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Bedside Snapshot
  • β1-selective beta-blocker (heart > lungs) used IV for rate control in atrial fibrillation/flutter, SVT, and to reduce myocardial oxygen demand in ACS when hemodynamically appropriate.
  • Compared with labetalol: No alpha blockade and more pure heart-rate/contractility reduction. Shorter duration but not as ultra-short-acting as esmolol, so avoid overshooting in tenuous patients.
  • Typical adult IV rate-control dosing: 2.5–5 mg IV over 2 minutes; may repeat every 5 minutes up to a total of 15 mg (commonly 3 doses) as tolerated.
  • ACS (hemodynamically stable STEMI/NSTEMI) classic regimen: 5 mg IV q5 min × 3 (total 15 mg) if HR >60 bpm, SBP >100 mmHg, no signs of acute heart failure or conduction disease, followed by oral metoprolol.
  • Onset IV: ~5 minutes; peak effect 5–10 minutes; duration of effect ~4–6 hours after a few small boluses.
  • Oral immediate-release (tartrate) for step-down: 25–50 mg PO every 6–12 hours, titrated to heart rate and BP. Oral extended-release (succinate) for chronic HF/HTN: typically 25–200 mg PO once daily depending on indication.
  • Avoid or use extreme caution in decompensated heart failure, hypotension, bradycardia, high-grade AV block, and active bronchospasm.
Brand & Generic Names
  • Generic Names: Metoprolol tartrate (IV and immediate-release PO); Metoprolol succinate (extended-release PO)
  • Brand Names: Lopressor (IV/PO IR), Toprol-XL (ER PO), multiple generics
Medication Class

Cardioselective (β1-selective) beta-adrenergic blocker; antianginal, antiarrhythmic, antihypertensive

Pharmacology

Mechanism of Action:

  • Selectively antagonizes β1-adrenergic receptors in the heart at usual doses, decreasing chronotropy, inotropy, and AV nodal conduction, thereby reducing heart rate, myocardial oxygen consumption, and blood pressure
  • At higher doses, β1 selectivity diminishes and some β2 blockade occurs, which can contribute to bronchoconstriction and peripheral vasoconstriction
  • Reduces renin release from juxtaglomerular cells, leading to decreased angiotensin II production and further antihypertensive effect
  • In AF/flutter and other SVTs, slowing AV nodal conduction reduces ventricular rate and can improve diastolic filling and myocardial perfusion

Pharmacokinetics (IV and PO):

  • IV Onset: 5 minutes; peak effect ~5–10 minutes; clinical effect after small bolus doses lasts ~4–6 hours
  • Oral Immediate-Release: Onset ~1 hour, peak effect at ~1.5–2 hours; duration ~6–12 hours depending on dose
  • Oral Extended-Release (succinate): Peak ~6–8 hours; 24-hour duration with once-daily dosing
  • Metabolism: Primarily hepatic via CYP2D6 to inactive metabolites; subject to genetic variability (poor vs extensive metabolizers)
  • Elimination Half-Life: ~3–7 hours (tartrate); prolonged in hepatic impairment and with large or repeated dosing
  • Renal Impairment: Has relatively modest effects on clearance, but dose reduction may still be needed with severe renal and hepatic dysfunction
Indications

IV Metoprolol:

  • Rate control in atrial fibrillation or atrial flutter with rapid ventricular response in hemodynamically stable patients
  • Treatment or prevention of supraventricular tachycardias (e.g., AVNRT) after vagal maneuvers and/or adenosine, when a beta-blocker is appropriate
  • Adjunctive therapy in acute coronary syndromes (STEMI/NSTEMI/unstable angina) to reduce HR, BP, and myocardial oxygen demand in stable patients
  • Control of perioperative or ICU tachycardia associated with pain, agitation, or hyperadrenergic states when more selective β1-blockade is preferred over mixed agents

Chronic Indications (Primarily Oral):

  • Hypertension
  • Angina pectoris
  • Rate control in atrial fibrillation
  • Systolic heart failure (metoprolol succinate for HFrEF)
Dosing & Administration

Available Forms:

  • IV injection (metoprolol tartrate): Typically 1 mg/mL in 5 mL vials (total 5 mg) or similar small vials for slow IV administration
  • Immediate-release oral tablets (tartrate): 25 mg, 37.5 mg, 50 mg, 75 mg, 100 mg strengths (availability varies by region)
  • Extended-release oral tablets (succinate): 25 mg, 50 mg, 100 mg, 200 mg strengths for once-daily dosing

Dosing – Metoprolol Tartrate (Adult, ED/ICU – Always Follow Local Protocol):

