TENORETIC 50
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TENORETIC 50 (TENORETIC 50).
Atenolol is a cardioselective beta-1 adrenergic receptor antagonist that reduces heart rate, myocardial contractility, and blood pressure. Chlorthalidone is a thiazide-like diuretic that inhibits sodium-chloride symporter in the distal convoluted tubule, increasing excretion of sodium and water, reducing plasma volume.
| Metabolism | Atenolol is primarily excreted unchanged by the kidneys, with minimal hepatic metabolism. Chlorthalidone is excreted unchanged in urine, with some metabolism in the liver via glucuronidation. |
| Excretion | Renal: atenolol 40-50% unchanged, chlorthalidone >95% unchanged; biliary/fecal minimal |
| Half-life | Atenolol: 6-7 hr (up to 20 hr in renal impairment); chlorthalidone: 40-60 hr (prolonged in renal impairment) |
| Protein binding | Atenolol: <5% bound to albumin; chlorthalidone: 75% bound to albumin and erythrocytes |
| Volume of Distribution | Atenolol: 0.7-1.2 L/kg (low, reflects hydrophilicity); chlorthalidone: 4.8 L/kg (extensive tissue distribution) |
| Bioavailability | Oral: atenolol ~50% (first-pass metabolism minimal); chlorthalidone ~65% |
| Onset of Action | Oral: 1-2 hr for atenolol, 2-3 hr for chlorthalidone diuretic effect |
| Duration of Action | Atenolol: 24 hr (once-daily dosing); chlorthalidone: 24-72 hr (effective for 24 hr with once-daily dosing) |
1 tablet (atenolol 50 mg / chlorthalidone 25 mg) orally once daily, may increase to 2 tablets once daily if needed.
| Dosage form | TABLET |
| Renal impairment | CrCl 35-50 mL/min: maximum atenolol 50 mg daily; CrCl 15-34 mL/min: maximum atenolol 25 mg daily; CrCl <15 mL/min: contraindicated. |
| Liver impairment | No specific adjustment for mild-to-moderate impairment. Severe impairment: use with caution, consider dose reduction. |
| Pediatric use | Not recommended for use in children; safety and efficacy not established. |
| Geriatric use | Start at lower dose (e.g., atenolol 25 mg / chlorthalidone 12.5 mg) and titrate carefully; monitor for hypotension and electrolyte imbalance. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for TENORETIC 50 (TENORETIC 50).
| Breastfeeding | Atenolol is excreted into breast milk with an M/P ratio of approximately 1.5-6.8; chlorthalidone M/P ratio is approximately 0.3-0.6. Monitor infant for bradycardia, hypotension, and hypoglycemia. Use with caution, especially in preterm or low-birth-weight infants. |
| Teratogenic Risk | First trimester: No adequate studies; risk cannot be ruled out. Second/third trimester: Atenolol (beta-blocker) may cause fetal bradycardia, intrauterine growth restriction, and placental hypoperfusion. Chlorthalidone (thiazide diuretic) may cause fetal electrolyte disturbances and neonatal hypoglycemia. Avoid use in pregnancy unless no alternative. |
■ FDA Black Box Warning
None
| Serious Effects |
Sinus bradycardia; heart block greater than first degree; cardiogenic shock; overt cardiac failure; hypersensitivity to any component; anuria; severe renal impairment (creatinine clearance <30 mL/min).
| Precautions | Exacerbation of angina and myocardial infarction upon abrupt withdrawal; bradycardia; heart failure; bronchospasm in asthmatic patients; hypotension; electrolyte disturbances (hypokalemia, hyponatremia, hypomagnesemia); hyperuricemia; diabetes mellitus (may mask hypoglycemia); renal impairment; peripheral vascular disease; thyrotoxicosis; anaphylactic reactions. |
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| Fetal Monitoring | Maternal: Blood pressure, heart rate, serum electrolytes (K+, Na+), renal function, uric acid, and glucose. Fetal: Ultrasound for growth restriction, fetal heart rate monitoring (bradycardia risk), and amniotic fluid assessment. |
| Fertility Effects | Beta-blockers may impair male fertility due to reduced sperm motility. No established effects on female fertility. Thiazide diuretics have no known significant impact on fertility. |