Metoprolol

Metoprolol is a cardioselective beta-1 adrenergic receptor blocker. At therapeutic doses, it preferentially blocks beta-1 receptors in the heart rather than beta-2 receptors in the lungs and peripheral vasculature, making it safer than non-selective beta blockers in patients with mild respiratory conditions. By blocking the effects of catecholamines (adrenaline/epinephrine) on the heart, metoprolol reduces heart rate, reduces myocardial contractility, and lowers blood pressure.¹

Two salt forms are available with different pharmacokinetic profiles: metoprolol tartrate (immediate-release, Lopressor) requires twice-daily dosing; metoprolol succinate (extended-release, Toprol-XL) is formulated for once-daily dosing with more stable plasma levels.

Metoprolol tartrate (Lopressor):

• Hypertension
• Angina pectoris
• Acute myocardial infarction (to reduce cardiovascular mortality)¹

Metoprolol succinate (Toprol-XL):

• Hypertension
• Angina pectoris
• Stable symptomatic heart failure (NYHA class II or III) of ischemic, hypertensive, or cardiomyopathic origin¹

For hypertension: 25–100 mg once daily (succinate) or 100–450 mg per day in divided doses (tartrate).

For heart failure: Start at 12.5–25 mg once daily (succinate only), double every 2 weeks as tolerated to target of 200 mg once daily.¹

Oral tablets. Extended-release tablets should be swallowed whole, not crushed or chewed.

Store at controlled room temperature, away from moisture and heat.¹

Critical warning — do not stop abruptly: Abrupt discontinuation of metoprolol in patients with coronary artery disease has been associated with severe angina exacerbation, myocardial infarction, and ventricular arrhythmias. Always taper the dose gradually when discontinuing.¹

Additional considerations:

• Fatigue and exercise intolerance: Beta blockers reduce maximum heart rate response to exercise, which can cause fatigue and reduced exercise capacity — a common reason for dose adjustment in active patients.
• Masking hypoglycemia: Metoprolol can mask the tachycardia (racing heart) that alerts diabetic patients to hypoglycemia, though sweating is usually preserved. Use with caution in patients with diabetes on insulin or sulfonylureas.
• Bradycardia: Can cause excessively slow heart rate, particularly at higher doses or in combination with other rate-slowing medications (calcium channel blockers like verapamil or diltiazem, digoxin).
• Bronchospasm: Although cardioselective, metoprolol may worsen bronchospasm in patients with severe reactive airway disease at higher doses.
• CYP2D6 interactions: Metoprolol is primarily metabolized by CYP2D6. Potent CYP2D6 inhibitors (fluoxetine, paroxetine, bupropion, quinidine) can significantly increase metoprolol exposure and enhance its effects.
• Heart failure: Starting doses must be very low in heart failure patients; rapid uptitration can worsen decompensation.