Pattern and probability of dispensing of prescription opioids and benzodiazepines among the new users in Australia: a retrospective cohort study

Objective Opioids and benzodiazepines are recommended to use for a short duration. Clinicians face a challenge to appraise the risk of new users to become long-term users. This study examined the pattern and probability of opioids and benzodiazepines dispensing among the new users. Design A unit-record data of an incident and a point-incident cohort of new users, who were not dispensed in the previous 2 years, was examined and retrospectively followed up for 24 months. Setting Australia. Participants A random 10% national sample. Primary and secondary outcome measures Distribution of total dispensing in calendar months. Probability of staying in the cohort in each successive month. Effect of first month's dispensing pattern on the total duration of dispensing during 2nd-24th month in total number of calendar months the dispensing was recorded. Results In the incident cohort, 68.24% were dispensed opioids, 23.96% were dispensed benzodiazepines and 7.80% were dispensed both medicines. Over 70% in the incident cohort and 50% in the point-incident cohort were dispensed for a month only. Codeine was the most prevalent opioid, dispensed to 52% of opioid users; and diazepam was the most prevalent benzodiazepines, dispensed to 45.34% of benzodiazepine users. The probability of staying in the cohort and hence receiving further dispensing continued to be very high if dispensing did not end in the first month. The quantity (in defined daily dose) and the total number of dispensing episodes in the first month were significant predictors of the total duration of dispensing in the later period. Conclusions Since harms from long-term use of these medicines may outweigh the benefits, and since the probability of further dispensing was high for those who were dispensed for more than a month, clinicians should endeavour to keep the dispensing duration and quantity as small as possible while initiating a prescription for the new users.