What effect does the addition of epinephrine to a local anesthetic have?

The addition of epinephrine to a local anesthetic is primarily known for prolonging the duration of anesthesia. Epinephrine is a vasoconstrictor, which means that when it is mixed with a local anesthetic, it constricts blood vessels in the area where the anesthetic is administered. This vasoconstriction reduces the rate of absorption of the anesthetic into the bloodstream.

By slowing down systemic absorption, the anesthetic remains in the target area for a longer period, thus extending the duration of its effect. This is particularly useful in surgical and procedural settings where prolonged anesthesia is required, allowing for longer procedures without the need for additional local anesthetic injections.

Additionally, the lower systemic absorption also contributes to decreased systemic toxicity, but the primary and most noted effect in this context is the prolongation of the duration of anesthesia.