Which local anesthetic is NOT commonly combined with epinephrine formulations in the US?

Bupivacaine is not commonly combined with epinephrine formulations in the United States primarily due to its potency and longer duration of action. While it is a frequently used local anesthetic, especially in procedures that require prolonged analgesia, the addition of epinephrine does not significantly enhance its efficacy. Moreover, bupivacaine has a higher risk of systemic toxicity, which can be exacerbated by the vasoconstrictive properties of epinephrine.

In contrast, mepivacaine, prilocaine, and lidocaine are often combined with epinephrine to prolong their effects and to reduce systemic absorption by causing vasoconstriction at the injection site. This helps to improve the duration of anesthesia and minimizes bleeding during procedures. However, bupivacaine's characteristics make it less suited for such combinations, contributing to its distinct usage patterns in clinical settings.