Pharmacokinetics of oxycodone hydrochloride and three of its metabolites after intravenous administration in Chinese patients with pain

Exploring the impact of CYP2D6 and UGT2B7 gene-drug interactions, and CYP-mediated DDI on oxycodone and oxymorphone pharmacokinetics using physiologically-based pharmacokinetic modeling and simulation

Oxycodone is one of the most commonly used opioids to treat moderate to severe pain. It is metabolized mainly by CYP3A4 and CYP2D6, while only a small fraction of the dose is excreted unchanged into the urine. Oxymorphone, the metabolite primarily formed by CYP2D6, has a 40- to 60-fold higher mu-opioid receptor affinity than the parent compound. While CYP2D6-mediated gene-drug-interactions (GDIs) and drug-drug interactions (DDIs) are well-studied, they only account for a portion of the variability in oxycodone and oxymorphone exposure. The combined impact of CYP2D6-mediated GDIs and DDIs, CYP3A4-mediated DDIs, and UGT2B7 GDIs is not fully understood yet and hard to study in head-to-head clinical trials given the relatively large number of scenarios. Instead, we propose the use of a physiologically-based pharmacokinetic model that integrates available information on oxycodone's metabolism to characterize and predict the impact of DDIs and GDIs on the exposure of oxycodone and its major, pharmacologically-active metabolite oxymorphone. To this end, we first developed and verified a PBPK model for oxycodone and its metabolites using published clinical data. The verified model was then applied to determine the dose-exposure relationship of oxycodone and oxymorphone stratified by CYP2D6 and UGT2B7 phenotypes respectively, and administered perpetrators of CYP-based drug interactions. Our simulations demonstrate that the combination of CYP2D6 UM and a UGT2B7Y (268) mutation may lead to a 2.3-fold increase in oxymorphone exposure compared to individuals who are phenotyped as CYP2D6 NM / UGT2B7 NM. The extent of oxymorphone exposure increases up to 3.2-fold in individuals concurrently taking CYP3A4 inhibitors, such as ketoconazole. Inhibition of the CYP3A4 pathway results in a relative increase in the partial metabolic clearance of oxycodone to oxymorphone. Oxymorphone is impacted to a higher extent by GDIs and DDIs than oxycodone. We predict oxymorphone exposure to be highest in CYP2D6 UMs/UGT2B7 PMs in the presence of ketoconazole (strong CYP3A4 index inhibitor) and lowest in CYP2D6 PMs/UGT2B7 NMs in the presence of rifampicin (strong CYP3A4 index inducer) covering a 55-fold exposure range.

Opioid analgesic effects on subjective well-being in the operating theatre

Exposure to opioid analgesics due to surgery increases the risk of new persistent opioid use. A mechanistic hypothesis for opioids' abuse liability rests on the belief that, in addition to pain relief, acute opioid treatment improves well-being (e.g. via euphoria) and relieves anxiety. However, opioids do not consistently improve mood in laboratory studies of healthy non-opioid users. This observational study determined how two commonly used opioid analgesics affected patients' subjective well-being in standard clinical practice. Day surgery patients rated how good and how anxious they felt before and after an open-label infusion of remifentanil (n = 159) or oxycodone (n = 110) in the operating theatre before general anaesthesia. One minute after drug injection, patients reported feeling intoxicated (> 6/10 points). Anxiety was reduced after opioids, but this anxiolytic effect was modest (remifentanil Cohen's d = 0.21; oxycodone d = 0.31). There was moderate to strong evidence against a concurrent improvement in well-being (Bayes factors > 6). After remifentanil, ratings of 'feeling good' were significantly reduced from pre-drug ratings (d = 0.28). After oxycodone, one in three participants felt better than pre-drug. Exploratory ordered logistic regressions revealed a link between previous opioid exposure and opioid effects on well-being, as only 14 of the 80 opioid-naïve patients reported feeling better after opioid injection. The odds of improved well-being ratings after opioids were higher in patients with previous opioid exposure and highest in patients with > 2 weeks previous opioid use (adjusted OR = 4.4). These data suggest that opioid-induced improvement of well-being is infrequent in opioid-naïve patients. We speculate that peri-operative exposure could increase risk of persistent use by rendering subsequent positive opioid effects on well-being more likely.

