Polydrug use poses significant risks and is more common among people with drug use disorders.

• No consensus definition of polydrug use currently exists but it can be generally understood as taking two or more drugs together or in sequence (intentionally or unintentionally), with both forms increasing the risk of harmful interactions and fatal and non-fatal overdoses.
• Intentional polydrug use is more common among people with drug use disorders and carries significant acute and chronic risks, while unintentional (inadvertent) use often results from drug adulteration.
• While relatively uncommon in the general population (median prevalence of 2.4 per cent in reporting countries), polydrug use is more common among people with drug use disorders and generally increases with the level of intensity of drug use.
• The combinations of drugs that are used by individuals can include many psychoactive substances and vary across regions.