Metoprolol vs Bisoprolol

## Overview

Metoprolol succinate and bisoprolol are both cardioselective, once-daily beta-blockers with proven mortality benefit in heart failure with reduced ejection fraction (HFrEF). They are the two most similar evidence-based beta-blockers in the HF guidelines.

## Mechanism of Action

Both are highly selective beta-1 adrenoceptor antagonists with minimal beta-2 activity at recommended doses. This selectivity provides cardiovascular benefit while minimizing bronchoconstriction and peripheral vasoconstriction.

## Pharmacokinetics

Bisoprolol has superior bioavailability (~90%) compared to metoprolol succinate XL (~65%), and its elimination is dual (50% hepatic, 50% renal unchanged), providing predictable PK. Bisoprolol's half-life is ~10–12 h, allowing once-daily dosing. Unlike metoprolol, bisoprolol is not significantly metabolized by CYP2D6, avoiding the pharmacogenomic variability that affects metoprolol levels (CYP2D6 poor metabolizers can have 5-fold higher metoprolol exposure).

## Pharmacodynamics and Clinical Evidence

Both have pivotal HFrEF mortality trials: metoprolol (MERIT-HF, 34% reduction in all-cause mortality) and bisoprolol (CIBIS-II, 34% reduction in all-cause mortality). The magnitude of benefit is virtually identical, and guidelines recommend either interchangeably for HFrEF alongside carvedilol.

## Heart Failure Dose Targets

Target doses from the trials: metoprolol succinate 200 mg/day (MERIT-HF); bisoprolol 10 mg/day (CIBIS-II). Both require up-titration starting from low doses.

## Key Takeaways

- Both guideline-recommended for HFrEF with equivalent evidence strength
- Bisoprolol: higher bioavailability, no CYP2D6 PK variability, dual elimination (useful in renal impairment)
- Metoprolol: CYP2D6 metabolized — PK highly variable by genotype
- Both are once-daily options in their extended/standard formulations