From the Guidelines
Labetalol and metoprolol tartrate are both beta-blockers used to treat high blood pressure and certain heart conditions, but they have distinct differences in their mechanism of action, usage, and dosing frequency. The primary difference between labetalol and metoprolol tartrate lies in their selectivity and the receptors they block. Labetalol is a non-selective beta-blocker with alpha-blocking properties, blocking beta-1, beta-2, and alpha-1 receptors, making it effective for hypertension, particularly in hypertensive emergencies and pregnancy-related hypertension 1. In contrast, metoprolol tartrate is a selective beta-1 blocker, primarily affecting the heart, which makes it more suitable for patients with respiratory conditions like asthma or COPD, where non-selective beta-blockers might cause bronchospasm.
Key Differences
- Mechanism of Action: Labetalol blocks beta-1, beta-2, and alpha-1 receptors, while metoprolol tartrate primarily blocks beta-1 receptors.
- Usage: Metoprolol is commonly used for hypertension, angina, and after heart attacks, whereas labetalol is often preferred in situations requiring rapid blood pressure control, such as hypertensive emergencies and pregnancy-related hypertension.
- Dosing Frequency: Metoprolol tartrate is typically taken twice daily, and labetalol often requires multiple daily doses, as indicated in the guideline for the prevention, detection, evaluation, and management of high blood pressure in adults 1.
Clinical Implications
Given the differences in their mechanisms of action and usage, the choice between labetalol and metoprolol tartrate should be based on the patient's specific condition and needs. For patients with respiratory conditions, metoprolol tartrate might be a better option due to its selectivity for beta-1 receptors, reducing the risk of bronchospasm. However, for situations requiring rapid blood pressure control or in cases of hypertensive emergencies, labetalol's non-selective beta-blocking and alpha-blocking properties make it a preferred choice. It's also important to consider the dosing frequency and potential side effects when deciding between these medications, as highlighted in the management of chronic heart failure in adults 1.
From the FDA Drug Label
TRANDATE Tablets are adrenergic receptor blocking agents that have both selective alpha1-adrenergic and nonselective beta-adrenergic receptor blocking actions in a single substance Metoprolol Tartrate Injection, USP, is a selective beta 1-adrenoreceptor blocking agent
The main difference between Labetalol and Metoprolol tartrate is that Labetalol has both alpha1-adrenergic and nonselective beta-adrenergic receptor blocking actions, while Metoprolol tartrate is a selective beta 1-adrenoreceptor blocking agent.
- Labetalol blocks both alpha and beta receptors
- Metoprolol tartrate blocks only beta 1 receptors 2 3 3
From the Research
Comparison of Labetalol and Metoprolol
- Labetalol and metoprolol are both used to treat hypertension, but they have different mechanisms of action. Labetalol is a combined alpha- and beta-adrenoceptor blocking agent, while metoprolol is a selective beta1-adrenergic blocker 4, 5.
- In a study comparing the two drugs, labetalol and metoprolol were found to be equally effective in lowering blood pressure in patients with mild to moderate hypertension. However, metoprolol had a greater effect on heart rate 4.
- Labetalol has been shown to be effective in treating various types of hypertension, including essential hypertension, renal hypertension, and pregnancy hypertension 5.
- Metoprolol, on the other hand, has been shown to be effective in treating chronic heart failure, in addition to hypertension 6, 7.
- The side effects of the two drugs also differ. Labetalol has been associated with posture-related dizziness, gastrointestinal disturbances, and tiredness, while metoprolol has been associated with bradycardia, fatigue, and dizziness 4, 5, 7.
Pharmacokinetics and Pharmacodynamics
- Labetalol is readily absorbed after oral administration, but it undergoes significant hepatic first-pass metabolism, resulting in an absolute bioavailability of approximately 25% 5.
- Metoprolol, on the other hand, has a bioavailability of approximately 50% after oral administration 8.
- The elimination half-life of labetalol is approximately 6 hours, while that of metoprolol is approximately 3-4 hours 5, 8.
Clinical Uses
- Labetalol is used to treat hypertension, including essential hypertension, renal hypertension, and pregnancy hypertension 5.
- Metoprolol is used to treat hypertension, chronic heart failure, and angina pectoris 6, 7, 8.
- Metoprolol has been shown to reduce mortality and improve clinical status in patients with chronic heart failure 6, 7.