A rapid and sensitive LC-MS/MS method for quantifying oxycodone, noroxycodone, oxymorphone and noroxymorphone in human plasma to support pharmacokinetic drug interaction studies of oxycodone.

A sensitive and reliable LC-MS/MS method was developed and validated for the quantification of oxycodone and metabolites in human plasma. The method has a runtime of 6 min and a sensitivity of 0.1 µg/L for all analytes. Sample preparation consisted of protein precipitation. Separation was performed on a Kinetix biphenyl column (2.1 × 100 mm, 1.7 µm), using ammonium formate 5 mm in 0.1% aqueous formic acid and methanol LC-MS grade 100% in gradient elution at a flow rate of 0.4 ml/min. Detection was performed in multiple reaction monitoring mode using positive electrospray ionization. The method was linear over the calibration range of 0.1-25.0 µg/L for oxycodone, noroxycodone and noroxymorphone and 0.1-5.0 µg/L for oxymorphone. The method demonstrated good performance in terms of intra- and interday accuracy (86.5-110.3%) and precision (CV 1.7-9.3%). The criteria for the matrix effect were met (CV < 15%) except for noroxymorphone, for which an additional method was applied to compensate for the matrix effect. Whole blood samples were stable for 4 h at room temperature. Plasma samples were stable for 24 h at room temperature and 3 months at -20°C. Furthermore, the method was successfully applied in a pharmacokinetic drug interaction study of oxycodone and enzalutamide in patients with prostate cancer.

Oxycodone findings and CYP2D6 function in postmortem cases.

Genetic disposition can cause variation in oxycodone pharmacokinetic characteristics and decrease or increase the expected clinical response. In forensic medicine, determination of cause of death or assessing time between drug intake and death can be facilitated by knowledge of parent and metabolite concentrations. In this study, the aim was to investigate if CYP2D6 genotyping can facilitate interpretation by investigating the frequency of the four CYP2D6 phenotypes, poor metabolizer, intermediate metabolizer, extensive metabolizer, and ultra-rapid metabolizer in postmortem cases, and to study if the CYP2D6 activity was associated with a certain cause of death, concentration, or metabolic ratio. Cases positive for oxycodone in femoral blood (n = 174) were genotyped by pyrosequencing for CYP2D6*3, *4, and *6 and concentrations of oxycodone, noroxycodone, oxymorphone, and noroxymorphone were determined by LC-MS/MS (LLOQ 0.005 µg/g). Digital droplet PCR was used to determine the copy number variation for CYP2D6*5. Cases were categorized by cause of death. It was found that poor and intermediate CYP2D6 metabolizers had significantly higher oxycodone and noroxycodone concentrations compared to extensive and ultra-rapid metabolizers. CYP2D6 phenotype were equally distributed between cause of death groups, showing that no phenotype was overrepresented in any of the cause of death groups. We also found that the concentration ratio between oxymorphone and oxycodone depended on the CYP2D6 activity when death was unrelated to intoxication. In general, a low metabolite to parent ratio indicate an acute intake. By using receiver operating characteristic (ROC) analysis, we conclude that an oxymorphone/oxycodone ratio lower than 0.075 has a high sensitivity for separating intoxications with oxycodone from other intoxications and non-intoxications. However, the phenotype needs to be known to reach a high specificity. Therefore, the ratio should not be used as a biomarker on its own to distinguish between different causes of death but needs to be complemented by genotyping.

Maternal continuous oral oxycodone self-administration alters pup affective/social communication but not spatial learning or sensory-motor function.

