Which opioid is unique in having both local anesthetic and narcotic properties?

Which opioid is unique in having both local anesthetic and narcotic properties?

• A. Morphine
• B. Nalbuphine
• C. Hydrocodone
• D. Meperidine

Answer: (D)

Meperidine is unique because, in addition to its opioid (narcotic) analgesic action, it can block voltage-gated sodium channels in nerve membranes, giving it a mild local anesthetic effect. This sodium channel blockade is the mechanism by which classic local anesthetics work, so meperidine stands out among common opioids for having this secondary property. The other opioids listed provide analgesia primarily through receptor activation (mu or kappa) and do not have clinically meaningful sodium channel–blocking, local anesthetic effects. Thus they lack that added local anesthetic property. While the local anesthetic effect of meperidine is modest, its use is limited by other risks (like potential neurotoxicity from its metabolite normeperidine), which is why it’s not typically used as a local anesthetic agent.

Meperidine is unique because, in addition to its opioid (narcotic) analgesic action, it can block voltage-gated sodium channels in nerve membranes, giving it a mild local anesthetic effect. This sodium channel blockade is the mechanism by which classic local anesthetics work, so meperidine stands out among common opioids for having this secondary property.

The other opioids listed provide analgesia primarily through receptor activation (mu or kappa) and do not have clinically meaningful sodium channel–blocking, local anesthetic effects. Thus they lack that added local anesthetic property. While the local anesthetic effect of meperidine is modest, its use is limited by other risks (like potential neurotoxicity from its metabolite normeperidine), which is why it’s not typically used as a local anesthetic agent.