The challenge of complex drug use: Associated use of codeine-containing medicines and new psychoactive substances in a European cross-sectional online population.

Amongst NPS users, codeine is less likely to be used daily but more likely to be used for recreational purposes. Smaller populations engaging in high-risk use exist who take multiple drugs in high doses. Combinations of misused codeine and NPS highlight the need for policy to respond to a more complex drug situation.