From the Guidelines
For an 81-year-old male patient experiencing occasional low blood pressure and bradycardia (heart rate in the 50s) while on metoprolol tartrate 50mg, I recommend switching to metoprolol succinate 25mg once daily. This recommendation is based on the guidelines provided by the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society, as outlined in the 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia 1. The conversion from metoprolol tartrate to metoprolol succinate typically follows a 1:1 ratio for total daily dose, but in this case, a dose reduction is warranted due to the adverse effects of bradycardia and hypotension.
Key Considerations
- The patient's current symptoms of occasional low blood pressure and bradycardia (heart rate in the 50s) suggest that the current dose of metoprolol tartrate may be too high, leading to these adverse effects.
- Metoprolol succinate is an extended-release formulation that provides more consistent blood levels throughout the day compared to the immediate-release tartrate form, which may help minimize the peaks in drug concentration that could be contributing to the symptomatic episodes of low heart rate and blood pressure.
- According to the guidelines, the initial daily dose of metoprolol succinate is 50 mg QD, but given the patient's age and symptoms, starting with a lower dose of 25mg once daily is a more cautious approach to avoid exacerbating bradycardia and hypotension.
- The maximum total daily maintenance dose of metoprolol succinate is 400 mg QD, but this patient will be started on a much lower dose due to his sensitive response to beta-blockers, as indicated by his current symptoms 1.
Monitoring and Follow-Up
After making this change, the patient should monitor his blood pressure and heart rate regularly and follow up within 1-2 weeks to assess response. If bradycardia or hypotension persists even at this lower dose, further dose reduction or discontinuation may be necessary. The patient's response to the medication and any potential side effects should be closely monitored to ensure the best possible outcome in terms of morbidity, mortality, and quality of life.
From the FDA Drug Label
DOSAGE & ADMINISTRATION ... In patients with severe intolerance, discontinue metoprolol tartrate ... Geriatric Patients (>65 years) In general, use a low initial starting dose in elderly patients given their greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.
The patient is currently on metoprolol tartrate 50mg. To adjust to metoprolol succinate, the dosage is typically converted to 100-200mg of metoprolol succinate once daily, as metoprolol succinate is an extended-release formulation. However, given the patient's age (81y/o), occasionally low blood pressure, and heart rate in the 50s, a more cautious approach is warranted.
- The initial dose of metoprolol succinate should be lowered to 25-50mg once daily, with careful monitoring of blood pressure and heart rate.
- The frequency of administration should be once daily, due to the extended-release formulation of metoprolol succinate.
- Close monitoring of the patient's condition is necessary, and the dose may need to be adjusted based on the patient's response to the medication 2.
From the Research
Metoprolol Tartrate to Metoprolol Succinate Conversion
- The conversion from metoprolol tartrate to metoprolol succinate is based on the equivalent beta-blocking effect, with the succinate form being more long-acting 3.
- The general conversion ratio is 1:1 for metoprolol tartrate to metoprolol succinate in terms of beta-blocking effect, but the succinate form is usually administered once daily due to its longer half-life.
Dosing Adjustment for Metoprolol Succinate
- For an 81-year-old patient with occasionally low blood pressure and a heart rate in the 50s, currently on metoprolol tartrate 50mg, the equivalent dose of metoprolol succinate would be around 50-100mg once daily, considering the patient's age and potential sensitivity to beta-blockers 4.
- However, the optimal dose of metoprolol succinate for this patient should be determined based on individual response and tolerance, with careful monitoring of blood pressure and heart rate.
- Studies have shown that higher doses of metoprolol succinate (up to 190mg) can be effective in controlling heart rate and reducing mortality in patients with heart failure, but may not be necessary or suitable for all patients 5, 6.
Frequency of Administration
- Metoprolol succinate is typically administered once daily, due to its long-acting formulation 3.
- The patient's dose can be adjusted based on individual response and tolerance, with careful monitoring of blood pressure and heart rate, and the frequency of administration can remain once daily.