metoprolol

Metoprolol is a selective beta-1 adrenergic receptor blocker used to treat several cardiovascular conditions, including hypertension, angina pectoris, certain arrhythmias, and heart failure with reduced ejection fraction. It is also prescribed after myocardial infarction to reduce mortality. Brand names include Lopressor (tartrate) and Toprol-XL (succinate).

Mechanism and effects: Metoprolol reduces heart rate, myocardial contractility, and AV nodal conduction, leading to lower cardiac output and blood pressure. By decreasing renin release, it can further reduce blood pressure and myocardial oxygen demand. The drug is relatively cardioselective at standard doses, but selectivity may lessen at higher doses.

Formulations and pharmacokinetics: Metoprolol is available as tartrate (short-acting) and succinate (extended-release). It can be taken orally or given by intravenous injection in hospital settings. Metoprolol is largely metabolized in the liver and excreted by the kidneys; pharmacokinetic parameters vary with formulation and patient factors.

Dosing and administration: Dosing is individualized based on indication, response, tolerability, and formulation. Tartrate is typically used for short-term treatment and may require more frequent dosing, while succinate is designed for once-daily administration. Titration should be gradual to minimize adverse effects. Use with caution in patients with symptomatic bradycardia, advanced heart block, decompensated heart failure, or severe hypotension.

Contraindications and cautions: Contraindicated in significant bradycardia, second- or third-degree heart block, cardiogenic shock, and decompensated heart failure requiring intravenous inotropic support. Caution is advised in asthma or COPD, diabetes (hypoglycemia masking), and during concurrent use with other antihypertensives or certain calcium channel blockers.

Side effects and interactions: Common adverse effects include bradycardia, fatigue, dizziness, and hypotension. Less frequent effects include sexual dysfunction and cold extremities. Potential drug interactions exist with other antihypertensives, calcium channel blockers, and agents affecting glucose metabolism. Pregnancy category C; lactation should be considered with caution.