Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
HYDRA-ZIDE vs ALDOCLOR-250
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.
Aldoclor-250 is a combination of methyldopa and chlorothiazide. Methyldopa is a centrally acting alpha-2 adrenergic agonist that reduces sympathetic outflow from the brain, decreasing peripheral vascular resistance and blood pressure. Chlorothiazide is a thiazide diuretic that inhibits sodium and chloride reabsorption in the distal convoluted tubule, increasing urinary output and reducing plasma volume.
Treatment of hypertension
Hypertension (first-line or adjunctive therapy),Off-label: Management of hypertensive crisis (as part of combination therapy)
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.
250 mg orally twice daily
Hydralazine: 2-4 hours (fast acetylators), 4-8 hours (slow acetylators); thiazide: 6-15 hours.
1.5-3 hours; prolonged in renal impairment (up to 20 hours with Cr Cl <10 m L/min).
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: Primarily hepatic metabolism via catecholamine pathways; conjugated to sulfate and other metabolites. Chlorothiazide: Not extensively metabolized; excreted unchanged in urine.
Renal: 50-70% of hydralazine as metabolites, 30-40% as parent drug; thiazide: 95% renal as unchanged drug.
Renal (70-80% unchanged), biliary/fecal (15-25% as metabolites); total clearance ~250 m L/min.
Hydralazine: 85-90% bound to albumin; thiazide: 40-70% bound to albumin.
25-40% bound primarily to albumin and alpha-1-acid glycoprotein.
Hydralazine: 1.5-2.5 L/kg (distributes extensively into tissues); thiazide: 0.2-0.5 L/kg (primarily extracellular fluid).
0.6-1.0 L/kg; indicates distribution into total body water and some tissue binding.
Hydralazine: 30-50% (oral, variable due to first-pass metabolism); thiazide: 60-80% (oral).
70-90% (oral); 100% (IV).
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.
Cr Cl >50 m L/min: no adjustment; Cr Cl 10-50 m L/min: 250 mg once daily; Cr Cl <10 m L/min: 250 mg every 48 hours
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: use with caution, reduce dose by 50%; Child-Pugh C: avoid use
Not approved for pediatric use; safety and efficacy not established. Alternative antihypertensives preferred.
Not recommended for use in pediatric patients due to lack of safety and efficacy data
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 lower end of dosing range; monitor renal function closely; adjust dose based on Cr Cl
There is no FDA black box warning for Hydra-Zide.
None explicitly listed. However, methyldopa carries a warning for hepatotoxicity and hemolytic anemia; chlorothiazide carries a warning for electrolyte disturbances and hypersensitivity reactions.
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.
Hepatotoxicity (methyldopa), hemolytic anemia, positive direct Coombs test, sedation, depression, bradycardia, orthostatic hypotension, electrolyte imbalance (hypokalemia, hyponatremia, hypomagnesemia), hyperuricemia, hyperglycemia, photosensitivity, lupus-like syndrome, and hypersensitivity reactions.
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, history of previous methyldopa-induced liver dysfunction, hemolytic anemia associated with methyldopa, anuria, hypersensitivity to methyldopa, chlorothiazide, or sulfonamide-derived drugs, severe renal impairment (Cr Cl <30 m L/min), and concomitant therapy with MAO inhibitors.
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-potassium foods (bananas, oranges, spinach) unless specifically advised; chlorothiazide may cause potassium loss, but methyldopa can cause potassium retention. Avoid excessive alcohol intake as it may potentiate hypotension. Take with food to reduce gastrointestinal upset. May decrease glucose tolerance; monitor in diabetic patients.
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.
FDA Pregnancy Category D. First trimester: Associated with cardiovascular defects (e.g., VSD), neural tube defects, and oral clefts. Second and third trimesters: Fetal nephrotoxicity (oligohydramnios, renal failure), premature closure of ductus arteriosus, pulmonary hypertension, and intracranial hemorrhage. Avoid in third trimester.
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.
Chlorothiazide is excreted in breast milk; M/P ratio unknown. Can suppress lactation. Use only if maternal benefit outweighs potential infant risks (e.g., electrolyte disturbances, thrombocytopenia).
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.
Increased volume of distribution and GFR in pregnancy may necessitate higher doses for equivalent effect. Start at lowest effective dose; titrate based on BP response. Monitor for hypokalemia and metabolic alkalosis.
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.
Aldoclor-250 is a combination of methyldopa (250mg) and chlorothiazide. Methyldopa can cause a positive direct Coombs test (10-20% of patients) which may interfere with blood cross-matching; obtain a hematocrit and Coombs test before therapy and at 6 and 12 months. Chlorothiazide may cause hypokalemia; monitor potassium and consider potassium supplementation. Onset of methyldopa is 3-6 hours; delay full effect for 48-72 hours. Avoid use in patients with active liver disease or history of previous methyldopa-induced liver dysfunction.
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 exactly as prescribed; do not skip doses or stop suddenly.,May cause drowsiness or dizziness; avoid driving or operating machinery until you know how it affects you.,Rise slowly from sitting or lying to prevent lightheadedness.,Report any unexplained fever, jaundice, or dark urine immediately.,Use sun protection; this drug may increase sensitivity to sunlight.,Do not use potassium supplements or salt substitutes without consulting your doctor.,If you miss a dose, take it as soon as you remember unless it's near the next dose; do not double.
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 ALDOCLOR-250, 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.. ALDOCLOR-250 is a Antihypertensive Combination (Central Alpha Agonist and Thiazide Diuretic) that works by Aldoclor-250 is a combination of methyldopa and chlorothiazide. Methyldopa is a centrally acting alpha-2 adrenergic agonist that reduces sympathetic outflow from the brain, decreasing peripheral vascular resistance and blood pressure. Chlorothiazide is a thiazide diuretic that inhibits sodium and chloride reabsorption in the distal convoluted tubule, increasing urinary output and reducing plasma volume.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between HYDRA-ZIDE and ALDOCLOR-250 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 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 ALDOCLOR-250 is: 250 mg orally 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 ALDOCLOR-250 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. ALDOCLOR-250 is classified as Category C. FDA Pregnancy Category D. First trimester: Associated with cardiovascular defects (e.g., VSD), neural tube defects, and oral clefts. Second and third trimesters: Fetal nephrotoxici. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.