Which of the following local anesthetics has the highest lipophilicity and is most likely to cause systemic toxicity when absorbed rapidly?

Explanation

## Local Anesthetic Lipophilicity and Toxicity Risk **Key Point:** Lipophilicity directly correlates with systemic toxicity risk. Highly lipophilic agents penetrate nerve sheaths and cell membranes more readily, leading to rapid CNS and cardiac toxicity. ### Lipophilicity Ranking (High to Low) | Local Anesthetic | Lipophilicity | Systemic Toxicity Risk | Potency | | --- | --- | --- | --- | | Bupivacaine | Very High | **Highest** | High | | Etidocaine | Very High | Very High | High | | Prilocaine | Moderate | Moderate | Moderate | | Lidocaine | Low-Moderate | Moderate | Moderate | | Procaine | Low | Low | Low | **High-Yield:** Bupivacaine's high lipophilicity makes it: - Rapidly absorbed into CNS → seizures, loss of consciousness - Rapidly absorbed into myocardium → arrhythmias, cardiac arrest (notoriously difficult to resuscitate) - More potent and longer-acting, but with greater toxicity potential **Clinical Pearl:** Bupivacaine-induced cardiac toxicity is particularly refractory to standard ACLS. Lipid emulsion therapy (Intralipid®) is the antidote for severe bupivacaine toxicity, not for other local anesthetics. **Warning:** Do NOT confuse potency with safety. Bupivacaine is more potent (lower dose needed) but MORE toxic systemically than lidocaine.