Metoprolol

Metoprolol is a beta₁-selective adrenergic blocker that slows heart rate and reduces cardiac workload. It is used for hypertension, angina, heart failure, and certain arrhythmias.

Beta-1 adrenergic receptor: A G protein-coupled receptor activated chiefly by epinephrine and norepinephrine, especially in the heart. Metoprolol preferentially blocks this receptor, reducing heart rate and cardiac contractility.
Hypertension: Persistently elevated arterial blood pressure that increases the risk of cardiovascular and kidney disease. Metoprolol lowers blood pressure, though it is not generally a first-choice drug for uncomplicated hypertension.
Atenolol: A hydrophilic beta₁-selective blocker used for hypertension and other cardiovascular conditions. Like metoprolol, atenolol targets beta₁ receptors, but it is eliminated largely unchanged by the kidneys.
Sympathetic nervous system: A branch of the autonomic nervous system that mobilizes the body during stress and activity. Metoprolol dampens some cardiovascular effects of this system's signaling.
Catecholamine: A class of signaling molecules that includes epinephrine, norepinephrine, and dopamine. Epinephrine and norepinephrine activate the receptors that metoprolol blocks.
Angina pectoris: Chest discomfort caused by temporary inadequate blood flow to the heart muscle. By reducing cardiac workload and oxygen demand, metoprolol can prevent angina episodes.
Carvedilol: A beta blocker that also blocks alpha₁ receptors and is used in heart failure and hypertension. Its additional alpha₁ blockade contrasts with metoprolol's predominant beta₁ selectivity.
First-pass metabolism: Drug metabolism in the gut wall and liver before an orally taken dose reaches systemic circulation. Extensive first-pass metabolism contributes to variation in metoprolol exposure between people.
Cardiac output: The volume of blood the heart pumps per minute. Metoprolol can lower cardiac output by slowing the heart and reducing contraction strength.
Heart failure: A clinical syndrome in which the heart cannot meet the body's needs without elevated filling pressures. Extended-release metoprolol succinate is one of the beta blockers shown to improve outcomes in stable systolic heart failure.

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