"• Past year nonmedical users of psychotherapeutic drugs are asked how they obtained the drugs they most recently used nonmedically. Rates averaged across 2011 and 2012 show that more than one half of the nonmedical users of pain relievers, tranquilizers, stimulants, and sedatives aged 12 or older got the prescription drugs they most recently used 'from a friend or relative for free.' About 4 in 5 of these nonmedical users who obtained prescription drugs from a friend or relative for free indicated that their friend or relative had obtained the drugs from one doctor."

Source

Substance Abuse and Mental Health Services Administration, Results from the 2012 National Survey on Drug Use and Health: Summary of National Findings, NSDUH Series H-46, HHS Publication No. (SMA) 13-4795. Rockville, MD: Substance Abuse and Mental Health Services Administration, 2013, p. 29.
http://www.samhsa.gov/data/NS…
http://www.samhsa.gov/data/NS…