Complications Adverse reaction to the anesthetic or delivery vehicle (eg, allergic reaction to the anesthetic [rare] or to methylparaben [a preservative]) Toxicity due to anesthetic overdose (eg, seizure, cardiac arrhythmias) or sympathomimetic effects due to epinephrine (if using an anesthetic - epinephrine mixture) Intravascular injection of anesthetic or epinephrine Hematoma Neuritis Spread of infection, by passing the needle through an infected area Most complications result from inaccurate needle placement.