What is the dosage and management of Metoprolol (metoprolol tartrate) 150 ER for hypertension and angina?

Metoprolol 150 mg Extended-Release: Dosing and Management

Standard Dosing for Hypertension and Angina

For hypertension, metoprolol succinate (extended-release) is initiated at 50-200 mg once daily, with a maximum dose of 400 mg daily, while metoprolol tartrate starts at 25-50 mg twice daily with a maximum of 200 mg daily. 1

Initial Dosing Strategy

• Start with metoprolol succinate 50 mg once daily for most patients with hypertension, titrating upward every 1-2 weeks based on blood pressure response 1
• For angina pectoris, the effective dosage range is 100-400 mg daily, with most patients responding to 100 mg twice daily 1, 2
• A dose of 150 mg extended-release falls within the therapeutic range and represents a moderate-intensity regimen suitable for patients requiring more than initial dosing but not yet at maximum 3

Titration Protocol

• Increase dosage gradually every 1-2 weeks if blood pressure control is not achieved, targeting systolic BP <130 mmHg (ideally lower if tolerated, but not below 120 mmHg) 1
• For angina, titrate to achieve a target resting heart rate of 50-60 beats per minute unless limiting side effects occur 1
• Higher doses (200 mg) show significantly greater exercise tolerance and delayed onset of anginal pain compared to lower doses (50-100 mg), though individual response varies 2

Blood Pressure Reduction Expectations

• Target blood pressure reduction should be at least 20/10 mmHg, ideally to <130/80 mmHg 1
• Metoprolol demonstrates dose-dependent blood pressure lowering, with 200 mg showing greater systolic BP reduction during exercise (168 mmHg) compared to 100 mg (177 mmHg) or 50 mg (177 mmHg) 2
• The duration of antihypertensive effect is longer than expected from the drug's 3-4 hour half-life, making once-daily extended-release formulations effective 3, 4

Monitoring Parameters

Initial Monitoring (First 2-3 Weeks)

• Check blood pressure and heart rate at each visit, watching specifically for symptomatic bradycardia (HR <60 bpm with dizziness) and hypotension (systolic BP <100 mmHg with symptoms) 1
• Listen for new or worsening bronchospasm, particularly in patients with any history of reactive airway disease 1
• Monitor for signs of worsening heart failure, including increased fatigue, shortness of breath, or new rales 1

Ongoing Monitoring

• Clinical response to beta-blockers may be delayed and require 2-3 months to become fully apparent 1
• Monitor for delayed adverse effects like fatigue or weakness, which may appear within 2-3 weeks 1
• Assess for common side effects including hypotension, bradycardia, fatigue, and dizziness 1

Absolute Contraindications

Do not use metoprolol in patients with: 1

• Signs of heart failure, low output state, or increased risk for cardiogenic shock
• PR interval >0.24 seconds, second or third-degree heart block without a pacemaker
• Active asthma or reactive airways disease
• Systolic BP <120 mmHg with sinus tachycardia >110 bpm or heart rate <60 bpm

Critical Warnings

Never Abruptly Discontinue

Abrupt discontinuation of metoprolol can cause severe exacerbation of angina, myocardial infarction, and ventricular arrhythmias, with a 50% mortality rate reported in one study 1

• If dose reduction is needed, reduce by approximately 25-50% every 1-2 weeks 1
• Beta-blocker withdrawal is associated with a 2.7-fold increased risk of 1-year mortality compared to continuous use 1

When to Hold or Reduce Dose

• Hold the dose if systolic blood pressure <100 mmHg with symptoms or heart rate consistently below 45 bpm 1
• Consider reducing dose by 50% rather than complete discontinuation to maintain some beta-blockade benefit in patients with coronary disease or heart failure 1

Pharmacokinetic Considerations

• Metoprolol is primarily metabolized by CYP2D6, with poor metabolizers (8% of Caucasians) exhibiting several-fold higher plasma concentrations 3
• The elimination half-life is 3-4 hours in extensive metabolizers but may be 7-9 hours in poor metabolizers 3
• Hepatic impairment significantly prolongs elimination half-life (up to 7.2 hours), while renal impairment does not require dosage adjustment 3

Special Clinical Scenarios

Acute Hypertensive Situations

• For hypertensive emergencies requiring immediate BP reduction, intravenous metoprolol is given as 2.5-5 mg bolus over 2 minutes, repeated every 5 minutes to a maximum of 15 mg 5
• Oral therapy can be initiated 15 minutes after the last IV dose at 25-50 mg every 6 hours for 48 hours 1

Combination Therapy

• Addition of a diuretic may improve overall response rate in hypertension 6
• For patients with stable ischemic heart disease and hypertension, metoprolol can be combined with ACE inhibitors or ARBs as first-line therapy 5