Effective Doses of Nalbuphine Combined With Propofol for Painless Gastroscopy in Adults: A Randomized Controlled Trial

Objective: This prospective study evaluated the 50% effective dose (ED₅₀) and 95% effective dose (ED₉₅) of nalbuphine combined with propofol during painless gastroscopy.

Methods: Seventy-five patients who underwent painless gastroscopy were randomly divided into five groups (group N₀, N_0.05, N_0.1, N_0.15, and N_0.2), with doses of 0, 0.05, 0.1, 0.15, or 0.2 mg/kg nalbuphine in each group. Propofol was given to all groups as the sedative. The bispectral index (BIS) value, propofol dose, examination time, and awakening time were recorded. The number of patients with intolerance indexes (coughing, retching, swallowing, or limb movement) was recorded in each group. The ED₅₀/ED₉₅ of nalbuphine combined with propofol for gastroscopy were calculated.

Results: Compared with those of groups N₀, N_0.05, or N_0.1, the propofol dose and awakening time were significantly reduced in group N_0.15 or N_0.2 (p < 0.05). The successful rate of painless gastroscopy in group N_0.15 or N_0.2 significantly increased compared to that of group N₀ or N_0.05 (p < 0.05). When combined with propofol, nalbuphine had an ED₅₀ and ED₉₅ for painless gastroscopy of 0.078 mg/kg (95% CI, 0.056–0.098 mg/kg) and 0.162 mg/kg (95% CI, 0.134–0.217 mg/kg), respectively.

Conclusion: The ED₅₀/ED₉₅ of nalbuphine combined with propofol are 0.078 and 0.162 mg/kg, respectively, for painless gastroscopy. Nalbuphine at 0.162 mg/kg combined with propofol is effective and safe for painless gastroscopy in adults.

Lower Background Infusion of Oxycodone for Patient-Controlled Intravenous Analgesia, Combined with Ropivacaine Intercostal Nerve Block, in Patients Undergoing Thoracoscopic Lobectomy for Lung Cancer: A Randomized, Double-Blind, Controlled Clinical Trial

Purpose

To compare the efficacy of a lower dose background infusion of oxycodone for patient-controlled intravenous analgesia (PCIA) with the conventional dose, following intercostal nerve block, for the management of postoperative pain in patients undergoing thoracoscopic lobectomy for lung cancer.

Patients and Methods

This was a prospective, single-center, randomized, parallel-group, double-blind, controlled clinical trial. In total, 155 patients scheduled for elective radical lobectomy via video-assisted thoracoscopy were recruited from December 2018 to July 2019, of whom 140 were ultimately included in the study population. Patients were randomized to receive either oxycodone 0.25 mg/h (low-dose group, n=70) or oxycodone 0.5 mg/h (control group, n=70) as a background infusion for PCIA, following ropivacaine intercostal nerve block, for postoperative pain management. The primary endpoints were rest and dynamic visual analogue scale (VAS) scores within 72 h of the operation. The secondary endpoints were patient satisfaction scores, consumption of postoperative analgesics, times of patient-controlled analgesia (PCA), and adverse events.

Results

All 140 enrolled patients completed the study requirements and were included in the final analysis. The rest and dynamic VAS scores at 4 h, 24 h, 48 h, and 72 h postoperative were comparable between the low-dose group and the control group (P>0.05). However, the low-dose group had statistically significantly higher patient satisfaction scores (P<0.001) and lower postoperative analgesic consumption (P<0.001) as well as lower incidence of nausea and vomiting (P<0.05). The times of PCA was not statistically significantly different between the two groups, and no serious adverse events occurred in either group (P>0.05).

