Vasopressors & Inotropes Practice Test

Enantioselective metabolism can create metabolites with distinct receptor actions, and here the effect hinges on which enantiomer shapes the active metabolite. Blocking alpha-1 receptors removes the usual vasoconstrictive signal, causing vasodilation. The positive enantiomer, due to its specific three-dimensional arrangement, is the one that metabolizes into an active alpha-1 antagonist metabolite, so it drives the vasodilatory effect. The negative enantiomer either doesn’t form that same active metabolite or forms one with little or no alpha-1 antagonism, so it doesn’t produce the same vasodilation. That stereochemical fit explains why the active metabolite comes from the positive enantiomer.