Indication Dose & Route Frequency / Titration Notes
AF/flutter or SVT – rate control (hemodynamically stable adult) 2.5–5 mg IV over 2 minutes May repeat q5 minutes up to total 15 mg Hold or reduce dose if SBP <100 mmHg, HR <60, or signs of low output
ACS (STEMI/NSTEMI) – stable patient 5 mg IV over 2 minutes Repeat q5 minutes for total 3 doses (15 mg) as tolerated Then 25–50 mg PO q6–12h; avoid in acute decomp HF, heart block, shock
Perioperative / ICU tachycardia (non-shock, non-HF) 1–5 mg IV over 2 minutes Repeat q5–10 minutes to HR goal Titrate carefully; identify and treat underlying cause of tachycardia
Oral step-down after IV (rate control or ACS) 25–50 mg PO q6–12h (IR) Titrate every 6–12h as needed Convert to ER succinate for chronic HF or once-daily therapy
Chronic HF (metoprolol succinate – outline only) 12.5–25 mg PO daily, titrated Double every 2 weeks as tolerated Target 200 mg PO daily in many HFrEF protocols
Dosing Limits: No single IV bolus >5 mg; total IV 15 mg initially. Adjust by response, age, and LV function. In frail or low EF patients, use lower doses and slow titration.
Contraindications

Contraindications:

  • Severe bradycardia, second- or third-degree AV block, or sick sinus syndrome without a pacemaker
  • Cardiogenic shock or decompensated heart failure (acute pulmonary edema, hypotension)
  • Severe hypotension (e.g., SBP <90 mmHg or MAP poorly tolerated)
  • Severe bronchial asthma or active bronchospasm (relative – consider beta-1 selectivity but risk remains)
  • Known hypersensitivity to metoprolol or other beta-blockers

Major Precautions:

  • COPD or reactive airway disease: Metoprolol is β1-selective, but bronchospasm can still occur; use low doses and monitor
  • Diabetes: May mask adrenergic symptoms of hypoglycemia and blunt response to glucose; emphasize glucose monitoring
  • Peripheral vascular disease: May worsen symptoms of claudication or Raynaud phenomenon
  • Concomitant AV nodal blockers (diltiazem, verapamil, digoxin): Increased risk of bradycardia and AV block
  • Discontinuation: Taper oral therapy over 1–2 weeks when discontinuing chronic use to avoid rebound tachycardia or ischemia
Avoid in Decompensated Heart Failure: Do not use IV metoprolol in patients with acute pulmonary edema, cardiogenic shock, or signs of severe decompensation. Beta-blockade can worsen contractility and precipitate cardiovascular collapse in this setting.
Bradycardia & AV Block Risk: Metoprolol slows AV nodal conduction and can cause severe bradycardia, high-grade AV block, or asystole, especially when combined with other AV nodal blockers (diltiazem, verapamil, digoxin). Monitor ECG continuously during IV administration.
Adverse Effects

Common:

  • Bradycardia, fatigue, dizziness
  • Mild hypotension, orthostasis
  • Cold extremities, exercise intolerance
  • GI upset (nausea, diarrhea)

Serious:

  • Severe bradycardia, high-grade AV block, asystole
  • Acute decompensation of heart failure or cardiogenic shock
  • Bronchospasm in susceptible individuals
  • Worsening peripheral ischemia in severe PAD
  • Masking of hypoglycemic symptoms in diabetics
Special Populations

Elderly Patients:

  • Increased sensitivity to beta-blocker effects
  • Use lower initial doses (1–2.5 mg IV, 12.5–25 mg PO)
  • Titrate slowly with close hemodynamic monitoring

Hepatic Impairment:

  • Metoprolol is extensively metabolized by the liver
  • Reduce doses and increase dosing intervals in severe hepatic disease
  • Monitor for prolonged effects and increased drug levels

Renal Impairment:

  • No significant dose adjustment needed for mild-moderate renal impairment
  • Consider dose reduction in severe renal dysfunction combined with hepatic disease

Pregnancy & Lactation:

  • Pregnancy Category C: Use only if benefits outweigh risks
  • May cause fetal bradycardia, hypoglycemia, and growth restriction
  • Monitor fetus closely if metoprolol is used during pregnancy
  • Lactation: Excreted in breast milk in small amounts; generally considered compatible with breastfeeding but monitor infant

Diabetes:

  • Beta-blockers can mask symptoms of hypoglycemia (tachycardia, tremor)
  • May blunt counterregulatory response to hypoglycemia
  • Emphasize frequent blood glucose monitoring
  • β1-selective agents like metoprolol preferred over non-selective beta-blockers
Monitoring

