Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
METATENSIN #2 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
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.
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.
Hypertension
Hypertension
1-2 tablets orally every 12 hours; each tablet contains reserpine 0.1 mg, hydralazine 25 mg, hydrochlorothiazide 15 mg.
1 tablet (hydrochlorothiazide 15 mg, methyldopa 250 mg) orally twice daily; increase as needed up to 2 tablets twice daily.
12 hours (terminal); clinical context: twice-daily dosing maintains stable plasma levels
Terminal half-life: 12–17 hours; clinical context: steady-state achieved within 2–3 days; effect persists 12–24 hours
Reserpine: primarily metabolized by CYP3A4; methyclothiazide: not extensively metabolized, excreted unchanged in urine.
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 (80% unchanged, 15% as glucuronide metabolite); biliary/fecal (5%)
Renal: ~70% unchanged; biliary/fecal: ~30% as metabolites
85% bound to albumin and alpha-1-acid glycoprotein
~90%, primarily to albumin
2.5 L/kg; indicates extensive tissue distribution
2–4 L/kg; clinical meaning: extensive tissue distribution, concentrating in vascular smooth muscle
Oral: 60% (first-pass metabolism reduces bioavailability)
Oral: 50–60% (extensive first-pass metabolism)
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.
GFR 30-50 m L/min: maximum 1 tablet twice daily. GFR <30 m L/min: avoid use.
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 A: caution, reduce dose. Child-Pugh B: avoid. Child-Pugh C: contraindicated.
Not recommended for children; safety and efficacy not established. Use alternative antihypertensives.
Not recommended for pediatric use; safety in children under 12 years not established.
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 once daily; monitor for hypotension and electrolyte imbalance. Reduce initial dose by 50%.
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, 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.
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 (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, 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 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: 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.
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.
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.
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.
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.
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.
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 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 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.
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 METATENSIN #2 vs ALDORIL 15, 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 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 METATENSIN #2 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 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 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 METATENSIN #2 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. 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 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.