BACKGROUND: The broad use/misuse of prescription opioids during pregnancy has resulted in a surge of infants with Neonatal Opioid Withdrawal Syndrome (NOWS). Short-term irritability and neurological complications are its hallmarks, but the long-term consequences are unknown. METHODS: A newly-developed preclinical model of oxycodone self-administration enables adult female rats to drink oxycodone (∼10/mg/kg/day) before and during pregnancy, and after delivery, and to maintain normal liquid intake, titrate dosing, and avoid withdrawal. RESULTS: Oxycodone was detected in the serum of mothers and pups. Growth parameters in dams and pups and litter mass and size were similar to controls. There were no differences in paw retraction latency to a thermal stimulus between Oxycodone and Control pups at postnatal (PN) 2 or PN14. Oxycodone and Control pups had similar motor coordination, cliff avoidance, righting time, pivoting, and olfactory spatial learning from PN3 through PN13. Separation-induced ultrasonic vocalizations at PN8 revealed higher call frequency in Oxycodone pups relative to Control pups (p<0.031; Cohen's d=1.026). Finally, Oxycodone pups displayed withdrawal behaviors (p's<0.029; Cohen's d's>0.806), and Oxycodone males only vocalized more than Control pups in the first minute of testing (p's<0.050; Cohen's d's>.866). Significant effects were corroborated by estimation plots. CONCLUSIONS: Our rat model of oral oxycodone self-administration in pregnancy shows exacerbated affect/social communication in pups in a sex-dependent manner but spared cognition and sensory-motor behaviors. This preclinical model reproduces selective aspects of human opioid use during pregnancy, enabling longitudinal analysis of how maternal oxycodone changes emotional behavior in the offspring.

Electrochemical sensor based on glassy carbon electrode modified by polymelamine formaldehyde/graphene oxide nanocomposite for ultrasensitive detection of oxycodone.

Polymelamine formaldehyde/graphene oxide (PMF/GO) nanocomposite was used, for the first time, to study the ultrasensitive and selective electrochemical detection of oxycodone (OXC). The successful characterization of PMF/GO was verified based on scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and Raman spectroscopy. The modified GCE (PMF/GO-GCE) proved its electrocatalytic effect on OXC determination according to cyclic, linear sweep, and differential pulse voltammetry (CV, LSV, and DPV) and electrochemical impedance spectroscopy (EIS) studies. The developed sensor under optimal conditions offered a linear relationship in a limited range of  0.01 to 45 µmol L-1 with the limit of detection (LOD) of 2.0 nmol L-1. The proposed PMF/GO-GCE sensor was effectively employed for the OXC detection in human urine and serum samples. Graphical abstract.

Oxycodone Concentrations and Metabolic Ratios in Femoral Blood from Fatal Intoxications and Other Causes of Death using LC-MS-MS.

Oxycodone (OC) is an opioid with strong analgesic effects widely used to treat acute and chronic pain. Interpretation of OC concentrations in postmortem cases is complicated due to tolerance and overlapping concentrations for fatal and non-fatal levels. In this study, our aim was to develop and validate a method for OC and its three metabolites: noroxycodone (NOC), oxymorphone (OM) and noroxymorphone (NOM) in postmortem femoral blood. Our goal was to define reference concentrations for intoxications and non-intoxications and investigate metabolic ratios in different causes of death. A rapid LC-MS-MS method using protein-precipitated postmortem blood was developed. Lower limit of quantitation was 0.005 µg/g blood for all analytes; upper limit of quantitation was 1.0 µg/g for OC and NOC and 0.25 µg/g for OM and NOM. The method displayed high precision (3.3-7.7%) and low bias (-0.3 to 12%). In total, 192 cases were analyzed and concentrations ranged from 0.005 to 13 µg/g for OC, 0.005 to 2.0 µg/g for NOC, 0.005 to 0.24 µg/g for OM, and 0.005 to 0.075 µg/g for NOM. We found a significant difference in OC concentration between the cases where OC contributed and those where it did not. In spite of that, we do not recommend the use of a specific blood concentration to distinguish fatal intoxications. Instead, the percentiles from our data set suggest that concentrations >0.2 µg/g are likely to have contributed to toxicity, but that concentrations as high as 0.3 might be tolerated without toxic effects. In addition, we also found that a low NOC/OC ratio could point toward an acute fatal intoxication. In conclusion, the OC concentration alone may not be sufficient to diagnose a fatal intoxication.

Postmortem Brain-Blood Ratios of Codeine, Fentanyl, Oxycodone and Tramadol.

