Therapeutic Drug Exchange for Metoprolol Succinate from Atenolol
When switching from atenolol to metoprolol succinate, use a 1:2 ratio where 50 mg of atenolol is equivalent to approximately 100 mg of metoprolol succinate once daily. 1, 2
Conversion Rationale and Evidence
The conversion between atenolol and metoprolol succinate requires understanding their relative potency and pharmacokinetic differences:
- Metoprolol succinate (extended-release) is designed to provide constant plasma concentrations over 20 hours, allowing for once-daily dosing 2
- A 100 mg metoprolol succinate tablet contains 95 mg of metoprolol succinate and is considered equivalent to 100 mg of metoprolol tartrate 2
- Clinical studies have shown that 50 mg of atenolol once daily provides similar blood pressure control to 100 mg of metoprolol 3, 4
Conversion Algorithm
Calculate equivalent dose:
- 25 mg atenolol ≈ 50 mg metoprolol succinate
- 50 mg atenolol ≈ 100 mg metoprolol succinate
- 100 mg atenolol ≈ 200 mg metoprolol succinate
Initial dosing considerations:
- Start with metoprolol succinate 50-100 mg once daily when converting from atenolol 25-50 mg
- Maximum daily dose of metoprolol succinate is 400 mg once daily 5
- Metoprolol succinate is available in 25,50,100, and 200 mg tablets
Clinical Monitoring After Conversion
- Monitor blood pressure and heart rate within 1-2 weeks after conversion
- Target heart rate of 50-60 beats per minute unless limiting side effects occur 5
- Pay particular attention to early morning blood pressure control (12 AM-6 AM), as metoprolol succinate may provide better 24-hour coverage than atenolol 6
Important Clinical Considerations
- Metoprolol succinate has been shown to provide more consistent 24-hour blood pressure control compared to atenolol, particularly in the early morning hours when cardiovascular risk is highest 6
- Atenolol has a longer half-life (6-7 hours) compared to immediate-release metoprolol (3-4 hours), but metoprolol succinate's extended-release formulation overcomes this difference 2, 7
- Both medications are cardioselective beta-blockers, but at higher doses, this selectivity may be lost
- Consider patient comorbidities when selecting the appropriate beta-blocker and dosage
Common Pitfalls to Avoid
- Do not confuse metoprolol succinate (extended-release, once daily) with metoprolol tartrate (immediate-release, twice daily)
- Avoid abrupt discontinuation of either beta-blocker, which can lead to rebound hypertension or exacerbation of angina
- Remember that metoprolol succinate tablets should be swallowed whole and not crushed or chewed
- Be aware that some patients may require dose adjustments based on individual response and tolerability
By following this conversion approach, you can effectively transition patients from atenolol to metoprolol succinate while maintaining adequate blood pressure control and minimizing adverse effects.