The four-year-old elephant, known as Big Brother, was illegally captured in 2005 in southwest China by the smugglers, who fed him with bananas laced with heroin to keep him under control.
Several months later police arrested the smugglers and freed the elephant, but after monitoring Big Brother noticed repeated signs of distress.
Medics confirmed that the elephant was suffering from drug withdrawal symptoms, and sent it for a three-year detox program in a wild animal protection center in the Hainan province.
The elephant received methadone injections at five times the maximum human dosage. After a year of treatment, the dose was gradually reduced, and the animal recovered from his addiction, the agency said.
The elephant is expected to arrive at a wildlife park in Kunming, the capital of southwest China's Yunnan province, on Saturday along with three other elephants that had been held by the smugglers.
Reported by RIA Novosti