What is the recommended dosage and treatment protocol for Metoprolol (beta-blocker) in patients with hypertension or heart-related conditions?

Metoprolol Dosing and Treatment Protocol

Initial Dosing for Hypertension

For hypertension, start metoprolol tartrate at 25-50 mg twice daily or metoprolol succinate (extended-release) at 50-100 mg once daily, titrating to a maximum of 200 mg daily for tartrate or 400 mg daily for succinate. 1

• The immediate-release formulation (tartrate) requires twice-daily dosing due to its 3-4 hour half-life, while the extended-release formulation (succinate) allows once-daily administration 2
• Titrate the dose gradually every 1-2 weeks if blood pressure control is not achieved, targeting a reduction of at least 20/10 mmHg to ideally <140/90 mmHg 1
• Monitor blood pressure and heart rate at each visit during titration 1

Acute Myocardial Infarction Protocol

In acute MI, administer 5 mg IV over 1-2 minutes, repeated every 5 minutes for up to 3 doses (maximum 15 mg total), then transition to oral therapy 15 minutes after the last IV dose. 1, 2

Critical Contraindications Before IV Administration

Do not give IV metoprolol if any of the following are present:

• Signs of heart failure, low output state, or cardiogenic shock risk 1
• Systolic BP <120 mmHg 1
• Heart rate >110 bpm or <60 bpm 1
• PR interval >0.24 seconds or second/third-degree heart block 1
• Active asthma or reactive airway disease 1
• Age >70 years with multiple risk factors 1

Transition to Oral Therapy

• Start metoprolol tartrate 50 mg every 6 hours for patients tolerating the full IV dose, beginning 15 minutes after the last IV dose and continuing for 48 hours 2
• For patients with partial intolerance, use 25 mg every 6 hours 2
• After 48 hours, transition to maintenance dosing of 100 mg twice daily 2

Atrial Fibrillation Rate Control

For acute rate control in stable atrial fibrillation with rapid ventricular response, give metoprolol 5 mg IV every 5 minutes up to 3 doses (maximum 15 mg) until heart rate <110 bpm. 1

• Never administer the full 15 mg as a single rapid bolus, as this significantly increases hypotension and bradycardia risk 1
• Avoid in pre-excited atrial fibrillation (WPW syndrome), as it may paradoxically accelerate ventricular response 1
• For chronic rate control, use metoprolol tartrate 25-100 mg twice daily or metoprolol succinate 50-400 mg once daily 1
• Target resting heart rate of 50-60 bpm unless limiting side effects occur 1

Heart Failure with Reduced Ejection Fraction

In HFrEF, start metoprolol succinate at 12.5-25 mg once daily and titrate slowly to a target dose of 200 mg once daily. 1

• Metoprolol succinate is the preferred formulation for heart failure, not metoprolol tartrate 3
• The mean effective dose in clinical trials was 159 mg daily 1
• Titrate slowly over weeks to months, as clinical response may take 2-3 months to become fully apparent 1
• Women may achieve optimal outcomes at 50% of guideline-recommended doses due to 50-80% higher drug exposure compared to men 1

Frequent PVCs

For PVC suppression, start metoprolol tartrate at 25 mg twice daily, with a maximum of 200 mg twice daily if needed for symptom control. 1

• For extended-release formulation, start at 50 mg once daily with a maximum of 400 mg daily 1
• Avoid in patients with AV block greater than first degree, SA node dysfunction, decompensated heart failure, hypotension, reactive airway disease, or cardiogenic shock 1

Oral to IV Conversion

When converting from oral to IV metoprolol, do not use mathematical conversion—instead, start with 2.5-5 mg IV bolus over 2 minutes, repeating every 5 minutes as needed based on hemodynamic response, with a maximum total dose of 15 mg. 1

• This conservative approach is necessary because oral bioavailability is only 50% due to first-pass metabolism, but the relationship is not linear 2
• Transition back to oral therapy 15 minutes after the last IV dose, starting with metoprolol tartrate 25-50 mg every 6 hours for 48 hours before returning to extended-release formulations 1

Management of Symptomatic Bradycardia

If heart rate drops below 50 bpm with symptoms (dizziness, lightheadedness, hypotension), reduce the metoprolol dose by 50% rather than discontinuing completely. 1

When to Hold Metoprolol Completely

• Heart rate consistently <45 bpm 1
• Systolic BP <100 mmHg with symptoms of hypoperfusion 1
• Signs of decompensated heart failure 1
• Acute altered mental status or signs of shock 1

Critical Warning About Abrupt Discontinuation

Never abruptly discontinue metoprolol, as this can cause severe exacerbation of angina, myocardial infarction, and ventricular arrhythmias, with a 50% mortality rate reported in one study and a 2.7-fold increased risk of 1-year mortality compared to continuous use 1, 3

Tapering Protocol

When discontinuing metoprolol, reduce the dose by 25-50% every 1-2 weeks. 1

• Monitor for worsening heart failure symptoms (increased fatigue, shortness of breath, edema, weight gain) during tapering 1
• If symptoms worsen, return to the previous dose before attempting a more gradual taper 1
• For heart failure patients, use smaller incremental reductions and consider temporarily increasing diuretics or ACE inhibitors if decompensation occurs 1

Special Populations

Hepatic Impairment

Initiate metoprolol at low doses with cautious gradual titration in patients with hepatic impairment, as elimination half-life can be prolonged up to 7.2 hours depending on severity 2

Renal Impairment

No dose adjustment is required in patients with renal impairment 2

Geriatric Patients

Start with low initial doses in elderly patients due to decreased hepatic function and blood flow, though plasma concentration increases are not typically clinically significant 2

Women

Consider using 50% of standard guideline-recommended doses in women, as metoprolol exposure is 50-80% higher in women than men, resulting in greater heart rate and blood pressure reduction 1

Monitoring Parameters

During IV Administration

• Continuous ECG monitoring 1
• Frequent blood pressure and heart rate checks 1
• Auscultation for new rales (pulmonary congestion) 1
• Auscultation for bronchospasm 1

During Oral Therapy

• Blood pressure and heart rate at each visit 1
• Signs of worsening heart failure or bronchospasm, particularly during initiation 1
• Target resting heart rate of 50-60 bpm unless limiting side effects occur 1
• Watch for delayed adverse effects like fatigue or weakness within 2-3 weeks 1

Common Adverse Effects

• Hypotension 1
• Bradycardia 1
• Fatigue 1
• Dizziness 1
• Bronchospasm (particularly in patients with reactive airway disease) 1

Key Clinical Pearls

• Metoprolol is beta-1 selective at lower doses, making it preferred over non-selective beta-blockers like propranolol in patients with respiratory conditions 3
• Cardioselectivity is lost at higher doses and in poor CYP2D6 metabolizers (8% of Caucasians, 2% of other populations), who exhibit several-fold higher plasma concentrations 2
• Poor metabolizers have elimination half-lives of 7-9 hours compared to 3-4 hours in extensive metabolizers 2
• Some beta-blocker is better than no beta-blocker—maintain therapy at reduced doses rather than discontinuing when possible 1