Abstract
Opioid analgesics such as morphine and fentanyl have been widely used for the treatment of cancer pain. The PK/PD for these opioids was mainly estimated in intraoperative plasma concentration and putative effect-site concentration by multi-compartment models including effect-site compartment. However, the PK/PD for the widely used opioid oxycodone has rarely been estimated. Leow et al measured both the plasma concentration of oxycodone and VAS after intravenous administration in cancer patient. Here, based on their report, we simulated the PK/PD for oxycodone and compared it with those for morphine and fentanyl.
After 5 min intravenous injection of opioid, the tmax of oxycodone was 14 min. With regard to the tmax of those opioids, morphine was 112 min, morphine-6-gluclonized metabolite was 352 min, and fentanyl was 2 min. Under the same conditions, time above 50% maximum concentration of the putative effect site concentration was 60 min in oxycodone. Regarding those of other opioids, morphine was 441 min, morphine-6-gluclonized metabolite was 997 min, and fentanyl was 22 min. As a result, after intravenous administration of a single dose of opioids, the rank order of pain relief duration time length was the following: morphine > oxycodone > fentanyl and that of pain relief onset time rapidity was the following: fentanyl > oxycodone > morphine. These simulations were thought to be useful information for planning how much opioid analgesic should be intravenously administered.
