AZILSARTAN MEDOXOMIL AND CHLORTHALIDONE
Clinical safety rating: caution
Other antihypertensive drugs can have additive effects Lithium levels may be increased Can cause hypokalemia and hyponatremia.
Azilsartan medoxomil is an angiotensin II receptor antagonist that selectively blocks the binding of angiotensin II to AT1 receptors, reducing vasoconstriction and aldosterone secretion. Chlorthalidone is a thiazide-like diuretic that inhibits sodium reabsorption in the distal convoluted tubule, increasing sodium and water excretion.
| Metabolism | Azilsartan medoxomil is metabolized via hydrolysis to azilsartan, which is further metabolized by CYP2C9 and glucuronidation (UGT1A1, UGT1A3, UGT2B7). Chlorthalidone is primarily excreted unchanged in urine, with minor hepatic metabolism. |
| Excretion | Azilsartan medoxomil: Approximately 55% of the dose is excreted in feces and 42% in urine, mostly as metabolites. Chlorthalidone: Primarily excreted unchanged in urine (50-70%) via tubular secretion; approximately 30% is excreted in feces via biliary elimination. |
| Half-life | Azilsartan medoxomil: Terminal half-life approximately 11 hours. Chlorthalidone: Long terminal half-life of 40-60 hours (mean 47 hours), allowing once-daily dosing. |
| Protein binding | Azilsartan medoxomil: >99% bound to serum albumin. Chlorthalidone: 75% bound to albumin and erythrocytes. |
| Volume of Distribution | Azilsartan medoxomil: Vd of 16 L (approximately 0.2 L/kg). Chlorthalidone: Vd of approximately 3-4 L/kg, indicating extensive tissue binding. |
| Bioavailability | Azilsartan medoxomil: Oral bioavailability approximately 60% (after conversion to azilsartan). Chlorthalidone: Oral bioavailability approximately 65% (varies from 60-70% with formulation). |
| Onset of Action | Azilsartan medoxomil: Peak plasma concentration at 1.5-3 hours; antihypertensive effect begins within 2 weeks. Chlorthalidone: Diuresis begins within 2 hours, maximal effect at 2-6 hours; antihypertensive effect may take 2-4 weeks. |
| Duration of Action | Azilsartan medoxomil: Antihypertensive effect persists for 24 hours with once-daily dosing. Chlorthalidone: Diuretic effect lasts 24-72 hours; antihypertensive effect persists for 24 hours. |
| Molecular Weight | Azilsartan medoxomil: 568.6 Da; Chlorthalidone: 338.8 Da |
Azilsartan medoxomil 40 mg/chlorthalidone 12.5 mg or 25 mg orally once daily; maximum dose: azilsartan medoxomil 40 mg/chlorthalidone 25 mg per day.
| Dosage form | TABLET |
| Renal impairment | Contraindicated if GFR <30 mL/min/1.73 m². For GFR 30-60 mL/min/1.73 m², initiate with lowest available dose (e.g., azilsartan 40 mg/chlorthalidone 12.5 mg) and monitor renal function. No adjustment for GFR >60 mL/min/1.73 m². |
| Liver impairment | Contraindicated in Child-Pugh Class C (severe hepatic impairment). For Child-Pugh Class A or B, use with caution; no specific dose adjustment recommended, but monitor blood pressure and renal function. |
| Pediatric use | Safety and effectiveness in pediatric patients (<18 years) have not been established. Not recommended. |
| Geriatric use | Initiate therapy at the lowest dose (azilsartan medoxomil 40 mg/chlorthalidone 12.5 mg once daily) and titrate slowly due to increased risk of hypotension, electrolyte disturbances, and renal impairment. Monitor closely. |
| 1st trimester | Avoid. Based on animal data, potential for fetal renal effects; limited human data. Use alternative antihypertensive if possible. |
| 2nd trimester | Contraindicated. Drugs acting on the renin-angiotensin system (AZILSARTAN) can cause oligohydramnios, fetal renal dysfunction, and skull hypoplasia. CHLORTHALIDONE may cause electrolyte imbalances. |
| 3rd trimester | Contraindicated. Same risks as T2, with addition of neonatal hypotension, hyperkalemia, and renal failure. |
Clinical note
Other antihypertensive drugs can have additive effects Lithium levels may be increased Can cause hypokalemia and hyponatremia.
| FDA category | Animal |
| Placental transfer | Both components cross the placenta. Azilsartan: likely crosses, similar to other ARBs. Chlorthalidone: crosses placenta with evidence of fetal effects. |
■ FDA Black Box Warning
Fetal toxicity: Drugs acting directly on the renin-angiotensin system (RAS) can cause injury and death to the developing fetus when used during pregnancy. Discontinue as soon as possible once pregnancy is detected.
| Common Effects | edema |
| Serious Effects |
PregnancyHistory of hypersensitivity to azilsartan or chlorthalidoneAnuriaConcurrent use with aliskiren in patients with diabetes
| Precautions | Avoid use in pregnancy, Hypotension in volume- or salt-depleted patients, Monitor renal function, Electrolyte imbalances (hypokalemia, hyponatremia), Acute angle-closure glaucoma (sulfonamide component), Exacerbation of SLE, Impaired renal function |
| Food/Dietary | Avoid high-potassium foods (bananas, oranges, potatoes, spinach, avocados) and potassium-containing salt substitutes due to additive hyperkalemia risk. Alcohol may potentiate orthostatic hypotension. |
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| Breastfeeding |
| Azilsartan is excreted in animal milk; unknown in human milk. Chlorthalidone is excreted in breast milk and may suppress lactation. Use is not recommended due to potential adverse effects on infant electrolyte balance and renal function. |
| Lactation Rating | L5 - Contraindicated |
| Teratogenic Risk | Azilsartan medoxomil, an angiotensin II receptor blocker (ARB), and chlorthalidone, a thiazide diuretic, are both associated with fetal risks. First trimester: Potential for teratogenicity is low but not excluded; ARBs have a risk of renal anomalies. Second and third trimesters: ARBs cause oligohydramnios, fetal renal dysfunction, skull ossification defects, and hypotension; chlorthalidone may cause fetal electrolyte disturbances, jaundice, and thrombocytopenia. Both drugs should be avoided in pregnancy, especially second and third trimesters. |
| Fetal Monitoring | Monitor maternal blood pressure, renal function, electrolytes, and urine output. If inadvertent exposure during second/third trimester, perform fetal ultrasound for amniotic fluid volume and renal function, and neonatal monitoring for hypotension and hyperkalemia. |
| Fertility Effects | Azilsartan: No specific human fertility data; animal studies show no adverse effects. Chlorthalidone: May cause reversible impotence in men; no known effect on female fertility. Overall, no significant impact on fertility documented. |
| Clinical Pearls | Monitor serum potassium and renal function within 1-2 weeks after initiation or dose adjustment due to dual RAAS blockade and diuretic effects. Avoid use in patients with GFR <30 mL/min/1.73 m². Abrupt discontinuation may cause rebound hypertension. Concomitant use with NSAIDs may reduce antihypertensive effect and increase nephrotoxicity risk. |
| Patient Advice | Take once daily with or without food, preferably in the morning to avoid nocturia. · Avoid salt substitutes containing potassium chloride due to risk of hyperkalemia. · Report symptoms of low blood pressure (dizziness, fainting) or electrolyte imbalance (muscle cramps, irregular heartbeat). · Maintain adequate fluid intake; avoid dehydration from excessive sweating, diarrhea, or vomiting. · Do not stop taking abruptly; consult your doctor before discontinuing. |