Changes in opioid and other analgesic prescribing following voluntary and mandatory prescription drug monitoring program implementation: A time series analysis of early outcomes

Background: Australian prescription drug monitoring programs (PDMPs) provide information about a patient's recent medication history for controlled drugs at the point of prescribing and dispensing. Despite their increasing use, the evidence for PDMPs is mixed, and is almost exclusively from the United States. This study examined the impact of PDMP implementation on opioid prescribing among general practitioners in Victoria, Australia. Method: We examined data on analgesic prescribing using electronic records of 464 medical practices in the Australian state of Victoria between 01/04/2017 and 31/12/ 2020. We used interrupted time series analyses, to examine immediate and longer-term trends in medication prescribing following voluntary (from April 2019) and mandatory PDMP implementation (from April 2020). We examined changes in three outcomes (i) 'high' opioid dose (50-100mg oral morphine equivalent daily dose (OMEDD) and over 100mg (OMEDD) prescribing (ii) prescribing of high-risk medication combinations (opioids with either benzodiazepines or pregabalin), and (iii) initiation of non-controlled pain medications (tricyclic antidepressants, pregabalin and tramadol).Results: We found no effect of voluntary or mandatory PDMP implementation on 'high-dose' opioid prescribing with reductions only seen in those prescribed < 20mg OMEDD (i.e., the lowest dose category). Co-prescribing of opioids with benzodiazepines (additional 11.87 [95%CI 2.04 to 21.67] patients/10,000 and pregabalin (addi-tional 3.54 [95% CI 0.82 to 6.26] patients/10,000 increased following mandatory PDMP implementation among those prescribed opioids. In contrast to trends of reduced initiation prior to PDMP implementation, we found increased new initiation of non-monitored medications following PDMP implementation (e.g., an immediate increase of 2.32 [95%CI 0.02 to 4.54], patients/10,000 received pregabalin and 3.06 [95%CI 0.54 to 5.5] pa-tients/10,000 received tricyclic antidepressants after mandatory PDMP implementation), and increased tramadol initiation during the voluntary PDMP period (an increase of 11.26 [95%CI: 5.84, 16.67] patients /10,000).Conclusion: PDMP implementation did not appear to reduce prescribing of high opioid doses or high-risk combi-nations. Increased initiation of tricyclic antidepressants, pregabalin and tramadol may indicate a possible unin-tended effect.