The analgesics, codeine, fentanyl, oxycodone and tramadol, frequently occur in postmortem cases and determining their role in the cause of death can be challenging. However, postmortem blood is susceptible to redistribution and may not be available in cases of severe blood loss, putrefaction or burns. Brain tissue may serve as a viable supplement to blood or on its own, as it is resistant to postmortem redistribution and often available as a sample matrix when blood is not available. We present brain and blood concentrations and brain-blood ratios of the four analgesics from 210 autopsy cases. The cases were classified according to the presumed cause of death: A: The compound was believed to have solely caused a fatal intoxication. B: The compound was assumed to have contributed to a fatal outcome in combination with other drugs, alcohol or disease. C: The compound was not regarded as being related to the cause of death. Blood and brain samples were prepared by automatic solid phase extraction and quantified by liquid chromatography-mass spectrometry. The squared correlation coefficients between concentrations in brain tissue and blood ranged 0.45-0.91. The median brain-blood ratios were codeine 1.8 (range 0.47-4.6), fentanyl 2.1 (range 0.29-16), oxycodone 1.8 (range 0.11-6.0) and tramadol 1.8 (range 0.047-6.8). A significantly higher brain-blood ratio of codeine was observed in cases where heroin had been administered, although there was a wide overlap. Intravenous and transdermal fentanyl administration could not be distinguished based on the blood or brain concentration or the brain-blood ratio. The results of this study may benefit the toxicological investigation in postmortem cases where one of the four analgesics are suspected of having contributed to or caused a fatal intoxication.

Quantification of serum levels in mice of seven drugs (and six metabolites) commonly taken by older people with polypharmacy.

Polypharmacy (use of ≥ 5 drugs) is common in older people but has minimal preclinical or clinical evidence of safety or efficacy and is associated with adverse outcomes in older people. Drug-drug interactions are poorly understood beyond drug pairs. An efficient and sensitive method to measure multiple serum drugs and metabolites could inform drug dosing in polypharmacy. Development of a sensitive liquid chromatography - tandem mass spectrometry method to simultaneously measure seven drugs and their respective metabolites in serum in a preclinical model of polypharmacy. This method was validated for optimal recovery, matrix effect, limit of quantification (LOQ), inter- and intra-day variability, and carry over. Serum samples from mice (n = 5-6/group) treated with chronic oral doses of three polypharmacy regimens and five monotherapies were screened for drug and metabolite levels (metoprolol, α-hydroxymetoprolol, O-desmethylmetoprolol, omeprazole, 5-hydroxyomeprazole, omeprazole sulphone, acetaminophen, irbesartan, citalopram, oxybutynin, oxycodone, noroxycodone, oxymorphone and tenivastatin). The LOQ for the compounds ranged from 0.05 to 0.1 ng/mL in serum. Recovery, matrix effect, and inter- and intra-day variability peak response were acceptable. No carry over was observed at the concentrations tested. Analytes were detectable in mice treated with these drugs, and differences in drug levels were observed with different polypharmacy and monotherapy regimens. The method is sensitive and robust to measure parent drugs and metabolites simultaneously in the context of polypharmacy. Polypharmacy appeared to affect drug levels in a preclinical model. This model can be used to understand pharmacokinetics of chronic polypharmacy, which could inform prescribing and improve outcomes for older people.

Female and male rats readily consume and prefer oxycodone to water in a chronic, continuous access, two-bottle oral voluntary paradigm.

The increasing abuse of opioids - such as oxycodone - poses major challenges for health and socioeconomic systems. Human prescription opioid abuse is marked by chronic, voluntary, oral intake and sex differences. To develop interventions, the field would benefit from a preclinical paradigm that similarly provides rodents with chronic, continuous, oral, voluntary and free-choice access to oxycodone. Here we show female and male rats voluntarily ingest and choose oxycodone over water and show both dependence and motivation to take oxycodone during a chronic oral voluntary, two-bottle choice, continuous access paradigm. Adult female and male Long-Evans rats were given unlimited, continuous homecage access to two bottles containing water (Control) or one bottle of water and one bottle of oxycodone dissolved in water (Experimental). Virtually all experimental rats voluntarily drank oxycodone (~10 mg/kg/day) and escalated their intake over 22 weeks. Females self-administered twice as much oxycodone by body weight (leading to higher blood levels of oxycodone) and engaged in more gnawing behavior of wooden blocks relative to males. Precipitated withdrawal revealed high levels of dependence in both sexes. Reflecting motivation to drink oxycodone, ascending concentrations of citric acid suppressed the intake of oxycodone (Experimental) and the intake of water (Control); however, Experimental rats returned to pre-citric acid preference levels whereas Controls rats did not. Pre-screening behaviors of rats on open field exploration predicted oxycodone intake. Thus, rats consumed and preferred oxycodone over time in this chronic two-bottle oral choice paradigm and both sexes displayed many features of human oxycodone abuse.

