Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
METATENSIN #2 vs ALDORIL D50
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
METATENSIN #2 contains reserpine and methyclothiazide. Reserpine inhibits vesicular monoamine transporter (VMAT), depleting catecholamines from peripheral neurons. Methyclothiazide inhibits sodium-chloride symporter in distal convoluted tubule, reducing fluid volume.
Aldoril D50 is a combination of methyldopa and hydrochlorothiazide. 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 reabsorption in the distal convoluted tubule, reducing plasma volume and further lowering blood pressure.
Hypertension
Hypertension (first-line or second-line therapy),Hypertensive urgency (off-label)
1-2 tablets orally every 12 hours; each tablet contains reserpine 0.1 mg, hydralazine 25 mg, hydrochlorothiazide 15 mg.
1 tablet (hydrochlorothiazide 25 mg + methyldopa 250 mg) orally twice daily; maximum dose: 2 tablets (50 mg + 500 mg) twice daily.
12 hours (terminal); clinical context: twice-daily dosing maintains stable plasma levels
3–6 hours (terminal elimination half-life); clinical context: requires twice-daily dosing for sustained blood pressure control; prolonged in renal impairment.
Reserpine: primarily metabolized by CYP3A4; methyclothiazide: not extensively metabolized, excreted unchanged in urine.
Methyldopa is extensively metabolized in the liver via conjugation and O-methylation, with involvement of catechol-O-methyltransferase (COMT). Hydrochlorothiazide is not extensively metabolized; it is eliminated largely unchanged by the kidneys.
Renal (80% unchanged, 15% as glucuronide metabolite); biliary/fecal (5%)
Renal: 50% as unchanged drug and 20% as metabolites; biliary/fecal: ~25% (as metabolites); total renal clearance accounts for ~70% of elimination.
85% bound to albumin and alpha-1-acid glycoprotein
~20% bound to albumin; minimal binding to other plasma proteins.
2.5 L/kg; indicates extensive tissue distribution
0.2–0.3 L/kg (moderately low Vd, indicating limited extravascular distribution and predominantly plasma water distribution).
Oral: 60% (first-pass metabolism reduces bioavailability)
Oral: 30–40% (due to extensive first-pass metabolism); IV: 100%.
Contraindicated if Cr Cl <30 m L/min. For Cr Cl 30-60 m L/min, reduce dose by 50%; avoid if possible. Monitor potassium and creatinine.
Contraindicated if GFR < 30 m L/min; for GFR 30-50 m L/min: reduce dose and monitor electrolytes.
Contraindicated in severe hepatic impairment (Child-Pugh class C). For Child-Pugh class A or B, use with caution; reduce dose by 50% and monitor liver function.
Child-Pugh Class A: no adjustment; Class B: reduce dose by 50% and monitor; Class C: contraindicated.
Not recommended for children; safety and efficacy not established. Use alternative antihypertensives.
Not recommended; inadequate safety data.
Start at half the standard dose (0.5-1 tablet every 12 hours). Monitor for hypotension, electrolyte imbalance, and CNS effects (depression, sedation). Avoid in frail elderly.
Start with 1 tablet (hydrochlorothiazide 12.5 mg + methyldopa 125 mg) once daily; increase slowly; monitor for hypotension and electrolyte imbalance.
No FDA black box warning.
None
Mental depression,Electrolyte imbalance (hypokalemia, hyponatremia),Orthostatic hypotension,Increased gastric acid secretion,Pancreatitis,Exacerbation of systemic lupus erythematosus
Sedation and drowsiness common; avoid driving or hazardous activities. Risk of Coombs-positive hemolytic anemia with methyldopa (discontinue if anemia develops). Hepatotoxicity and liver function abnormalities (discontinue if jaundice occurs). Orthostatic hypotension; caution in volume-depleted patients. Electrolyte imbalances (particularly hypokalemia, hyponatremia) with hydrochlorothiazide; monitor serum electrolytes. Sulfonamide cross-sensitivity possible. Exacerbation of systemic lupus erythematosus. Avoid abrupt withdrawal of methyldopa (may cause rebound hypertension).
History of mental depression (especially with suicidal tendencies),Active peptic ulcer,Ulcerative colitis,Electroshock therapy,Hypersensitivity to reserpine, methyclothiazide, or sulfonamides,Anuria
Active hepatic disease (cirrhosis, hepatitis) associated with methyldopa therapy; previous methyldopa-induced liver disorders. Anuria or hypersensitivity to thiazide diuretics or sulfonamide-derived drugs. Concomitant use with MAO inhibitors. Severe renal impairment (creatinine clearance <30 m L/min) or electrolyte depletion due to hydrochlorothiazide. Concurrent lithium therapy (risk of lithium toxicity).
Avoid high-potassium foods (bananas, oranges, leafy greens) as hydrochlorothiazide can cause hypokalemia; monitor potassium levels. Use salt substitutes cautiously due to potassium content. Avoid excessive sodium intake which may counteract antihypertensive effects. Grapefruit juice may reduce methyldopa absorption; separate by 2 hours.
