TENORETIC 100
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TENORETIC 100 (TENORETIC 100).
Tenoretic 100 is a combination of atenolol (a cardioselective beta-1 adrenergic receptor antagonist) and chlorthalidone (a thiazide-like diuretic that inhibits sodium reabsorption in the distal convoluted tubule). Atenolol reduces heart rate, cardiac output, and blood pressure by blocking beta-1 receptors; chlorthalidone reduces plasma volume and peripheral resistance.
| Metabolism | Atenolol: Minimal hepatic metabolism; primarily excreted unchanged by kidneys. Chlorthalidone: Not metabolized; excreted unchanged in urine. |
| Excretion | Tenoretic 100 (atenolol 100 mg + chlorthalidone 25 mg): Atenolol: ~85% renal unchanged, <10% fecal; Chlorthalidone: ~65% renal unchanged, remainder biliary/fecal. |
| Half-life | Atenolol: terminal half-life 6-7 h (up to 14 h in severe renal impairment); Chlorthalidone: 40-60 h (long-acting diuretic). |
| Protein binding | Atenolol: <5% bound to albumin; Chlorthalidone: ~75% bound to albumin and erythrocytes. |
| Volume of Distribution | Atenolol: 0.7-1.2 L/kg (moderate tissue distribution); Chlorthalidone: 3-4 L/kg (extensive tissue binding). |
| Bioavailability | Oral: Atenolol ~50% (first-pass); Chlorthalidone ~65%. |
| Onset of Action | Oral: atenolol antihypertensive effect 1-2 h; chlorthalidone diuresis 2 h, peak 4-6 h. |
| Duration of Action | Atenolol: 24 h (once-daily dosing); Chlorthalidone: 24-72 h (long duration permits QD/BID dosing). |
| Molecular Weight | 266.34 (atenolol base); 336.79 (chlorthalidone). |
One tablet orally once daily, each tablet containing atenolol 100 mg and chlorthalidone 25 mg. May be increased to 2 tablets once daily if needed.
| Dosage form | TABLET |
| Renal impairment | For CrCl 30-59 mL/min: maximum atenolol 50 mg/day; for CrCl <30 mL/min: maximum atenolol 25 mg/day. Chlorthalidone is ineffective if CrCl <30 mL/min. No adjustment for CrCl >60 mL/min. |
| Liver impairment | No specific Child-Pugh based adjustments are established; use with caution in severe hepatic impairment due to potential for electrolyte imbalance and altered drug metabolism. |
| Pediatric use | Not recommended for pediatric use; safety and efficacy not established. If used, atenolol dose: 0.5-1 mg/kg/day orally; chlorthalidone: 0.5-1 mg/kg/day orally. Adjust based on response and renal function. |
| Geriatric use | Start at lowest possible dose (e.g., atenolol 25-50 mg once daily) and titrate slowly due to increased risk of bradycardia, hypotension, and electrolyte disturbances. Monitor renal function closely. |
| 1st trimester | Contraindicated: associated with fetal renal abnormalities, oligohydramnios, and skull ossification defects. |
| 2nd trimester | Contraindicated: risk of fetal hypotension, renal failure, and oligohydramnios. |
| 3rd trimester | Contraindicated: may cause neonatal hypotension, hyperkalemia, and renal dysfunction. |
Clinical note
Comprehensive clinical and safety monograph for TENORETIC 100 (TENORETIC 100).
| Placental transfer | Atenolol extensively crosses placenta (fetal levels similar to maternal); chlorthalidone crosses placenta and appears in cord blood. |
| Breastfeeding | Atenolol (component) concentrates in breast milk with infant doses up to 6-7% of maternal weight-adjusted dose; monitor infant for bradycardia and hypotension. Chlorthalidone use during breastfeeding may suppress lactation; monitor infant for electrolyte imbalance. |
■ FDA Black Box Warning
Warning: Avoid abrupt discontinuation in patients with coronary artery disease; may exacerbate angina or precipitate myocardial infarction.
| Serious Effects |
BradycardiaHeart block greater than first degreeCardiogenic shockDecompensated heart failureSick sinus syndrome (without pacemaker)Severe peripheral arterial diseaseHypersensitivity to atenolol or chlorthalidoneAnuriaUncorrected electrolyte imbalance
| Precautions | Bradycardia or heart block, Exacerbation of peripheral arterial disease, Mask symptoms of hyperthyroidism, Electrolyte imbalances (hypokalemia, hyponatremia) due to chlorthalidone, Acute myopia and secondary angle-closure glaucoma, Renal impairment, Worsening of renal function, Hypotension or syncope |
| Food/Dietary | Avoid excessive potassium intake (bananas, oranges, spinach, salt substitutes). Limit alcohol. Grapefruit juice may enhance antihypertensive effect. Maintain adequate fluid intake. Avoid high-sodium foods to prevent blunting of antihypertensive effect. |
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| Lactation Rating | L4 (Possibly Hazardous) |
| Teratogenic Risk | First trimester: Risk of congenital malformations not established; animal studies show some fetal toxicity at high doses. Second and third trimesters: Associated with fetal growth restriction, oligohydramnios, neonatal bradycardia, and hypotension due to maternal beta-blockade and ACE inhibition (atenolol component). ACE inhibitor (chlorthalidone component not teratogenic but causes fetal nephrotoxicity and oligohydramnios). Avoid in pregnancy. |
| Fetal Monitoring | Monitor maternal blood pressure, heart rate, renal function, and electrolytes (potassium). In fetus: serial growth scans, amniotic fluid index (oligohydramnios risk), and fetal heart rate monitoring for bradycardia. Neonatal monitoring for hypotension, bradycardia, and hypoglycemia after delivery. |
| Fertility Effects | Beta-blockers (atenolol) may reduce libido and cause erectile dysfunction in males; no proven direct effect on female fertility. Thiazide diuretics may affect electrolyte balance and ovulation; data limited. Not associated with permanent infertility. |
| Clinical Pearls | Combination of atenolol (cardioselective beta-blocker) and chlorthalidone (thiazide-like diuretic). Monitor for bradycardia, hypotension, electrolyte imbalances, especially hypokalemia and hyponatremia. Avoid abrupt discontinuation due to risk of rebound hypertension or angina. Use with caution in asthma, COPD, diabetes, or peripheral vascular disease. Can mask hypoglycemia symptoms and hyperthyroidism. |
| Patient Advice | Take exactly as prescribed, usually once daily in the morning. · Do not stop taking suddenly without consulting your doctor. · Avoid alcohol and over-the-counter NSAIDs like ibuprofen. · Report slow heartbeat, dizziness, fainting, or swelling. · May cause drowsiness; avoid driving until you know how it affects you. · Stay hydrated but do not use salt substitutes high in potassium. · Monitor blood pressure regularly and keep appointments. · Inform healthcare providers you are taking this drug. |