Oxycodone for pain management in the latent phase of labour - A pragmatic trial.

BACKGROUND: Parenteral opioids are used for pain relief in labour but there are little data for oxycodone in this context. The aim of this study was to evaluate the efficacy, foetal exposure and safety of subcutaneous oxycodone in the latent phase of labour. METHODS: This pragmatic trial included 76 parturients, who received subcutaneous oxycodone for pain relief in the latent phase of labour according to the hospital protocol: an initial dose 0.1 mg/kg, and a second dose, 0.05 mg/kg, could be administered four hours later. Pain intensity and pain relief were assessed using a numerical rating scale of 0-10. After delivery, blood samples from the maternal and umbilical veins were collected, and plasma concentrations of oxycodone and its main metabolites were quantified using UPLC-MS/MS. The Apgar scores and maternal and neonatal adverse effects were recorded. RESULTS: The foetal exposure at birth was low, the median oxycodone and oxymorphone umbilical vein plasma concentrations were 1.2 ng/mL (range 0.21-7.8) and 0.14 ng/mL (0-0.26), respectively. Pain scores decreased substantially, from a median pain score of 7/10 before oxycodone to median scores of 5/10 at 30 minutes after administration, 5/10 at 60 minutes and 6/10 at 120 minutes. The median Apgar score was 9 (range 2-10) at 1 minute and 9 (6-10) at 5 minutes. Maternal adverse effects were mild, and there were no oxycodone-related neonatal adverse effects. CONCLUSION: Subcutaneous oxycodone provided effective analgesia during the latent phase of labour. Newborn exposure at birth was low, and oxycodone was well-tolerated.

Sex differences in oral oxycodone self-administration and stress-primed reinstatement in rats.

The opioid epidemic has become a severe public health problem, with approximately 130 opioid-induced deaths occurring each day in the United States. Prescription opioids are responsible for approximately 40% of these deaths. Oxycodone is one of the most commonly abused prescription opioids, but despite its prevalent misuse, the number of preclinical studies investigating oxycodone-seeking behaviors is relatively limited. Furthermore, preclinical oxycodone studies that include female subjects are even more scarce, and it is critical that future work includes both sexes. Additionally, the oral route of administration is one of the most common routes for recreational users, especially in the early stages of drug experimentation. However, currently, only two studies have been published investigating operant oral oxycodone self-administration in rodents. Therefore, the primary goal of the present study was to establish an oral oxycodone operant self-administration model in adult male and female rats, as well as to examine a potential mechanism of stress-primed reinstatement. We found that females consumed significantly more oral oxycodone than males in operant self-administration sessions. We also found that active oxycodone self-administration was reduced by mu opioid receptor antagonism and by substitution of water for oxycodone solution. Lastly, we induced stress-primed reinstatement and found that this behavior was significantly attenuated by antagonism of the neurokinin-1 receptor, consistent with our prior work examining stress-induced reinstatement of alcohol- and cocaine-seeking.

Oral prescription opioid-seeking behavior in male and female mice.

A significant portion of prescription opioid users self-administer orally rather than intravenously. Animal models of opioid addiction have demonstrated that intravenous cues are sufficient to cause drug seeking. However, intravenous models may not characterize oral users, and the preference to self-administer orally appears to be partially influenced by the user's sex. Our objectives were to determine whether oral opioid-associated cues are sufficient for relapse and whether sex differences exist in relapse susceptibility. Mice orally self-administered escalating doses of oxycodone under postprandial (prefed) or non-postprandial (no prefeeding) conditions. Both sexes demonstrated cue-induced reinstatement following abstinence. In separate mice, we found that oral oxycodone cues were sufficient to reinstate extinguished oral oxycodone-seeking behavior following abstinence without prior postprandial or water self-administration training. During self-administration, we incidentally found that female mice earned significantly more mg/kg oxycodone than male mice. Follow-up studies indicated sex differences in psychomotor stimulation and plasma oxycodone/oxymorphone following oral oxycodone administration. In addition, gonadal studies were performed in which we found divergent responses where ovariectomy-enhanced and orchiectomy-suppressed oral self-administration. While the suppressive effects of orchiectomy were identified across doses and postprandial conditions, the enhancing effects of ovariectomy were selective to non-postprandial conditions. These studies establish that (a) oral drug cues are sufficient to cause reinstatement that is independent of prandial conditions and water-seeking behavior, (b) earned oral oxycodone is larger in female mice compared with male mice potentially through differences in psychomotor stimulation and drug metabolism, and (c) gonadectomy produces divergent effects on oral oxycodone self-administration between sexes.

