"Among persons aged 12 or older in 2010-2011 who used pain relievers nonmedically in the past year and indicated that they most recently obtained the drugs from a friend or relative for free in the past year, 81.6 percent of the friends or relatives obtained the drugs from just one doctor (Figure 2.14). About 1 in 20 of these past year nonmedical users of pain relievers (5.5 percent) reported that the friend or relative got the pain relievers from another friend or relative for free, 3.9 percent reported that the friend or relative bought the drugs from a friend or relative, 1.9 percent reported that the friend or relative bought the drugs from a drug dealer or other stranger, and 1.8 percent reported that the friend or relative took the drugs from another friend or relative without asking."

Source

Substance Abuse and Mental Health Services Administration, Results from the 2011 National
Survey on Drug Use and Health: Summary of National Findings, NSDUH Series H-44, HHS Publication No. (SMA) 12-4713. Rockville, MD: Substance Abuse and Mental Health Services Administration, 2012, p. 28.
http://www.samhsa.gov/data/NS…