Final answer:
IV metaraminol is a pharmacologic agent that causes vasoconstriction by acting on alpha-1 adrenergic receptors, leading to an increase in blood pressure.
Step-by-step explanation:
The pharmacologic effect of IV metaraminol, which is an alpha-1 agonist drug, is vasoconstriction. Metaraminol acts on alpha-1 adrenergic receptors located on the vascular smooth muscle, causing them to contract. This leads to narrowing of the blood vessels and an increase in blood pressure. It is different from drugs like dopamine and isoproterenol, which mimic the effects of epinephrine and norepinephrine (NE) and can lead to vasodilation and increased heart rate (positive inotropic effects) due to stimulation of beta-1 receptors. On the other hand, medications such as beta blockers inhibit these effects by blocking beta receptors, thus lowering heart rate and potentially leading to decreased cardiac output if overprescribed.