Avoid potassium supplements or salt substitutes containing potassium without consulting doctor. Limit alcohol intake. Avoid excessive grapefruit juice. Maintain adequate potassium intake through diet to prevent hypokalemia.
First trimester: Increased risk of cardiovascular and neural tube defects due to inhibition of folate-dependent enzymes. Second and third trimesters: Fetal bradycardia, oligohydramnios, intrauterine growth restriction, and neonatal hypotension. Avoid throughout pregnancy unless maternal benefit outweighs risks.
Hydrochlorothiazide (HCTZ) is Pregnancy Category B in first trimester and Category D in second/third trimesters. Methyldopa (M) is Category B. HCTZ use in second/third trimester may cause fetal/neonatal effects including electrolyte disturbances, jaundice, thrombocytopenia, and possible fetal growth restriction. Methyldopa has not shown teratogenicity. Aldoril D50 (M 500mg/HCTZ 50mg) is not recommended during pregnancy, especially after first trimester.
Excreted into breast milk; M/P ratio approximately 0.8. Potential for neonatal cardiovascular effects such as bradycardia and hypotension. Caution advised; monitor infant for signs of β-blockade.
Both methyldopa and HCTZ are excreted in breast milk. Methyldopa M/P ratio approximately 1.0; HCTZ M/P ratio variable, small amounts. Use during breastfeeding may suppress lactation due to HCTZ diuretic effect. Monitor infant for signs of hypotension, electrolyte imbalance. Caution recommended; use only if clearly needed.
Increased volume of distribution and renal clearance in pregnancy may necessitate dose escalation. Start at lowest effective dose, titrate based on blood pressure response. Monitor for hypotension and adjust accordingly.
Pregnancy-induced increase in plasma volume may reduce effectiveness of HCTZ, requiring dose adjustment. Methyldopa pharmacokinetics not significantly altered; however, increased clearance in pregnancy may require higher doses. In preeclampsia, dose adjustments may be needed. Avoid HCTZ in pregnancy if possible.
METATENSIN #2 is a fixed-dose combination of methyldopa and hydrochlorothiazide. Monitor for hypotension, especially during initial dosing. LFTs and CBC at baseline and periodically due to methyldopa's risk of hepatotoxicity and hemolytic anemia. Use with caution in renal impairment (Cr Cl <30 m L/min). Discontinue if jaundice occurs. Adjust dose in hepatic disease.
ALDORIL D50 combines methyldopa and hydrochlorothiazide. Monitor for orthostatic hypotension, especially in volume-depleted patients. May cause positive Coombs test, hemolytic anemia, and lupus-like syndrome. Avoid in pheochromocytoma. Use caution in hepatic disease.
Take exactly as prescribed at the same time each day.,May cause dizziness or drowsiness; avoid driving until effects are known.,Rise slowly from sitting or lying to prevent lightheadedness.,Report jaundice, fever, unexplained bruising/bleeding, or severe fatigue.,Use sun protection; hydrochlorothiazide increases photosensitivity.,Avoid alcohol, as it may worsen hypotension.,Do not stop abruptly; withdrawal can cause severe hypertension.
Take exactly as prescribed; do not skip doses or double up.,May cause dizziness or drowsiness; avoid driving until you know how it affects you.,Report unexplained fever, jaundice, or dark urine immediately.,Avoid sudden discontinuation; may cause rapid increase in blood pressure.,Stay hydrated but do not overhydrate; monitor for signs of electrolyte imbalance.
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 METATENSIN #2 vs ALDORIL D50, answered by our medical review team.
METATENSIN #2 is a Antihypertensive Combination that works by METATENSIN #2 contains reserpine and methyclothiazide. Reserpine inhibits vesicular monoamine transporter (VMAT), depleting catecholamines from peripheral neurons. Methyclothiazide inhibits sodium-chloride symporter in distal convoluted tubule, reducing fluid volume.. ALDORIL D50 is a Antihypertensive Combination that works by Aldoril D50 is a combination of methyldopa and hydrochlorothiazide. 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 reabsorption in the distal convoluted tubule, reducing plasma volume and further lowering blood pressure.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between METATENSIN #2 and ALDORIL D50 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 METATENSIN #2 is: 1-2 tablets orally every 12 hours; each tablet contains reserpine 0.1 mg, hydralazine 25 mg, hydrochlorothiazide 15 mg.. The standard adult dose of ALDORIL D50 is: 1 tablet (hydrochlorothiazide 25 mg + methyldopa 250 mg) orally twice daily; maximum dose: 2 tablets (50 mg + 500 mg) 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 METATENSIN #2 and ALDORIL D50 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. METATENSIN #2 is classified as Category C. First trimester: Increased risk of cardiovascular and neural tube defects due to inhibition of folate-dependent enzymes. Second and third trimesters: Fetal bradycardia, oligohydram. ALDORIL D50 is classified as Category C. Hydrochlorothiazide (HCTZ) is Pregnancy Category B in first trimester and Category D in second/third trimesters. Methyldopa (M) is Category B. HCTZ use in second/third trimester ma. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.