Metoprolol Tartrate to Succinate Conversion
The equivalent dose of metoprolol succinate for a patient taking Lopressor (metoprolol tartrate) 12.5 mg twice daily is 25 mg once daily of metoprolol succinate.
Conversion Rationale
Metoprolol is available in two salt formulations with different pharmacokinetic properties:
Metoprolol tartrate (Lopressor):
- Immediate-release formulation
- Typically dosed twice daily due to shorter half-life
- Used for hypertension, angina, and post-MI patients
Metoprolol succinate (Toprol XL):
- Extended-release/controlled-release formulation
- Once-daily dosing
- Provides more consistent plasma concentrations over 24 hours
Dose Equivalence
- A 100 mg metoprolol succinate (CR/XL) tablet contains 95 mg of metoprolol succinate and is equivalent to 100 mg of metoprolol tartrate 1
- Therefore, the conversion is essentially 1:1 in terms of total daily dose
Calculation
- Current regimen: Metoprolol tartrate 12.5 mg BID = 25 mg total daily dose
- Equivalent metoprolol succinate dose: 25 mg once daily
Clinical Considerations
Advantages of Switching to Succinate
- Improved adherence: Once-daily dosing improves medication compliance 2
- More consistent beta-blockade: The controlled-release formulation provides more stable plasma concentrations over 24 hours
- Reduced peak-related side effects: Less pronounced peak concentrations may reduce side effects
Special Populations
- Heart failure patients: Metoprolol succinate is specifically indicated for heart failure based on clinical trials, with target dose of 200 mg once daily 2, 3
- Elderly or frail patients: May be more sensitive to beta-blocker effects; careful monitoring is recommended
Monitoring After Conversion
- Blood pressure: Monitor for adequate control
- Heart rate: Target heart rate of 60-80 bpm at rest and <110 bpm with moderate activity 2
- Symptoms: Watch for signs of excessive beta-blockade (fatigue, dizziness, bradycardia)
Common Pitfalls to Avoid
- Abrupt discontinuation: Never stop beta-blockers suddenly; this can lead to rebound hypertension or angina
- Confusion between formulations: Always specify "succinate" or "tartrate" when prescribing to avoid medication errors
- Underdosing: If the patient was well-controlled on tartrate, maintain the equivalent total daily dose when switching to succinate
When transitioning from twice-daily metoprolol tartrate to once-daily metoprolol succinate, the total daily dose remains the same, but the administration changes from divided doses to a single daily dose.