Levomethorphan is the l-stereoisomer of methorphan. The effects of the two isomers are quite different. Dextromethorphan is an antitussive at low doses and a dissociative at much higher doses whereas levomethorphan is an opioid analgesic. Levomethorphan has effects similar to levorphanol but is less potent as it must be demethylated to the active form by liver enzymes before becoming active.
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