| 1. Level of consciousness at the time of opioid administration |
| 2. Ability of patients to perceive the opioid effects |
| 3. Influence of other concurrently administered drugs e.g. hypnotic and sedative agents |
| 4. Severity of the pain experienced at the time of opioid administration |
| 5. Ability of patients to directly or indirectly control their opioid use |
| 6. Patients’ discretion in determining the use of opioids provided |
| 7. Whether the drugs are administered directly by the providers or are consumed by the patients |
| 8. Level of patient monitoring |
| 9. Surveillance of patients’ opioid use |
| 10. Period of opioid administration-varying from minutes to months in the perioperative period |
| 11. Expected duration of pain-varying from days to months in the perioperative period |
| 12. Type, route and potency of the opioids administered e.g. ultra short-acting intravenous vs. |
| 13. Extended release oral preparations |
| 14. Heterogeneity of prescribers e.g. anesthesiologists vs. a range of surgeons, primary care providers, pain specialists, and internists |
| 15. Prescribers’ background, experience and knowledge of prescribing opioids |
