Sunday, February 3, 2013

An appeal to avoid atenolol altogether

I was compelled to write the following entry after encountering my third patient in as many weeks who presented to the cardiology service with symptomatic bradycardia -- one of whom required admission to the cardiac intensive care unit for transvenous pacing -- all secondary to the accumulation of atenolol in the setting of new-onset renal impairment.  While we were able to avoid the placement of a permanent pacemaker in two of these patients, the third had underlying conduction abnormalities that were revealed by the beta blocker overdose

I suspect this is an all too common experience among clinicians in the area of cardiology practice, so I hope to make a case here for why atenolol should just be avoided altogether.

Of the beta blockers, atenolol is the most dependent on renal clearance -- nearly 50% is eliminated by the kidneys, making it problematic in patients with even mild to moderate renal impairment, not to mention in older patients, where renal function is less predictable and only deteriorates with time. There are some theoretical advantages to the use of atenolol, which probably explains why it remains so prevalent, but these characteristics rarely translate into clinically meaningful differences in everyday practice.  The purported duration of beta blockade with atenolol is 24 hours, but its impact on heart rate and blood pressure rarely last the full day in a majority of patients, often requiring that it be dosed twice daily (thus eliminating one of its only advantages over other beta blockers). Some clinicians feel atenolol has greater anti-hypertensive effects compared to other beta blockers, but given the poor impact of the class overall, this advantage is likely marginal at best. Besides, for patients who require beta blocker therapy for a compelling indication (e.g., after a myocardial infarction) and anti-hypertensive control, the addition of an another agent should be considered, as many of them demonstrate benefits independent of their anti-hypertensive effects (e.g., ACE inhibitors).

Otherwise, the evidence to support atenolol in patients who have had a myocardial infarction is no better than other beta blockers [1,2], and many of these alternatives are better supported in common comorbid conditions (e.g., metoprolol in patients with heart failure) [3]. Although the twice daily dosing strategy is often considered a theoretical disadvantage of many beta blockers, evidence suggests that patient compliance is not significantly impacted until a dosing frequency of three times a day or more.

In summary, there is minimal, if any, evidence to support the use of atenolol over other beta blockers, and this is likely true in any clinical scenario where a beta blocker is indicated. Moreover, given its risk for accumulation and subsequent toxicity in specific patient populations (e.g., older patients, those with renal impairment), the disadvantages of atenolol far outweigh its benefits, which are largely theoretical at best.


P.S., atenolol 50 mg once daily is approximately equal to metoprolol 50 mg twice daily.

References
  1. First International Study of Infarct Survival Collaborative Group. Randomised trial of intravenous atenolol among 16 027 cases of suspected acute myocardial infarction: ISIS-1.  Lancet. 1986 Jul 12;2(8498):57-66. 
  2. Turi ZG, Braunwald E. The use of beta-blockers after myocardial infarction. JAMA. 1983 May 13;249(18):2512-6.
  3. MERIT-HF Investigators. Effect of metoprolol CR/XL in chronic heart failure: Metoprolol CR/XL Randomised Intervention Trial in Congestive Heart Failure (MERIT-HF) Lancet. 1999 Jun 12;353(9169):2001-7.

1 comment:

Sean P. Kane said...

I couldn't agree with you more regarding atenolol! As you mentioned, in younger patients with low risk of AKI (and thus drug accumulation), they usually don't have a compelling indication for atenolol (ie, lone hypertension without comorbidities). In those with true indications for a beta blocker, they often have other risk factors for renal dysfunction that make atenolol a poor selection.

I just found your blog this morning -- very impressive! As a fellow pharmacist, I'm always happy to find professional, evidence-based blogs rather than one complaining about the perils of retail pharmacy. Keep up the good work!