TENORMIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TENORMIN (TENORMIN).
Selective beta-1 adrenergic receptor antagonist; blocks catecholamine effects at beta-1 receptors, reducing heart rate, myocardial contractility, and blood pressure.
| Metabolism | Hepatic metabolism via glucuronidation; minimal CYP450 involvement; renal excretion of unchanged drug and metabolites. |
| Excretion | Renal elimination of unchanged drug (40-50%) and hepatic metabolism to inactive metabolites excreted in urine; <5% fecal. |
| Half-life | 6-7 hours (terminal); prolonged to 16-27 hours in renal impairment (CrCl <35 mL/min). |
| Protein binding | ~10% (weak; primarily albumin). |
| Volume of Distribution | 1.1 L/kg; distributes into extravascular tissues (e.g., lungs, heart). |
| Bioavailability | ~50% (oral; first-pass hepatic metabolism; interindividual variability). |
| Onset of Action | Oral: 1-2 hours (beta-blockade); IV: 5 minutes (rapid). |
| Duration of Action | 24 hours (once-daily dosing due to beta-blockade duration); clinical effect persists >24 h in some patients. |
Hypertension: 50 mg orally once daily; may increase to 100 mg once daily. Angina: 50 mg orally once daily; may increase to 100 mg once daily. Acute MI: 5 mg IV over 5 minutes, followed by 50 mg orally 15 minutes later, then 50 mg orally 12 hours later, then 100 mg orally once daily.
| Dosage form | TABLET |
| Renal impairment | CrCl 15-35 mL/min: max dose 50 mg/day. CrCl <15 mL/min: max dose 25 mg/day or 50 mg every other day. Hemodialysis: 25-50 mg after dialysis. |
| Liver impairment | No dosage adjustment necessary for hepatic impairment. |
| Pediatric use | Not FDA-approved for pediatric use; limited data: 1-2 mg/kg/day orally divided twice daily, titrate to effect. |
| Geriatric use | Start at 25 mg orally once daily; titrate slowly due to increased sensitivity and reduced renal function. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for TENORMIN (TENORMIN).
| Breastfeeding | Atenolol (TENORMIN) is excreted into breast milk; M/P ratio ~1.5-6.8. Relative infant dose ~5-12% of maternal weight-adjusted dose. Caution: monitor infant for bradycardia and hypotension. Consider benefit vs risk; alternative agents with lower milk levels may be preferred. |
| Teratogenic Risk | First trimester: limited human data; animal studies show no major teratogenicity. Second/third trimesters: associated with fetal bradycardia, growth restriction, placental insufficiency; avoid if possible. Late pregnancy: risk of neonatal bradycardia, hypoglycemia, hypotension. |
■ FDA Black Box Warning
No FDA black box warning.
| Common Effects | Fatigue Slow heart rate Cold extremities Gastrointestinal disturbance |
| Serious Effects |
["Sinus bradycardia","Heart block greater than first degree","Cardiogenic shock","Decompensated heart failure","Hypersensitivity to atenolol or any component"]
| Precautions | ["Abrupt withdrawal may exacerbate angina or precipitate myocardial infarction","Exacerbation of heart failure","Bradycardia and heart block","May mask signs of hyperthyroidism","May worsen peripheral vascular disease","Anaphylactic reactions may be more severe","Use caution in patients with bronchospastic disease"] |
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| Fetal Monitoring |
| Monitor maternal blood pressure, heart rate; assess for signs of heart failure. Fetal assessment: serial ultrasound for growth restriction, amniotic fluid index; fetal heart rate monitoring for bradycardia. Neonatal: monitor for bradycardia, hypoglycemia, respiratory depression for 48-72 hours after delivery. |
| Fertility Effects | Atenolol (TENORMIN) may cause erectile dysfunction and decreased libido; theoretical risk of reduced sperm motility. No established effect on female fertility. Use during pregnancy can affect fetal development. |