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Though Freud and a number of American physicians reported some initial successes in treating morphine addicts with cocaine,* a fellow physician named Adolf Albrecht Erlenmeyer warned that cocaine was itself addictive and described it as the "third scourge of mankind"—after morphine and alcohol.
Freud soon realized to his chagrin that Erlenmeyer was correct. Freud's friend and patient, Ernst von Fleischl-Marxow, became the first morphine addict in Europe to be cured by using cocaine; he was also one of the first to become dependent on the new drug. This unhappy development dampened Freud's interest in cocaine and helped turn his attention to the psychological theories that eventually won him fame.
Freud's studies of cocaine are still considered basic to modern psychopharmacology. But they did not lead to the discovery of the most effective clinical use of the drug. In an ironic twist, Freud abandoned his interest in cocaine just after he suggested that a colleague, Karl ("Coca") Roller, begin experimenting with its use in easing the pain of eye surgery. So it was Koller and not Freud who invented local anesthesia.
* Cocaine, which could be obtained legally, was widely used at the time. Sir Arthur Conan Doyle's fictional detective, Sherlock Holmes, who injects a "seven-per-cent solution" at the opening of The Sign of the Four, was supposedly a cocaine freak. A new book appropriately titled The Seven-Per-Cent Solution even has Holmes lured to Vienna, where Freud helps him kick the habit.