Compared to 1:200,000 epinephrine, which statement about epinephrine concentrations in local anesthetics is true?

• A. 1:100,000 contains more epinephrine per volume and provides greater vasoconstriction and longer duration than 1:200,000.
• B. 1:100,000 contains less epinephrine per volume than 1:200,000.
• C. Both concentrations provide the same vasoconstriction and duration.
• D. 1:200,000 provides greater vasoconstriction and longer duration.

Answer: (A)

The amount of epinephrine per unit volume determines how strongly the local anesthetic will constrict blood vessels and how long the numbness lasts. A higher concentration means more epinephrine in each milliliter, which increases vasoconstriction by acting on vascular smooth muscle. This tighter narrowing reduces blood flow to the injection site, limits how quickly the anesthetic is absorbed systemically, and thereby extends the duration of anesthesia. So the formulation with the greater epinephrine concentration provides stronger vasoconstriction and a longer-lasting effect than the more diluted option. The alternatives don’t fit because a lower concentration does not produce more vasoconstriction or a longer duration, and the two concentrations do not produce identical effects.