Complex sentence: While having almost no psychoactive effects at medically-recommended doses, dextromethorphan has euphoric, psychedelic, and dissociative properties when administered in doses well above those which are considered therapeutic medically for cough suppression.
Split into simpler sentences: While having almost no psychoactive effects at medically-recommended doses. Dextromethorphan has euphoric, psychedelic, and dissociative properties when administered in doses well above those which are considered therapeutic medically for cough suppression.