The term ‘polydrug use’ is used to describe the use of more than one drug or type of drug by an individual either at the same time or sequentially. It encompasses use of both illicit drugs and legal substances, such as alcohol and medicines.
Among polydrug users, a broad distinction can be made between socially marginalised users of heroin and a range of other substances — such as cocaine, benzodiazepines and alcohol — and socially integrated people using combinations such as cocaine and alcohol or cannabis and alcohol problematically.
The use of multiple drugs potentially increases risks and worsens dependence. The most severe consequences of polydrug use include fatal and non-fatal overdoses, hepatotoxicity and compromised treatment outcomes.
- Information is limited on current treatment practices in Europe in managing polydrug use.
- While it is assumed that polydrug use is hard to treat, large outcome studies in Europe show that treatment significantly reduces multiple drug use among highly problematic users.
Summary of the available evidence
The evidence base in this area is not well-developed as most studies focus on specific substances. However, some pointers can be gleaned from a few studies:
- Prevention: Some prevention approaches to address misuse of medicines have been found to reduce polydrug use involving the misuse of medicines. Also, effective prevention approaches (such as those highlighted in the briefings on festival and nightlife settings, schools and colleges, and vulnerable young people), as these are not usually substance-specific, should help reduce polydrug use.
- Treatment: Large national treatment outcomes studies in Australia, Italy and the United Kingdom show that drug treatment substantially reduces the proportion of clients who use multiple substances. These findings are supported by systematic reviews of a small number of randomised controlled studies that have demonstrated that pharmacological and psychosocial interventions, such as contingency management, can reduce polydrug use (moderate quality of evidence).
- Harm-reduction services for problematic drug users usually address the harms and risk behaviours for injecting rather than focusing on a specific substance. These interventions combined with other types of services such as outreach work and OST may improve the health of polydrug users.
Implications for policy and practice
- Polydrug use increases the risk of a wide range of drug-related harms. Among the most severe consequences, the concomitant use of several depressant drugs such as opioids, benzodiazepines and alcohol increases the risk of fatal and non-fatal overdose.
- The management of polydrug use remains a complex and challenging task. Treatment is often less successful for individuals who use multiple substances.
- Psychosocial interventions can contribute to reducing polydrug use among treatment clients, especially stimulant use among clients in opioid substitution treatment.
- The reduction of polydrug use should be a priority within harm reduction interventions.
- Given the impact of polydrug use on overdose risk, information on general dangers and specific risky combinations needs to be provided for opioid users and included in counselling interventions for this group.
- There is a need to develop a clearer picture of the extent and nature of polydrug use among different drug user groups to support the development of appropriate responses.