Which medication is characterized as a pure α-adrenergic vasoconstrictor?

Phenylephrine is recognized as a pure α-adrenergic vasoconstrictor. It specifically stimulates the alpha-adrenergic receptors, leading to vasoconstriction, which effectively increases systemic vascular resistance and can elevate blood pressure in patients with hypotension. This makes it particularly useful in clinical settings where vasoconstriction is needed without the additional β-adrenergic effects found in other medications.

Dopamine, while it can have vasoconstrictive properties at higher doses, also has dopaminergic and β-adrenergic effects, which makes it not a pure α-agonist. Norepinephrine and epinephrine, on the other hand, are both catecholamines that can activate α-adrenergic receptors but also significantly stimulate β-adrenergic receptors as well, leading to increased heart rate and cardiac contractility, thereby complicating their effects compared to phenylephrine. This distinction is critical in the application of these medications in managing different clinical scenarios.