Conclusion

A low-dose background infusion of oxycodone for postoperative PCIA can achieve a comparable analgesic effect to the conventional dose after thoracoscopic lobectomy for lung cancer. Furthermore, the low-dose regimen was associated with reduced consumption of oxycodone and increased patient satisfaction.

Evaluation of Recombinant CYP3A4 Variants on the Metabolism of Oxycodone In Vitro

Cytochrome P450 3A4 is a highly polymorphic enzyme and metabolizes approximately 40%-60% of therapeutic drugs. Its genetic polymorphism may significantly affect the expression and function of CYP3A4 resulting in alterations of the pharmacokinetics and pharmacodynamics of the CYP3A4-mediated drugs. The purpose of this study was to evaluate the catalytic activities of 30 CYP3A4 nonsynonymous variants and wild type toward oxycodone in vitro. CYP3A4 proteins were incubated with oxycodone for 30 min at 37 °C and the reaction was terminated by cooling to -80 °C immediately. Ultraperformance liquid chromatography tandem mass-spectrometry was used to analyze noroxycodone, and kinetic parameters Km, Vmax, and intrinsic clearance (Vmax/Km) of noroxycodone were also determined. Compared with CYP3A4.1, 24 CYP3A4 variants (CYP3A4.2-.5, -.7-.16, -.18 and -.19, -.23 and -.24, -.28 and -.29, and -.31-.34) exhibited significantly decreased relative clearance values (from 4.82% ± 0.31% to 80.98% ± 5.08%), whereas CYP3A4.6, -.17, -.20, -.21, -.26, and -.30 displayed no detectable enzyme activity. As the first study of these alleles for oxycodone metabolism in vitro, results of this study may provide insight into establishing the genotype-phenotype relationship for oxycodone and serve as a reference for clinical administrators and advance the provision of personalized precision medicine.

Effect of different doses of intravenous oxycodone and fentanyl on intubation-related hemodynamic responses: A prospective double-blind randomized controlled trial (CONSORT)

BACKGROUND

Intubation using direct laryngoscopy is a risky and painful procedure that is associated with undesirable hemodynamic changes such as tachycardia, hypertension, and arrhythmia. Recently, intravenous oxycodone was introduced and used for the control of acute postoperative pain and to attenuate intubation-related hemodynamic responses (IRHRs), but there is insufficient information regarding its proper dosage. We investigated the attenuating effects of different doses of oxycodone and fentanyl on IRHRs.

METHODS

For calculating oxycodone effective dose (ED95), which attenuated all IRHR changes to less than 20% over baseline values in 95% of male patients at 1 minute after intubation, oxycodone 0.1 mg/kg was injected for the first patient 1 hour before intubation, and the next dose for each subsequent patient was determined by the response of the previous patient using Dixon up-and-down method with an interval of 0.01 mg/kg. After obtaining the predictive oxycodone ED95, 148 patients were randomly allocated to groups receiving normal saline (group C), oxycodone ED95 (group O1), oxycodone 2 × ED95 (group O2), or fentanyl 2 μg/kg (group F). We recorded the incidence of "success" as a less than 20% change from baseline values in all IRHRs 1 minute after intubation.

RESULTS

The predictive oxycodone ED95 was 0.091 (0.081-0.149) mg/kg. The incidence of "success" was highest in group O2 (75.7%), followed by group O1 (62.2%) and group F (45.9%) with significant differences between the groups (P < .001). The systolic, diastolic, mean arterial pressure, and heart rate were not significantly different among groups after administration of either oxycodone or fentanyl. The percentage hemodynamic changes of the group O2 were significantly lower than those of groups F and O1, but the absolute percentage hemodynamic changes were not significantly different among groups F, O1, and O2. The recalculated oxycodone ED95 with probit analysis (0.269 mg/kg) was needed to prevent any arterial pressure and heart rate changes.

