What is the equivalent dosage of metoprolol (Beta-1 selective Beta blocker) when converting from atenolol (Beta-1 selective Beta blocker)?

From the Guidelines

When converting from atenolol to metoprolol, a reasonable approach is to switch from atenolol 25-50 mg once daily to metoprolol tartrate 25-50 mg twice daily or metoprolol succinate (extended-release) 50-100 mg once daily. The conversion is not exact due to differences in potency and pharmacokinetics between these beta-blockers. For patients on atenolol 100 mg daily, consider metoprolol tartrate 50 mg twice daily or metoprolol succinate 100 mg once daily. When making this switch, monitor blood pressure and heart rate closely for 1-2 weeks after conversion to ensure adequate beta-blockade is maintained, as recommended by the 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults 1. The conversion is often necessary because metoprolol has better penetration into the central nervous system and a shorter half-life than atenolol, which is primarily eliminated by the kidneys. This makes metoprolol preferable for patients with declining renal function. Additionally, metoprolol has more evidence supporting its use in heart failure and post-myocardial infarction settings, as seen in the 2013 ACCF/AHA guideline for the management of ST-elevation myocardial infarction 1. When switching, it's best to make the change directly without a tapering period, starting the metoprolol the day after the last atenolol dose to maintain continuous beta-blockade. Some key points to consider when converting between these beta-blockers include:

• Monitoring for signs of heart failure, low output state, or increased risk of cardiogenic shock, as cautioned in the guidelines 1
• Being aware of the potential for prolonged first-degree or high-grade AV block, reactive airways disease, and other contraindications 1
• Understanding the pharmacokinetic and pharmacodynamic properties of metoprolol and atenolol, including their selectivity, partial agonist activity, and usual doses for angina, as outlined in the ACC/AHA 2007 guidelines for the management of patients with unstable angina/non-ST-elevation myocardial infarction 1
• Recognizing the importance of individualizing the dose and monitoring the patient's response, as emphasized in the 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia 1

From the Research

Atenolol Conversion to Metoprolol

• The conversion of atenolol to metoprolol is a common practice in clinical settings, particularly in the treatment of hypertension and heart failure 2.
• However, the choice of beta-blocker is important, as the benefit is not a class-effect, and certain agents are preferred for specific indications 3, 4.
• Metoprolol is a beta-1 selective beta-blocker, similar to atenolol, but with some differences in terms of pharmacokinetics and pharmacodynamics 3.
• The dosage of metoprolol may need to be adjusted when converting from atenolol, taking into account the patient's clinical status and response to treatment 2.
• Studies have shown that metoprolol is effective in reducing mortality and morbidity in patients with heart failure, although the evidence is not consistent across all beta-blockers 5, 4, 6.

Key Considerations

• When switching from atenolol to metoprolol, it is essential to consider the patient's individual characteristics, such as renal function, hepatic function, and concomitant medications 2.
• The dosage of metoprolol should be titrated carefully to achieve the desired therapeutic effect while minimizing adverse reactions 3, 2.
• Metoprolol has been shown to be effective in reducing mortality and morbidity in patients with heart failure, particularly when used in combination with other evidence-based therapies 5, 4, 6.

Comparison with Other Beta-Blockers

• Metoprolol has been compared with other beta-blockers, such as bisoprolol, carvedilol, and nebivolol, in terms of efficacy and safety in patients with heart failure 5, 4, 6.
• The evidence suggests that metoprolol is effective in reducing mortality and morbidity in patients with heart failure, although the magnitude of benefit may vary depending on the specific patient population and clinical context 5, 4, 6.