What carvedilol dose is equivalent to metoprolol (tartrate or succinate) in an adult with chronic heart failure or post‑myocardial infarction left‑ventricular dysfunction, and how should the conversion be performed?

Metoprolol to Carvedilol Conversion in Heart Failure

There is no established dose equivalency between metoprolol and carvedilol for heart failure, and direct conversion is not recommended—instead, carvedilol should be initiated at its standard starting dose (3.125 mg twice daily) after metoprolol is discontinued or tapered. 1, 2

Why Direct Conversion Is Not Appropriate

The critical issue is that metoprolol tartrate and carvedilol were compared at doses that were not equivalent in the only head-to-head mortality trial. 1 The COMET trial used metoprolol tartrate 50 mg twice daily versus carvedilol 25 mg twice daily, and carvedilol demonstrated superior mortality reduction—but this comparison has been criticized because:

• Metoprolol tartrate (immediate-release) is not the formulation proven to reduce mortality in heart failure. 1, 3, 4
• The dose of metoprolol tartrate used in COMET may have been inadequate based on prior studies. 3, 4
• Metoprolol succinate (extended-release) at 200 mg once daily is the evidence-based formulation for heart failure, not metoprolol tartrate. 1, 2

Evidence-Based Approach to Switching

If Patient Is on Metoprolol Succinate

1. Do not attempt dose conversion. There are no trials comparing carvedilol to metoprolol succinate at equivalent doses, and the relative efficacy between these two agents is unknown. 1

2. If switching is clinically necessary (e.g., patient-specific factors favoring carvedilol):

   • Taper metoprolol succinate gradually over 1-2 weeks to avoid rebound effects. 2
   • Start carvedilol at 3.125 mg twice daily (the standard starting dose for heart failure). 1
   • Titrate carvedilol by doubling the dose every 2 weeks if tolerated, targeting 25 mg twice daily. 1

If Patient Is on Metoprolol Tartrate

• Metoprolol tartrate is not the evidence-based formulation for heart failure. 1, 2, 4
• Consider switching to either metoprolol succinate 200 mg once daily OR carvedilol 25 mg twice daily—both are proven to reduce mortality. 1, 2
• If switching to carvedilol, follow the same initiation protocol: start at 3.125 mg twice daily and titrate upward. 1

Pharmacologic Differences That Preclude Simple Conversion

Receptor Selectivity

• Carvedilol is a nonselective beta-blocker (blocks beta-1, beta-2, and alpha-1 receptors) at all clinically relevant doses. 5
• Metoprolol succinate is beta-1 selective at low doses but becomes progressively nonselective at higher doses (≥200 mg). 5
• These pharmacodynamic differences mean the drugs cannot be considered interchangeable on a milligram-per-milligram basis. 3, 4

Pharmacokinetics

• Carvedilol is inherently long-acting with twice-daily dosing. 3
• Metoprolol succinate is formulated as extended-release for once-daily dosing. 2, 3
• Metoprolol tartrate is short-acting and requires twice-daily dosing. 2, 3

Monitoring During Transition

During carvedilol initiation and titration, monitor for: 2

• Heart failure symptoms and fluid retention (increase diuretics or ACE inhibitors before reducing beta-blocker dose if symptoms worsen)
• Symptomatic hypotension (systolic BP <85 mmHg)
• Symptomatic bradycardia
• Worsening renal function

Common Pitfalls to Avoid

• Never assume beta-blockers are a class effect. Only bisoprolol, metoprolol succinate, and carvedilol have proven mortality benefit in heart failure. 1
• Do not use metoprolol tartrate as a substitute for metoprolol succinate in heart failure—they are different formulations with different evidence bases. 1, 2, 4
• Never abruptly discontinue either beta-blocker, as this may precipitate angina, myocardial infarction, or arrhythmias. 2
• Do not extrapolate COMET trial results (carvedilol vs. metoprolol tartrate) to metoprolol succinate—they are pharmacologically distinct. 3, 4

Most Recent Comparative Evidence

The 2015 Carvedilol or Metoprolol Evaluation Study (COMES) compared carvedilol to metoprolol succinate at equivalent doses in 4,016 patients with chronic heart failure. 6 After propensity score matching and dose adjustment, there was no difference in all-cause mortality between carvedilol and metoprolol succinate (HR 1.00,95% CI 0.82-1.23, P=0.99). 6 This suggests that when both drugs are used at their evidence-based target doses, they provide similar survival benefit.