Oxycodone concentrations in the central nervous system and cerebrospinal fluid after epidural administration to the pregnant ewe.

The main sites of the analgesic action of oxycodone are the brain and spinal cord. The present study describes the concentrations of oxycodone and its metabolites in the brain and spinal cord after epidural administration to the ewe. Twenty pregnant ewes undergoing laparotomy were randomized into two groups to receive epidural oxycodone: infusion group (n = 10, 0.1 mg·kg-1 bolus followed by continuous infusion of 0.05 mg·kg-1 ·h-1 for five days) or repeated boluses group (n = 10, 0.2 + 2x0.1 mg·kg-1 bolus followed by a 0.2 mg·kg-1 bolus every 12 hours for five days). After five days of oxycodone administration, arterial blood samples were collected, the sheep were killed, and a CSF sample and tissue samples from the cortex, thalamus, cerebellum and spinal cord were obtained for the quantification of oxycodone and its main metabolites. The median plasma and CSF concentrations of oxycodone were 9.0 and 14.2 ng·mL-1 after infusion and 0.4 and 1.1 ng·mL-1 after repeated boluses. In the infusion group, the cortex, thalamus and cerebellum oxycodone concentrations were 4-8 times higher and in the spinal cord 1310 times higher than in plasma. In the repeated boluses group, brain tissue concentrations were similar in the three areas, and in the spinal cord were 720 times higher than in plasma. Oxymorphone was the main metabolite detected, which accumulated in the brain and spinal cord tissue. In conclusion, first, accumulation of oxycodone and oxymorphone in the CNS was observed, and second, high spinal cord concentrations suggest that epidural oxycodone may provide segmental analgesia.

Testing for midazolam and oxycodone in blood after formalin-embalmment: About a complex medico-legal case.

The stability of compounds in formalin solution is an important factor for drug analysis in a toxicological investigation. In this article, the authors report a complex medico-legal case involving midazolam and oxycodone. The complexity of this case comes from the fact that the body was embalmed with formalin solution before the autopsy. This technique, called thanatopraxy, allows the preservation of corpses from decomposition, the destruction of a maximal number of micro-organisms, and the presentation of the body with a natural appearance to the family. Unfortunately, when thanatopraxy is performed before the collection of biological specimens, the toxicological results are not representative of the time of the death. In addition, the interpretation of the results is difficult, because formalin can cause oxidation of xenobiotics present in the body at the time of the death, alter the pH of the tissues and dilute the compounds. To document the chemical stability of midazolam and oxycodone in formalin solution and interpret the results, a stability study was conducted for 21 days. Blood containing midazolam and oxycodone was spiked with formalin, kept at 4°C and regularly tested for both drugs. This study showed a rapid degradation of midazolam and oxycodone (85% during the first 24 hours for oxycodone). In the peripheral blood of the victim, methanol (1.31 g/L), midazolam (74ng/mL) and oxycodone (152 ng/mL) were identified. According to the stability study, the measured concentrations in formalin fixed-tissues are to be interpreted very carefully, knowing that significant degradation has occurred.

An alternating polarity switching assay for quantification of oxycodone and topiramate: An application of LC-MS/MS method in support to PK/PD study in rodents.

