Which beta blocker, metoprolol or carvedilol, is more effective in controlling tachycardia with minimal hypotensive effects?

From the Guidelines

Metoprolol is generally better for heart rate control in tachycardia with less hypotensive effects compared to carvedilol. Metoprolol is a selective beta-1 blocker that primarily targets receptors in the heart, making it more specific for controlling heart rate while having less impact on blood pressure 1. Typical dosing starts at 25-50 mg twice daily, which can be titrated up to 100-200 mg daily as needed. Carvedilol, being a non-selective beta-blocker with additional alpha-blocking properties, provides more pronounced blood pressure reduction due to its vasodilatory effects. This makes carvedilol more likely to cause hypotension, especially when initiating therapy.

Key Considerations

• When using metoprolol for tachycardia, start with lower doses and monitor heart rate response, gradually increasing as needed while watching for bradycardia.
• The selective nature of metoprolol also means fewer bronchospastic effects in patients with respiratory conditions compared to non-selective agents like carvedilol.
• Individual patient factors including comorbidities (particularly if the patient has heart failure, where carvedilol may offer mortality benefits) should guide the final selection between these medications 1.

Dosage and Administration

• Metoprolol tartrate: 100–200 mg daily, divided into two doses 1.
• Metoprolol succinate: 50–200 mg daily, given once daily 1.
• Carvedilol: 12.5–50 mg daily, divided into two doses 1.

Special Considerations

• Patients with marked first-degree AV block, any form of second- or third-degree AV block, a history of asthma, severe LV dysfunction or HF, or at high risk for shock should not receive beta blockers on an acute basis 1.
• Patients with evidence of a low-output state or sinus tachycardia should not receive acute beta-blocker therapy until these conditions have resolved 1.

From the Research

Comparison of Metoprolol and Carvedilol

• Metoprolol is a beta(1)-selective beta-adrenergic antagonist, while carvedilol is a non-selective beta-blocker with additional blockades of alpha(1)-adrenoceptors 2.
• Carvedilol has been shown to cause less decrease in heart rate at rest compared to metoprolol, but has a similar effect on heart rate during exercise 2.
• The beta-blocking effects of carvedilol are more pronounced during exercise, although metoprolol tends to decrease heart rate to a greater extent [-21%, -25%, and -24% vs -16%, -16%, and -18%] 2.

Effects on Blood Pressure

• Carvedilol reduces peripheral vascular resistance by blocking arterial alpha 1-adrenoceptors, producing vasodilation, while preventing reflex tachycardia by blocking cardiac beta 1- and beta 2-adrenoceptors 3.
• The blood pressure lowering efficacy of carvedilol has been shown to be -4 mm Hg (95% confidence intervals -6 to -2)/-3 mm Hg (95% CI -4 to -2) 4.

Clinical Outcomes

• A study comparing metoprolol and carvedilol in patients with acute myocardial infarction found that overall survival was similar, but may be superior for carvedilol in patients with left ventricular ejection fraction ≤40% 5.
• A review of beta-blocker treatment of chronic heart failure found that carvedilol may be superior to metoprolol in improving left ventricular ejection fraction, but there is no conclusive evidence that carvedilol is superior to metoprolol in terms of prognosis 6.

Tolerability and Side Effects

• Carvedilol has been shown to have a more favorable side effect profile compared to metoprolol, with less effect on beta-adrenergic responsiveness and exercise tolerance in heart-failure patients 6.
• The risk of withdrawal due to adverse effects was found to be similar for carvedilol and metoprolol, with a risk ratio of 0.88 (95% CI 0.54 to 1.42) 4.