Patterns of opiod use in patients with cancer and non-cancer pain and its relevant clinical outcomes in non-cancer pain

Abstract

Opioids are the gold standard for the treatment of moderate to severe acute pain and cancer pain. However, opioids are increasingly prescribed to treat non-cancer pain for long-term which has become a public health concern due to increasing evidences of opioid-related harms such as abuse, misuse, and opioid overdose-related deaths associated with long-term opioid therapy. Little is known about the patterns of opioid prescribing among non-cancer pain patients and the characteristics of those on long-term opioid therapy in Malaysia. Information is also lacking on the risks of opioid abuse/misuse among non-cancer pain patients receiving opioid treatment for their pain. This study therefore investigated individual patient level opioid prescribing patterns and the differential patterns of opioid persistence between cancer pain and non-cancer pain patients at Malaysian outpatient tertiary hospital settings over 3 follow-up years (part 1). This study also investigated the clinical outcomes and risks of opioid abuse/misuse in non-cancer patients attending pain clinics (part 2). For part 2, non-cancer patients were stratified into short-term and long-term opioid user groups. The clinical outcomes were assessed using the Brief Pain Inventory – Short Form (BPI-SF), the Medication Quantification Scale – III (MQS-III), the Short Form-36v2 (SF-36v2) Health Survey and assessed for opioid adverse effects. The risk of opioid abuse/misuse were assessed using the Screener and Opioid Assessment for Patients with Pain - Revised (SOAPP-R). Factors influencing long-term opioid use and high risk of abuse/misuse were also analysed using multivariable logistic regression. Opioids included in this study were dihydrocodeine, oxycodone, morphine, fentanyl, and buprenorphine. In the first part of the study, a total of 922 patients with a mean age of 60 (±15.4) years who received opioids were identified. A comparative analysis indicated that compared to cancer pain patients (n = 665), non-cancer pain (n = 257) patients were prescribed relatively lower doses of opioids of <100 mg/day and for longer periods of at least 60 days of opioid days’ supply on average in a follow-up year. The differential persistence patterns of opioid use over time revealed a pattern of tapering off opioid treatment among persistent opioid users in the non-cancer pain group in contrast to the cancer pain group. In the second part, a total of 61 non-cancer pain patients were recruited where no significant differences in the clinical outcomes were found between the short-term (n=30/61) and long-term opioid users (n=31/61). Notably, 62.3% of these non-cancer pain patients were found to be at high risk of opioid abuse/misuse. Predictors of high risk of abuse/misuse included younger age (OR 0.90, 95% CI 0.86, 0.98) and higher pain interference (OR 2.17, 95% CI 1.14 – 4.13). These findings suggest that opioid prescribing practices for non-cancer pain at outpatient tertiary hospital settings in Malaysia is in accordance with opioid prescribing guidelines which recommend against high dose opioid therapy and encouraging tapering off opioid treatment. Nonetheless, the high proportion of non-cancer pain patients attending pain clinics at high risk of opioid abuse/misuse is worrisome which calls for further investigation into the risks of opioid abuse/misuse among non-cancer pain patients attending pain clinics.