The vasoconstrictor frequently added to local anesthetics to prolong effect is which agent?

• A. Norepinephrine
• B. Epinephrine (adrenaline)
• C. Dopamine
• D. Phenylephrine

Answer: (B)

Vasoconstrictors added to local anesthetics work by narrowing the blood vessels at the injection site, which slows the removal of the anesthetic into the bloodstream. This keeps more drug at the nerve target for a longer period and reduces systemic toxicity, while also helping control bleeding.

Epinephrine (adrenaline) is the standard choice for this purpose because it reliably constricts vessels when injected locally by acting on alpha-adrenergic receptors. That vasoconstriction prolongs the anesthetic effect and provides better local hemostasis. Other agents can cause vasoconstriction as well, but they’re not used as routinely due to less favorable safety or pharmacologic profiles in this context.