CONCLUSIONS

Oxycodone 0.182 mg/kg is more effective in attenuating all IRHRs than fentanyl 2 μg/kg with safe hemodynamic changes. Further research is required to determine if the recalculated oxycodone ED95 (0.269 mg/kg) is also effective and hemodynamically safe for preventing all IRHRs.

Different effects of oxycodone and remifentanil in patients undergoing ultrasound-guided percutaneous radiofrequency ablation of hepatic cancer: a randomized trial

Background

Percutaneous radiofrequency ablation (RFA) is a recently introduced alternative technique for the treatment of hepatic cancer. Anesthesia is required for RFA of hepatic cancer to achieve patient comfort and immobilization during this painful procedure. The purpose of this study was to investigate the analgesic efficacy and evaluate the safety of a single intravenous injection of oxycodone hydrochloride for this procedure.

Patients and methods

A total of 120 American Society of Anesthesiologists class I–II grade patients for elective ultrasound-guided percutaneous RFA were enrolled in this randomized controlled trial. Patients were randomized (1:1) to receive either a single intravenous injection of oxycodone (group O) or continuous infusion of remifentanil (group R). Both groups received the continuous infusion of dexmedetomidine for sedation. Visual analog scale (VAS), rescue analgesic, and side effects were checked during the periprocedural period. In addition, patient and oncologist satisfaction on a scale of 1–5 were determined.

Results

VAS score in group O was significantly lower than in group R at 1, 2, and 3 hours after RFA, and patients in group O required analgesics significantly later and less doses in the first 24 hours after RFA. The occurrence of unwanted body movements was significantly lower in group O. We found no complications including allergic reaction, excessive sedation, and chest wall rigidity in all patients. The patient satisfaction score was significantly higher in group O than that in group R.

Conclusion

Ultrasound-guided percutaneous RFA for hepatic cancer can be completed both with continuous infusion of remifentanil or a single intravenous injection of oxycodone. However, oxycodone hydrochloride provides better patient experience with higher satisfactory score and less unwanted body movements, relieves post-procedural pain better, and is not associated with an increase in adverse effects.

Gender Affects the Median Effective Dose and 95% Effective Dose of Oxycodone for Blunting the Hemodynamic Response to Tracheal Intubation in Narcotic-Naïve Adult Patients

Background

Intravenous (IV) oxycodone has been used at induction to prevent an intubation reaction. The aims of the current study were to calculate the median effective dose (ED₅₀) and the 95% effective dose (ED₉₅) of an IV bolus of oxycodone that blunts the hemodynamic response to tracheal intubation with propofol according to gender and to observe the adverse events of induction-dose oxycodone.

Methods

Adult patients who required general anesthesia and tracheal intubation were enrolled. Tracheal intubation was performed using unified TD-C-IV video laryngoscopy and an ordinary common endotracheal tube. Dixon's up-and-down method was used to obtain ED₅₀data for women and men separately. The initial dose of oxycodone was 0.2 mg/kg for women and 0.3 mg/kg for men (step size was 0.01 mg/kg). Next, a dose-response curve from the probit analysis was generated to determine the ED₅₀and ED₉₅to blunt the intubation reaction in female and male patients. Adverse events following oxycodone injection were observed for 5 min before propofol injection.

Results

Sixty-three patients were analyzed, including 29 females and 34 males. According to the probit analysis, the ED₅₀ and ED₉₅of oxycodone required to blunt the intubation reaction in women were 0.254 mg/kg (95% confidence interval [CI], 0.220-0.328 mg/kg) and 0.357 mg/kg (95% CI, 0.297-2.563 mg/kg), respectively. In men, the ED₅₀ and ED₉₅were 0.324 mg/kg (95% CI, 0.274-0.381 mg/kg) and 0.454 mg/kg (95% CI, 0.384-2.862 mg/kg), respectively. Men required 28% more oxycodone than women for induction (P < 0.01). The most common adverse events were dizziness (87.3%), vertigo (66.7%), sedation (74.6%), and respiratory depression (66.7%).

