Table 1 .

List of medications used by study participants (morphine conversion factor) [23, 24]

Natural opium alkaloids   • Codeine phosphate hemihydrate (0.15)   • Morphine sulfate pentahydrate (1.00)   • Morphine hydrochloride trihydrate (1.00)   • Oxycodone hydrochloride (1.50)   • Hydromorphone hydrochloride (4.00)   • Oxycodone hydrochloride + naloxone hydrochloride (1.50) Diphenylpropylamine derivatives   • Methadone hydrochloride (3.00) Phenylpiperidine derivatives   • Fentanyl (7.20) Oripavine derivatives   • Buprenorphine (12.60) Opioids in combination with non-opioid analgesics   • Paracetamol + codeine phosphate hemihydrate (0.15) Other opioids   • Tramadol hydrochloride (0.10)   • Tapentadol (0.40)