Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
ARALEN HYDROCHLORIDE 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
Chloroquine, a 4-aminoquinoline, accumulates in acidic organelles such as lysosomes and food vacuoles of malaria parasites, raising p H and inhibiting hemozoin polymerization, which leads to toxic heme accumulation and parasite death. It also has anti-inflammatory and immunomodulatory effects by inhibiting TLR signaling and cytokine production.
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 uncomplicated malaria due to chloroquine-sensitive Plasmodium species,Prophylaxis of malaria in areas with chloroquine-sensitive parasites,Extraintestinal amebiasis,Treatment of discoid lupus erythematosus (off-label),Treatment of rheumatoid arthritis (off-label)
Hypertension
Chloroquine phosphate 500 mg (300 mg base) orally once weekly for prophylaxis; 600 mg base (1 g phosphate) orally initially, followed by 300 mg base (500 mg phosphate) at 6, 24, and 48 hours for treatment of malaria.
1 tablet (hydrochlorothiazide 15 mg, methyldopa 250 mg) orally twice daily; increase as needed up to 2 tablets twice daily.
48-72 hours (terminal elimination half-life); prolonged to weeks with chronic dosing due to extensive tissue accumulation, especially in the liver, spleen, and melanin-containing tissues.
Terminal half-life: 12–17 hours; clinical context: steady-state achieved within 2–3 days; effect persists 12–24 hours
Hepatic metabolism via CYP2C8, CYP3A4, and CYP2D6 to desethylchloroquine and other metabolites.
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 (~70% unchanged), with 10-20% in feces; biliary elimination is minor.
Renal: ~70% unchanged; biliary/fecal: ~30% as metabolites
50-60%, primarily to albumin and α1-acid glycoprotein.
~90%, primarily to albumin
50-100 L/kg; extensive tissue sequestration including erythrocytes, liver, spleen, and melanin-containing tissues like skin and retina.
2–4 L/kg; clinical meaning: extensive tissue distribution, concentrating in vascular smooth muscle
Oral: ~70-80% (variable due to first-pass metabolism); intravenous: 100%.
Oral: 50–60% (extensive first-pass metabolism)
Severe renal impairment (GFR <10 m L/min): reduce dose by 50% or increase dosing interval.
GFR 30-50 m L/min: maximum 1 tablet twice daily. GFR <30 m L/min: avoid use.
Use with caution in patients with hepatic impairment; no specific dose adjustment guidelines available; contraindicated in severe hepatic disease or porphyria.
Child-Pugh A: caution, reduce dose. Child-Pugh B: avoid. Child-Pugh C: contraindicated.
Prophylaxis: 5 mg base/kg orally once weekly (max 300 mg base). Treatment: 10 mg base/kg orally initially, then 5 mg base/kg at 6, 24, and 48 hours (max 600 mg base total).
Not recommended for pediatric use; safety in children under 12 years not established.
Start at lower end of dosing range due to increased risk of adverse effects (e.g., QT prolongation, retinal toxicity); monitor renal function.
Start with 1 tablet once daily; monitor for hypotension and electrolyte imbalance. Reduce initial dose by 50%.
No FDA black box warning.
None
Retinopathy and irreversible retinal damage with prolonged use or high doses; requires baseline and periodic ophthalmologic exams,QT prolongation and ventricular arrhythmias, especially with concomitant QT-prolonging drugs or electrolyte abnormalities,Severe hypoglycemia including loss of consciousness,Neuropsychiatric effects including psychosis and suicidal ideation,Hemolysis in glucose-6-phosphate dehydrogenase (G6PD) deficiency
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.
Hypersensitivity to chloroquine or any 4-aminoquinoline,Pre-existing retinopathy or known maculopathy,Known G6PD deficiency (relative, use with caution),Concomitant use with strong QT-prolonging drugs (e.g., quinidine, procainamide)
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 grapefruit and grapefruit juice as they may increase drug levels and toxicity. Limit alcohol intake to reduce risk of liver toxicity. Administer with food to decrease gastrointestinal irritation. Avoid antacids containing aluminum or magnesium; separate by at least 4 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.
Chloroquine hydrochloride crosses the placenta. First trimester: associated with increased risk of spontaneous abortion and congenital abnormalities (cochleovestibular and ocular) at high doses. Second and third trimesters: possible ototoxicity and retinal toxicity; use only for malaria prophylaxis or treatment when benefit outweighs risk.
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.
Chloroquine is excreted into breast milk in low concentrations (M/P ratio approximately 0.1-0.3). Amounts are unlikely to cause adverse effects in nursing infants. The American Academy of Pediatrics considers chloroquine compatible with breastfeeding. Monitor infant for potential ocular effects.
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 clearance during pregnancy may require higher doses for malaria prophylaxis (e.g., 400 mg base weekly) and treatment; therapeutic drug monitoring recommended for optimal dosing. No standard dose adjustment established; base dose on indication and 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.
ARALEN HYDROCHLORIDE (chloroquine hydrochloride) is used for malaria prophylaxis and treatment, and for amebiasis. Monitor for retinal toxicity with long-term use; baseline and periodic ophthalmologic exams recommended. Caution in patients with hepatic disease, G6PD deficiency, or porphyria. May exacerbate psoriasis and myasthenia gravis. QT prolongation possible; avoid with other QT-prolonging drugs. Administer with food to reduce GI upset. For acute malaria, dose may be divided to improve tolerance. In severe malaria, use parenteral form with cardiac monitoring.
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 this medication exactly as prescribed; do not skip doses for malaria prophylaxis.,If vomiting occurs within 1 hour of a dose, contact your healthcare provider for instructions.,Report any vision changes, such as blurred vision or difficulty focusing, immediately.,Avoid alcohol and limit caffeine intake as they may increase gastrointestinal side effects.,Use effective contraception during treatment if you are of childbearing potential.,Do not take antacids or kaolin within 4 hours of this medication.,Seek medical attention if you experience signs of allergic reaction: rash, hives, swelling, or difficulty breathing.
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 ARALEN HYDROCHLORIDE vs ALDORIL 15, answered by our medical review team.
ARALEN HYDROCHLORIDE is a Antimalarial that works by Chloroquine, a 4-aminoquinoline, accumulates in acidic organelles such as lysosomes and food vacuoles of malaria parasites, raising p H and inhibiting hemozoin polymerization, which leads to toxic heme accumulation and parasite death. It also has anti-inflammatory and immunomodulatory effects by inhibiting TLR signaling and cytokine production.. 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 ARALEN HYDROCHLORIDE and ALDORIL 15 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 ARALEN HYDROCHLORIDE is: Chloroquine phosphate 500 mg (300 mg base) orally once weekly for prophylaxis; 600 mg base (1 g phosphate) orally initially, followed by 300 mg base (500 mg phosphate) at 6, 24, and 48 hours for treatment of malaria.. 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 ARALEN HYDROCHLORIDE 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. ARALEN HYDROCHLORIDE is classified as Category C. Chloroquine hydrochloride crosses the placenta. First trimester: associated with increased risk of spontaneous abortion and congenital abnormalities (cochleovestibular and ocular) . 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.