Objective: Concurrent use of opioids and benzodiazepines may cause a range of adverse health outcomes including fatal overdose. However, little is known about levels of concurrent use and its variation across jurisdictions. This study examined the population-level prevalence of concurrent use in Australia. Methods: We analyzed a 10% sample of unit record data of prescription opioids and benzodiazepines dispensed between January 2013 and December 2016. Using dispensing dates and days of supply in terms of defined daily dose (DDD), the concurrent users were identified as those for whom the supply in DDD quantity for one medicine overlapped with the supply day of the other. Multivariable and multilevel regression models were developed. Results: During the 4 years, almost a million (12.41% of 7.96 million) individuals were identified as concurrent users. Significantly more women were concurrent users than men across all age groups. On average, 1,750 per 100,000 people were concurrent users per year. There was substantial variation in the yearly average of concurrent users across jurisdictions, ranging from less than 1 to 5,400 per 100,000 people (standardized). Much of this variation was attributed to individual-level circumstances rather than structural factors. Conclusion: Concurrent use of opioid and benzodiazepine was common in Australia. There was considerable variation across jurisdictions in terms of the number of concurrent users. Women, older people, or those living in socioeconomically disadvantaged areas were dominant groups of concurrent users. Further research is needed to examine the precise reasons for concurrent use.
Association between concurrent use of prescription opioids and benzodiazepines and overdose: retrospective analysis