Conclusions

Oxycodone can be used for induction to prevent intubation reactions. Gender affected the ED₅₀and ED₉₅of oxycodone for blunting the tracheal intubation reaction.

Efficacy and Safety of Oxycodone Injection for Relieving Cancer Pain: A Study in Japan Consisting of Two Open Trials for Intravenous and Subcutaneous Administration

Pure oxycodone injection became increasingly necessary after oral oxycodone was launched in Japan in 2003. However, trials clarifying the efficacy and safety of injection are rare. Therefore, a multicenter open study on injection was designed and carried out in 2010, resulting in the launch of injection therapy in 2012. As published domestic case reports on efficacy already show widespread prescription, this study aimed to provide useful information for cancer pain relief in Japan and other countries. Our oxycodone injection study consisted of two trials, one of intravenous (S#9131) and the other of subcutaneous (S#9132) administration. The minimum required number of enrolled patients suffering cancer pain was determined to be 70 in S#9131 and 20 in S#9132. These studies had the same dose-titration protocol as the main endpoint, i.e., pain relief rate (PRR) defined as the rate of achieving adequate pain control (APC), as in prior oral oxycodone trials in Japan. In S#9131, PRR was 81.4% (95% confidence interval: 70.3-89.7%), therefore, the null hypothesis of PRR<70% was rejected using the binominal one-sided test (p=0.0217). In S#9132, PRR was 73.7% also surpassing 70%. Safety was also assessed in the same way as in prior trials. The majority of adverse effects were moderate or mild and recovered with no sequelae. As shown above, the injection was considered to be effective and safe in cancer pain treatment. The details of these trials, particularly the dose-titration protocol for achieving APC and route switching information, are expected to enhance injection convenience for prescribers.

Simultaneous determination of acetaminophen and oxycodone in human plasma by LC-MS/MS and its application to a pharmacokinetic study

A simple and rapid liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed and validated for simultaneous determination of acetaminophen and oxycodone in human plasma. Acetaminophen-d4 and oxycodone-d3 were used as internal standards. The challenge encountered in the method development that the high plasma concentration level of acetaminophen made the MS response saturated while the desired lower limit of quantification (LLOQ) for oxycodone was hard to reach was well solved. The analytes were extracted by protein precipitation using acetonitrile. The matrix effect of the analytes was avoided by chromatographic separation using a hydrophilic C₁₈ column coupled with gradient elution. Multiple reaction monitoring in positive ion mode was performed on tandem mass spectrometer employing electrospray ion source. The calibration curves were linear over the concentration ranges of 40.0–8000 ng/mL and 0.200–40.0 ng/mL for acetaminophen and oxycodone, respectively. This method, which could contribute to high throughput analysis and better clinical drug monitoring, was successfully applied to a pharmacokinetic study in healthy Chinese volunteers.

The analgesic efficacy of oxycodone hydrochloride versus fentanyl during outpatient artificial abortion operation: A randomized trial

BACKGROUND

Problems like body movement, respiratory depression, and complained of pain are still common phenomenon in outpatient artificial abortion general anesthesia. Oxycodone hydrochloride is a semisynthetic opioid and has a good therapeutic effect on visceral pain. We hypothesize that oxycodone hydrochloride would be superior to fentanyl in outpatient artificial abortion surgery.

METHODS

In this clinical trial 149 American Society of Anesthesiologists (ASA) I or II female outpatients scheduled for elective artificial abortion surgeries under general anesthesia were randomly divided into 3 groups: oxycodone hydrochloride 0.06 mg/kg group (group A), oxycodone hydrochloride 0.08 mg/kg group (group B), and control group fentanyl 2 ug/kg (group C). The primary outcome was level body movement and respiratory depression during the surgery, the second outcome included the visual analogue scale (VAS) score 30 minutes after waking.