In mass spectrometry, compounds that have different ionization properties experience challenges in simultaneous analysis. In the present paper, the authors proposed a polarity switching (+ve and -ve) LC-MS/MS method to analyze oxycodone and topiramate in a single run. The developed method was validated in the range of 5-1000 ng/mL for oxycodone and 20-5000 ng/mL for topiramate as per the US FDA guidelines. The mass spectrometer was operated in multiple reaction monitoring (MRM) mode to analyze oxycodone and topiramate simultaneously using oxycodone-d6 and topiramate-d12 as internal standards, respectively. Sample preparation was performed in 96-well protein precipitation plates using acetonitrile. Processed samples were analyzed using a C18 column with a gradient mobile phase composed of 10 mm ammonium formate with 0.1% formic acid and acetonitrile. The method was validated for selectivity, specificity, linearity, precision and accuracy, dilution integrity and stability. After validation, this method was successfully applied to quantify oxycodone and topiramate in plasma of concomitantly treated Sprague Dawley (SD) rats.

A prospective, randomized, open label, controlled study investigating the efficiency and safety of 3 different methods of rectus sheath block analgesia following midline laparotomy.

BACKGROUND: There is a controversy regarding the efficacy of rectus sheath block (RSB). The aim of the present study was to evaluate analgesic efficacy and safety of three different methods of RSB in postoperative pain management after midline laparotomy. METHODS: A prospective, randomized, controlled, open-label clinical trial with 4 parallel groups was conducted in a tertiary care hospital in Finland. A total of 57 patients undergoing midline laparotomy were randomized to the control group (n = 12) or to 1 of the 3 active RSB analgesia groups: single-dose (n = 16), repeated-doses (n = 12), or continuous infusion (n = 17). Opioid consumption with iv-patient-controlled analgesia pump was recorded, and pain scores and patients' satisfaction were surveyed on an 11-point numeric rating scale for the first 48 postoperative h. Plasma concentrations of oxycodone and levobupivacaine were analyzed. All adverse events during the hospital stay were recorded. RESULTS: Oxycodone consumption was less during the first 12 h in the repeated-doses and in the continuous infusion groups (P = .07) and in numerical values up to 48 h in the repeated-doses group. Plasma oxycodone concentrations were similar in all 4 groups. Pain scores were lower in the repeated-doses group when coughing during the first 4 h (P = .048 vs. control group), and at rest on the first postoperative morning (P = .034 vs. the other 3 groups) and at 24 h (P = .006 vs. the single-dose group). All plasma concentrations of levobupivacaine were safe. The patients' satisfaction was better in the repeated-doses group compared with the control group (P = .025). No serious or unexpected adverse events were reported. CONCLUSIONS: RSB analgesia with repeated-doses seems to have opioid sparing efficacy, and it may enhance pain relief and patients' satisfaction after midline laparotomy.

Determination of oxycodone and its major metabolites in haematic and urinary matrices: Comparison of traditional and miniaturised sampling approaches.

Oxycodone is a widely prescribed, full agonist opioid analgesic. As such, it is used clinically to treat different kinds of painful conditions, with a relatively high potential for doping practices in athletes. In this paper, different classic and innovative miniaturised matrices from blood and urine have been studied and compared, to evaluate their relative merits and drawbacks within therapeutic drug monitoring (TDM) and to implement new protocols for anti-doping analysis. Plasma, dried blood spots (DBS) and dried plasma spots (DPS) have been studied for TDM purposes, while urine, dried urine spots (DUS) and volumetric absorptive microsamples (VAMS) from urine for anti-doping. These sampling techniques were coupled to an original bioanalytical method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the evaluation and monitoring of the levels of oxycodone and its major metabolites (noroxycodone and oxymorphone) in patients under pain management and in athletes. The method was validated according to international guidelines, with good results in terms of precision, extraction yield and accuracy for all considered micromatrices. Thus, the proposed sampling, pre-treatment and analysis are attractive strategies for oxycodone determination in human blood and urine, with advanced options for application to derived micromatrices. Microsampling procedures have significant advantages over classic biological matrices like simplified sampling, storage and processing, but also in terms of precision (<9.0% for DBS, <7.7% for DPS, <7.1% for DUS, <5.3% for VAMS) and accuracy (>73% for DBS, >78% for DPS, >74% for DUS, >78% for VAMS). As regards extraction yield, traditional and miniaturised sampling approaches are comparable (>67% for DBS, >74% for DPS, >75% for DUS, >75% for VAMS). All dried matrices have very low volumes, leading to a significant advantage in terms of analysis feasibility. On the other hand, this also leads to a corresponding decrease in the overall sensitivity.

