Dextromethorphan (CRM)

Dextromethorphan (DXM) is a dextratrorotatory morphinan with structural similarity to levorphanol, codeine, and morphine. Because of its strong antitussive effects, dextromethorphan is widely used as a cough suppressant.1 However, it does not provoke opioid activity as is characteristic of several other morphine derivatives. DXM binds to and inhibits NMDA (IC50 = 0.55 μM) and nicotinic receptors (IC50s = 0.7-3.9 μM) and blocks receptor-gated and voltage-gated calcium channels (IC50 = 60 μM) and voltage-gated sodium channels (IC50 = 78 μM).1,2,3 DXM has been used in multimodal analgesic therapies for acute and neuropathic pain.1,4

References
1. Weinbroum, A.A., Rudick, V., Paret, G., et al. The role of dextromethorphan in pain control. Can.J.Anesth. 47(6), 585-596 (2000).
2. Damaj, M.I., Flood, P., Ho, K.K., et al. Effect of dextrometorphan and dextrorphan on nicotine and neuronal nicotinic receptors: In vitro and in vivo selectivity. Journal of Pharmacology and Experimental Therapeutics 312(2), 780-785 (2005).
3. Netzer, R., Pflimlin, P., and Trube, G. Dextromethorphan blocks N-methyl-D-aspartate-induced currents and voltage-operated inward currents in cultured cortical neurons. European Journal of Pharmacology 238, 209-216 (1993).
4. Chen, Y.W., Chu, K.S., Lin, C.N., et al. Dextromethorphan or dextrorphan have a local anesthetic effect on infiltrative cutaneous analgesia in rats. Anesthesia and Analgesia 104(5), 1251-1255 (2007).