RESULTS

A total of 120 participants completed the study, n = 40 in each group. There was no significant difference in patients' age, body mass index (BMI), preoperative heart rate, mean arterial blood pressure, consumption dose of propofol, intraoperative body movement type and times, and duration of surgery among the 3 groups (P > .05). Comparing the incidence of intraoperative respiratory depression and SPO2 < 90% among the 3 groups, group C's was significantly higher than those of groups A and B, and the difference was statistically significant (P < .05). Group A had no difference compared with group B. In VAS score 30minutes after waking, group C was the highest, followed by group A, with group B as the lowest. The difference among the 3 groups was statistically significant (P < .05), but a difference delta less than 1 on the VAS scale is not clinically significant.

CONCLUSION

The analgesic effect of oxycodone hydrochloride at 0.06 mg/kg applied to painless artificial abortion surgery is not superior than that of fentanyl, but the incidence of intraoperative respiratory depression and hypoxemia is significantly lower than fentanyl.

Perspectives on Intravenous Oxycodone for Control of Postoperative Pain

Intravenous (IV) analgesia has particular advantages in the immediate postoperative period. For example, IV administration results in a faster onset of pain relief and results in more predictable pharmacokinetics than does administration by other routes. It also allows for convenient dosing before or during surgery, permitting the initiation of effective analgesia in the early phase of the postoperative period. In addition, when patients are able to tolerate oral intake, they can be switched from IV to oral dosing based on maintaining the predictable analgesia established by the IV route. IV morphine is widely used for the control of postoperative pain, but there is a trend toward the use of oxycodone. Oxycodone (which may be mediated partly through kappa- as well as mu-opioid receptors) offers several potential advantages. Published studies comparing IV oxycodone to other IV opioids for postsurgical pain report that oxycodone is a safe and effective analgesic. Some studies show that IV oxycodone may be associated with greater pain control, fewer or less severe adverse events, and faster onset of action, although the results are not consistent across all studies. Oxycodone has been reported to be safe in the geriatric and other special populations when adequate clinical adjustments are made. Thus, the clinical reports and oxycodone's pharmacologic profile make intravenous oxycodone a potentially important "new" old drug for postoperative pain control.

Slow drug delivery decreased total body clearance and altered bioavailability of immediate- and controlled-release oxycodone formulations

Oxycodone is a commonly used analgesic with a large body of pharmacokinetic data from various immediate-release or controlled-release formulations, under different administration routes, and in diverse populations. Longer terminal half-lives from extravascular administration as compared to IV administration have been attributed to flip-flop pharmacokinetics with the rate constant of absorption slower than elimination. However, PK parameters from the extravascular studies showed faster absorption than elimination. Sustained release formulations guided by the flip-flop concept produced mixed outcomes in formulation development and clinical studies. This research aims to develop a mechanistic knowledge of oxycodone ADME, and provide a consistent interpretation of diverging results and insight to guide further extended release development and optimize the clinical use of oxycodone. PK data of oxycodone in human studies were collected from literature and digitized. The PK data were analyzed using a new PK model with Weibull function to describe time-varying drug releases/ oral absorption, and elimination dependent upon drug input to the portal vein. The new and traditional PK models were coded in NONMEM. Sensitivity analyses were conducted to address the relationship between rates of drug release/absorption and PK profiles plus terminal half-lives. Traditional PK model could not be applied consistently to describe drug absorption and elimination of oxycodone. Errors were forced on absorption, elimination, or both parameters when IV and PO profiles were fitted separately. The new mechanistic PK model with Weibull function on absorption and slower total body clearance caused by slower absorption adequately describes the complex interplay between oxycodone absorption and elimination in vivo. Terminal phase of oxycodone PK profile was shown to reflect slower total body drug clearance due to slower drug release/absorption from oral formulations. Mechanistic PK models with Weibull absorption functions, and release rate-dependent saturable total body clearance well described the diverging oxycodone absorption and elimination kinetics in the literature. It showed no actual drug absorption during the terminal phase, but slower drug clearance caused by slower release/absorption producing the appearance of flip-flop and offered new insight for the development of modified release formulations and clinical use of oxycodone.