What is the typical dosage and management of Metoprolol (beta-blocker) ER 100?

Metoprolol ER 100 mg: Dosing and Management

Metoprolol succinate (extended-release) 100 mg once daily is an appropriate mid-range dose for hypertension, angina, and heart failure, with the option to titrate up to 200 mg daily for hypertension or 400 mg daily for heart failure if needed for adequate control. 1, 2

Standard Dosing by Indication

Hypertension

• Initial dose: 50-100 mg once daily 1, 2
• Your current dose of 100 mg ER: This is within the therapeutic range and can be maintained if blood pressure is controlled 1
• Maximum dose: 400 mg daily 1, 2
• Titration: Increase gradually every 1-2 weeks if blood pressure control is inadequate 1
• Target: Blood pressure reduction of at least 20/10 mmHg, ideally to <140/90 mmHg 1, 2

Angina Pectoris

• Dose range: 50-200 mg once daily for extended-release formulation 3
• Target heart rate: 50-60 beats per minute at rest unless limiting side effects occur 3, 1

Heart Failure with Reduced Ejection Fraction

• Initial dose: 12.5-25 mg once daily (start low) 1
• Target dose: 200 mg once daily 1
• Mean effective dose: 159 mg daily 1

Pharmacokinetics of Extended-Release Formulation

The controlled-release metoprolol succinate provides several advantages over immediate-release metoprolol tartrate:

• Duration of action: Approximately 20 hours of sustained drug release from individual pellets 4
• Plasma concentration: More constant levels with reduced peak-to-trough fluctuations compared to immediate-release 5, 6
• Beta-1 selectivity: Better maintained throughout the dosing interval due to avoidance of high peak concentrations 6
• Dosing frequency: Once daily administration is appropriate and effective 5, 7

Absolute Contraindications

Do not administer metoprolol if any of the following are present:

• Signs of heart failure, low output state, or increased risk for cardiogenic shock 1, 2
• PR interval >0.24 seconds 1, 2
• Second or third-degree heart block without a functioning pacemaker 1, 2
• Active asthma or reactive airways disease 1, 2
• Decompensated heart failure 1, 2

Risk Factors for Cardiogenic Shock

Be particularly cautious in patients with:

• Age >70 years 1, 2
• Systolic blood pressure <120 mmHg 1, 2
• Sinus tachycardia >110 bpm or heart rate <60 bpm 1, 2
• Increased time since symptom onset (in acute MI setting) 1, 2

Monitoring Parameters

At Each Visit

• Blood pressure and heart rate: Check at every visit 1
• Target resting heart rate: 50-60 bpm unless limiting side effects 3, 1
• Signs of worsening heart failure: Monitor for increased fatigue, shortness of breath, or pulmonary rales 1
• Bronchospasm: Particularly during initiation 1, 2

Common Adverse Effects

• Hypotension 1
• Bradycardia 1
• Fatigue 1
• Dizziness 1

Special Populations

Hepatic Impairment

• Metoprolol is primarily eliminated by hepatic metabolism via CYP2D6 8
• Elimination half-life: Can be prolonged up to 7.2 hours in severe hepatic impairment 8
• Recommendation: Initiate at low doses with cautious gradual titration 8

Renal Impairment

• No dose adjustment required 8
• Systemic availability and half-life do not differ clinically from normal subjects 8

Geriatric Patients (>65 years)

• Use a low initial starting dose given greater frequency of decreased hepatic, renal, or cardiac function 8
• Slightly higher plasma concentrations may occur due to decreased metabolism and hepatic blood flow, but this is not clinically significant 8

CYP2D6 Poor Metabolizers (~8% of Caucasians)

• Exhibit several-fold higher plasma concentrations 8
• Half-life may be 7-9 hours (vs. 3-4 hours in extensive metabolizers) 8
• This decreases metoprolol's cardioselectivity 8

Critical Clinical Pitfalls

Never Abruptly Discontinue

• Avoid abrupt cessation to prevent rebound hypertension or worsening angina 1, 2
• Tapering protocol: Reduce dose by 25-50% every 1-2 weeks 1
• Monitor for worsening heart failure symptoms during tapering 1

Avoid IV Metoprolol in High-Risk Acute MI

• The COMMIT trial (45,852 patients) showed early IV metoprolol increased cardiogenic shock risk, particularly in the first 24 hours 3, 2
• While it reduced reinfarction and ventricular fibrillation after day 1, the early shock risk counterbalanced this benefit 3
• Recommendation: Initiate orally within the first 24 hours in stable patients without contraindications 3

Equivalency Note

• 100 mg metoprolol succinate ER contains 95 mg of metoprolol succinate salt 4
• This is considered equivalent to 100 mg metoprolol tartrate 4