Effectiveness and Safety of Once-Daily Extended-Release Hydrocodone in Individuals Previously Receiving Immediate-Release Oxycodone for Chronic Pain.

Objectives: This study evaluated the safety and effectiveness of a once-daily, single-entity, extended-release hydrocodone bitartrate (HYD) among patients with chronic noncancer and non-neuropathic pain who required opioid rotation from a previous analgesic regimen that primarily consisted of immediate-release (IR) oxycodone. Methods: Post hoc analyses of a primary study that assessed HYD 20 to 120 mg over a 52-week period are presented. The primary study included a dose titration period (up to 45 days), a 52-week maintenance period, and an optional taper period (up to 14 days). Results: Relative to baseline, mean "average pain over the last 24 hours" declined by 1.9 points at the end of the titration period and by 2.6 points at the end of the maintenance period. Additionally, interference and severity of pain as measured by the Brief Pain Inventory-Short Form decreased by 2.3 and 1.9 points, respectively, during the maintenance period. The use of supplemental opioid analgesics decreased. Most patients remained on a stable HYD dose throughout the maintenance period. Most patients indicated satisfaction with HYD and considered it convenient and easy to use. HYD demonstrated a safety profile typical of µ opioids; nausea, constipation, vomiting, and dizziness were the most frequently reported opioid-related adverse events during the study. Conclusions: In patients with chronic pain who received HYD over a 52-week period, treatment was generally well tolerated and provided effective analgesia among those who rotated from a pain regimen primarily consisting of IR oxycodone.

Analgesic Plasma Concentrations of Oxycodone After Surgery for Breast Cancer-Which Factors Matter?

We investigated factors affecting analgesic oxycodone concentrations after breast cancer surgery in 1,000 women. Preoperatively, we studied heat and cold pain sensitivities and anxiety scores. Postoperatively, rest and motion pain intensities were measured and intravenous oxycodone was administered until satisfactory analgesia. At this point, the mean oxycodone concentration (variation coefficient) was 33.3 ng/mL (66%) and it was 21.7 ng/mL (69%) when the patient requested oxycodone again. At both time points, the concentrations varied >100-fold between individuals. The analgesic oxycodone concentration was increased by 21.3% per motion pain intensity score on a 0-10 scale and by 22.3% if axillary clearance was performed instead of sentinel node biopsy (P < 0.001). Forty-seven women who were older and less anxious than others (P < 0.01) required no oxycodone. Anxiety, age, chronic pain, or preoperative pain sensitivity were not independently associated with the analgesic oxycodone concentration. CYP2D6 and CYP3A genotypes did not affect analgesic concentration or duration of analgesia.

Prediction of human CNS pharmacokinetics using a physiologically-based pharmacokinetic modeling approach.

Knowledge of drug concentration-time profiles at the central nervous system (CNS) target-site is critically important for rational development of CNS targeted drugs. Our aim was to translate a recently published comprehensive CNS physiologically-based pharmacokinetic (PBPK) model from rat to human, and to predict drug concentration-time profiles in multiple CNS compartments on available human data of four drugs (acetaminophen, oxycodone, morphine and phenytoin). Values of the system-specific parameters in the rat CNS PBPK model were replaced by corresponding human values. The contribution of active transporters for the four selected drugs was scaled based on differences in expression of the pertinent transporters in both species. Model predictions were evaluated with available pharmacokinetic (PK) data in human brain extracellular fluid and/or cerebrospinal fluid, obtained under physiologically healthy CNS conditions (acetaminophen, oxycodone, and morphine) and under pathophysiological CNS conditions where CNS physiology could be affected (acetaminophen, morphine and phenytoin). The human CNS PBPK model could successfully predict their concentration-time profiles in multiple human CNS compartments in physiological CNS conditions within a 1.6-fold error. Furthermore, the model allowed investigation of the potential underlying mechanisms that can explain differences in CNS PK associated with pathophysiological changes. This analysis supports the relevance of the developed model to allow more effective selection of CNS drug candidates since it enables the prediction of CNS target-site concentrations in humans, which are essential for drug development and patient treatment.