Half-Life of Atenolol
The elimination half-life of oral atenolol is approximately 6 to 7 hours in patients with normal renal function, but can increase significantly to up to 73 hours in patients with end-stage renal disease. 1
Pharmacokinetic Properties
Atenolol is a beta-1 selective (cardioselective) beta-adrenergic receptor blocking agent with several key pharmacokinetic characteristics:
- Absorption: Rapid but incomplete absorption from the gastrointestinal tract (approximately 50% of an oral dose is absorbed) 1
- Peak plasma levels: Reached between 2-4 hours after oral administration 1
- Protein binding: Very low, with only about 3-6% bound to plasma proteins 1, 2
- Metabolism: Unlike many other beta-blockers, atenolol undergoes minimal hepatic metabolism (only about 5%) 1, 2
- Elimination: Primarily excreted unchanged by the kidneys (over 85% of an intravenous dose is excreted in urine within 24 hours) 1
Factors Affecting Half-Life
The half-life of atenolol is significantly affected by renal function:
- Normal renal function: 6-9 hours 1, 2
- Moderate renal impairment: Progressively increases as GFR decreases 2
- Severe renal impairment: Can reach 36 hours in uremic patients with GFR <10 ml/min 2
- End-stage renal disease: Up to 73 hours without dialysis 3
- During hemodialysis: Reduced to approximately 7.5 hours 3
Clinical Implications
The renal-dependent elimination of atenolol has important clinical implications:
- Dosage adjustment: Required in patients with renal impairment 2
- Dialyzability: Atenolol is classified as "dialyzable" 4, with dialysis clearance reported at approximately 42.6 ml/min 3
- Post-dialysis rebound: Plasma atenolol levels may rise for a few hours after the end of dialysis 3
Comparison to Other Beta-Blockers
Atenolol differs from many other beta-blockers in its pharmacokinetic profile:
- Propranolol and metoprolol: Undergo extensive hepatic metabolism, unlike atenolol 1
- Nadolol: Similar to atenolol in having minimal hepatic metabolism 1
- Lipophilicity: Atenolol has low lipid solubility, resulting in less CNS penetration and fewer central nervous system effects compared to lipophilic beta-blockers like propranolol 5
The long half-life of atenolol in patients with normal renal function allows for once-daily dosing, providing 24-hour blood pressure control 1. However, in patients with renal impairment, the significantly prolonged half-life necessitates careful dosage adjustment to avoid drug accumulation and toxicity.