Methorphan comes in two isomeric forms, each with differing pharmacology and effects: * Dextromethorphan - An over-the-counter cough suppressant, as well as dissociative hallucinogen. * Levomethorphan - A potent opioid analgesic that was never clinically developed; a prodrug of the powerful opioid agonist analgesic levorphanol (Levo-Dromoran).