Atenolol vs Metoprolol for Beta-Blockade
Atenolol is preferred over metoprolol (Toprol) specifically in the perioperative setting, where it demonstrates superior outcomes with significantly lower rates of perioperative MI or death (2.5% vs 3.2%, p<0.001), but metoprolol is preferred in most other clinical contexts including heart failure, when IV administration may be needed, or when treating patients with reactive airway disease. 1, 2
Perioperative Setting: Atenolol Wins
The most robust evidence for choosing between these agents comes from the perioperative literature:
A large observational cohort study of 37,151 patients over age 65 undergoing elective surgery found atenolol was associated with significantly lower rates of perioperative MI or death compared to metoprolol (2.5% vs 3.2%, p<0.001). 1
This difference persisted after adjusting for demographic, clinical, and surgical factors, and the inclusion of other long-acting beta blockers yielded identical risk reduction to atenolol. 1
The ACC/AHA guidelines explicitly state that long-acting beta blockade (when therapy is initiated before surgery) may be superior to short-acting beta blockade, suggesting the mechanism relates to atenolol's longer half-life preventing acute withdrawal after missed perioperative doses. 1
If you are managing a patient requiring perioperative beta-blockade, choose atenolol. 2
Non-Perioperative Settings: Metoprolol Preferred
Outside the perioperative context, metoprolol has several practical advantages:
When IV Administration May Be Needed
Metoprolol has well-established IV dosing protocols (5 mg over 1-2 minutes, repeated every 5 minutes for maximum 15 mg total), making it the preferred choice in acute settings like unstable angina or NSTEMI. 2
Transition to oral metoprolol 25-50 mg every 6 hours can begin 15 minutes after the last IV dose. 2
For Patients with Reactive Airway Disease
The ACC specifically recommends metoprolol as the preferred short-acting beta-1 selective agent for patients with concerns about beta-blocker intolerance. 2
In patients with mild wheezing or COPD, a reduced dose of metoprolol (12.5 mg orally) is recommended rather than complete avoidance of beta-blockers. 2
Metoprolol's beta-1 selectivity provides more targeted cardiac effects with less bronchospasm risk compared to non-selective agents. 3
Heart Failure Context
For heart failure with reduced ejection fraction, carvedilol demonstrates 17% greater mortality reduction compared to metoprolol and is the preferred beta-blocker in this population. 3
However, both metoprolol succinate and carvedilol are acceptable for post-MI patients with LV dysfunction. 2, 3
Hypertension: Atenolol Questioned
Recent meta-analyses have questioned the cardiovascular benefit of atenolol in hypertension, showing no mortality benefit compared to placebo and higher stroke risk compared to other antihypertensives. 2, 4
The AHA recommends metoprolol over atenolol for hypertension treatment due to these questioned cardiovascular benefits of atenolol. 4
However, comparative trials between atenolol and metoprolol in hypertension have not been performed with regard to cardiovascular endpoints, so direct evidence is lacking. 5
Pharmacokinetic Differences
Atenolol's longer duration of action (half-life ~6-7 hours with renal elimination) allows reliable once-daily dosing. 2, 6
Standard metoprolol tartrate requires twice-daily administration due to its shorter half-life (~3-4 hours with hepatic metabolism). 2, 6
Studies show atenolol induces more effective BP reduction than metoprolol 25 hours after dosing, likely due to its longer plasma half-life. 6
Milligram for milligram, atenolol and metoprolol do not produce equivalent beta-blockade—metoprolol requires higher or more frequent dosing to achieve similar cardiovascular effects. 7
Practical Algorithm for Selection
Choose Metoprolol when:
- IV administration may be needed in acute settings 2
- Concerns exist about beta-blocker tolerance or reactive airway disease 2
- Patient has heart failure with reduced ejection fraction (though carvedilol is superior) 2, 3
- Treating hypertension without compelling perioperative indication 4
Choose Atenolol when:
- Perioperative beta-blockade is needed 1, 2
- Once-daily dosing is strongly preferred for adherence 2
- Long-acting beta-blockade is desired to prevent withdrawal effects 1
Critical Safety Considerations
Both agents should be avoided in patients with marked first-degree AV block, active asthma or severe reactive airway disease, decompensated heart failure, significant bradycardia or hypotension, and high-risk features for cardiogenic shock. 2
Never give the full 15 mg IV metoprolol as a rapid bolus—administer 5 mg increments over 1-2 minutes. 2
Never abruptly discontinue either agent, as this can cause severe exacerbation of angina, MI, and ventricular arrhythmias. 2
Perioperative beta-blocker discontinuation is associated with dramatically increased mortality (50% vs 1.5%, p<0.001) and cardiovascular mortality (29% vs 0%, p=0.005). 1