Both, but for different reasons: The "overdoses" from prescription opiates are often acetaminophen vs. the opiate (no direct sources w/ numbers, but example: ht

Both, but for different reasons: The "overdoses" from prescription opiates are often acetaminophen vs. the opiate (no direct sources w/ numbers, but example: http://www.medscape.com/viewarticle/820039 http://www.medscape.com/viewarticle/820039). Whereas with illegal opiates it's often from a difference in purity from one purchase to the next. This is where a regulated drug market would alleviate that issue 100%.