive tissue distribution, concentrating in vascular smooth muscle
Hydralazine: 30-50% (oral, variable due to first-pass metabolism); thiazide: 60-80% (oral).
Oral: 50–60% (extensive first-pass metabolism)
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: maximum 1 tablet twice daily. GFR <30 m L/min: avoid use.
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: caution, reduce dose. Child-Pugh B: avoid. Child-Pugh C: contraindicated.
Not approved for pediatric use; safety and efficacy not established. Alternative antihypertensives preferred.
Not recommended for pediatric use; safety in children under 12 years not established.
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 with 1 tablet once daily; monitor for hypotension and electrolyte imbalance. Reduce initial dose by 50%.
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.
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.
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
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 (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 as they can reduce antihypertensive efficacy. Thiazides may cause hypokalemia; increase dietary potassium (bananas, orange juice) unless contraindicated. Alcohol may enhance orthostatic hypotension.
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: 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 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 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.
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.
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.
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 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 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.
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 HYDRA-ZIDE vs ALDORIL 15, 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 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 HYDRA-ZIDE and ALDORIL 15 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 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 HYDRA-ZIDE 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. 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 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.