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. |
| Molecular Weight | 266.34 |
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 | Associated with congenital abnormalities (e.g., heart defects) in retrospective studies; use only if clearly needed. |
| 2nd trimester | May cause fetal bradycardia and growth restriction; monitor fetal heart rate and growth. |
| 3rd trimester | Risk of neonatal bradycardia, hypotension, and hypoglycemia; discontinue 48-72 hours before delivery if possible. |
Clinical note
Comprehensive clinical and safety monograph for TENORMIN (TENORMIN).
| Placental transfer | Crosses placenta readily; cord blood levels approximate maternal levels. |
| Breastfeeding | Atenolol is excreted into breast milk in moderate amounts (relative infant dose ~5-15%). Monitor infant for bradycardia and hypotension; cautious use preferred. |
| Lactation Rating |
■ FDA Black Box Warning
No FDA black box warning.
| Common Effects | Fatigue Slow heart rate Cold extremities Gastrointestinal disturbance |
| Serious Effects |
Sinus bradycardiaHeart block greater than first degreeCardiogenic shockDecompensated heart failureSevere peripheral arterial diseaseBronchial asthma
| 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 |
| Food/Dietary | No significant food interactions. Avoid excessive alcohol intake as it may enhance hypotensive effect. Grapefruit juice does not interact significantly due to low hepatic metabolism. Maintain consistent dietary sodium intake as changes may alter antihypertensive response. |
Loading safety data…
| L3 (Moderately Safe) |
| 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. |
| 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. |
| Clinical Pearls | TENORMIN (atenolol) is a cardioselective beta-1 blocker with low lipid solubility, reducing CNS side effects. It is primarily renally excreted; dose adjustment required for CrCl <35 mL/min. Abrupt cessation can precipitate angina exacerbation or MI. Use with caution in asthma/COPD as it may increase airway resistance, though less than non-selective agents. May mask hypoglycemia symptoms (tachycardia) in diabetics. Efficacy in hypertension may take 1-2 weeks; maximum effect may not be seen for several weeks. |
| Patient Advice | Take exactly as prescribed; do not skip doses or stop suddenly without consulting your doctor. · Monitor blood pressure and pulse regularly; report if pulse <50 bpm or symptoms of bradycardia occur. · Avoid abrupt discontinuation; taper over 1-2 weeks to prevent rebound hypertension or chest pain. · May cause drowsiness or dizziness; avoid driving or operating heavy machinery until you know how it affects you. · Inform all healthcare providers you are taking this medication before surgery or dental procedures. · Report signs of heart failure (shortness of breath, swelling in ankles/feet) or worsening chest pain. · May mask signs of low blood sugar (e.g., rapid heartbeat); diabetic patients should monitor glucose closely. |