The Ontario Drug Benefit database was used to ascertain opioid use after hospital discharge. These opioids included codeine, morphine, oxycodone, hydromorphone, meperidine, oxymorphone, methadone, and transdermal fentanyl. We also characterised these drugs by whether they were sustained release formulations. Early post-discharge opioid use was defined as one or more prescriptions for opioids within 1 to 90 days after surgery. Prolonged opioid use after hospital discharge was defined as one or more opioid prescriptions within 1 to 90 days after surgery along with one or more prescriptions for opioids within 91 to 180 days after surgery. This 90 day minimum interval for defining prolonged opioid use is more conservative than the 60 day interval used by the International Association for the Study of Pain to define persistent postsurgical pain,17 which has been criticised as being too short.18 (link)