During IV Administration:

  • Continuous ECG monitoring for heart rate, rhythm, and conduction abnormalities
  • Frequent blood pressure monitoring (every 2–5 minutes during IV dosing)
  • Heart rate and rhythm for bradycardia, pauses, or new AV block
  • Signs of heart failure (pulmonary edema, rising lactate, low urine output)

General Monitoring:

  • Respiratory status and wheeze in any patient with reactive airway disease
  • Blood glucose trends in diabetics or patients on insulin/secretagogues
  • Peripheral perfusion and symptoms in patients with PAD
Clinical Pearls
Small, Spaced Boluses for AF with RVR: For AF with RVR, think about loading in small, spaced boluses (e.g., 2.5–5 mg IV q5–10 min) rather than a single large slug to avoid crashing borderline patients. This allows you to titrate to effect and stop before overshooting.
ACS Beta-Blockade Has Changed: In ACS, beta-blockade should be reserved for patients who are not hypotensive, bradycardic, or in acute heart failure. The era of reflexively giving IV metoprolol to every STEMI has passed. Current guidelines emphasize hemodynamic stability first.
Consider Esmolol for Tight Titration: If you need tight, minute-to-minute titration (e.g., septic shock with tachycardia), consider esmolol rather than metoprolol. Esmolol's ultra-short half-life allows for rapid on/off control, while metoprolol commits you to 4–6 hours of effect.
Treat the Underlying Cause: Always identify and treat the underlying cause of tachycardia (pain, hypovolemia, hypoxia, fever, sepsis) before or alongside beta-blockade. Beta-blockers don't fix the problem – they just mask the compensatory response. Address the root cause first.
β1-Selectivity Is Dose-Dependent: Metoprolol's β1-selectivity diminishes at higher doses. At low doses (2.5–5 mg IV), it preferentially blocks cardiac β1 receptors. At higher cumulative doses, β2 blockade increases, raising the risk of bronchospasm in susceptible patients.
Avoid Abrupt Discontinuation: Don't stop chronic beta-blocker therapy abruptly, especially in patients with CAD or heart failure. Taper over 1–2 weeks to avoid rebound tachycardia, hypertension, or acute coronary syndrome. Sudden withdrawal can precipitate MI or arrhythmias.
Succinate for HFrEF, Tartrate for Acute: For chronic systolic heart failure (HFrEF), use metoprolol succinate (extended-release) titrated up slowly. For acute ED/ICU rate control or ACS, use metoprolol tartrate (immediate-release) IV or PO. They're not interchangeable.
Combination with Calcium Channel Blockers: Be very cautious when combining metoprolol with non-dihydropyridine calcium channel blockers (diltiazem, verapamil). Both slow AV conduction and depress contractility. The combination can cause severe bradycardia, heart block, or heart failure decompensation.
References
  • 1. Lexicomp. (2025). Metoprolol: Drug information. Wolters Kluwer. https://online.lexi.com/
  • 2. DrugBank Online. (2024). Metoprolol (DB00264). https://go.drugbank.com/drugs/DB00264
  • 3. January, C. T., Wann, L. S., Calkins, H., Chen, L. Y., Cigarroa, J. E., Cleveland, J. C., Ellinor, P. T., Ezekowitz, M. D., Field, M. E., Furie, K. L., Heidenreich, P. A., Murray, K. T., Shea, J. B., Tracy, C. M., & Yancy, C. W. (2019). 2019 AHA/ACC/HRS focused update of the 2014 AHA/ACC/HRS guideline for the management of patients with atrial fibrillation. Circulation, 140(2), e125–e151. https://doi.org/10.1161/CIR.0000000000000665
  • 4. O'Gara, P. T., Kushner, F. G., Ascheim, D. D., Casey, D. E., Chung, M. K., de Lemos, J. A., Ettinger, S. M., Fang, J. C., Fesmire, F. M., Franklin, B. A., Granger, C. B., Krumholz, H. M., Linderbaum, J. A., Morrow, D. A., Newby, L. K., Ornato, J. P., Ou, N., Radford, M. J., Tamis-Holland, J. E., ... Zhao, D. X. (2013). 2013 ACCF/AHA guideline for the management of ST-elevation myocardial infarction. Circulation, 127(4), e362–e425. https://doi.org/10.1161/CIR.0b013e3182742cf6
  • 5. Farkas, J. (2023). Atrial fibrillation. EMCrit Project – Internet Book of Critical Care (IBCC). https://emcrit.org/ibcc/af/
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