Oxycodone: a review of its use in the management of pain

Genetic background and sex influence somatosensory sensitivity and oxycodone analgesia in the Hybrid Rat Diversity Panel

Opioid use disorder (OUD) is an ongoing public health concern in the United States, and relatively little work has addressed how genetic background contributes to OUD. Understanding the genetic contributions to oxycodone-induced analgesia could provide insight into the early stages of OUD development. Here, we present findings from a behavioral phenotyping protocol using several inbred strains from the Hybrid Rat Diversity Panel. Our behavioral protocol included a modified "up-down" von Frey procedure to measure inherent strain differences in the sensitivity to a mechanical stimulus on the hindpaw. We also performed the tail immersion assay, which measures the latency to display tail withdrawal in response to a hot water bath. Initial withdrawal thresholds were taken in drug-naïve animals to record baseline thermal sensitivity across the strains. Oxycodone-induced analgesia was measured after administration of oxycodone over the course of 2 h. Both mechanical and thermal sensitivity are shaped by genetic factors and display moderate heritability (h2 = 0.23-0.40). All strains displayed oxycodone-induced analgesia that peaked at 15-30 min and returned to baseline by 2 h. There were significant differences between the strains in the magnitude and duration of their analgesic response to oxycodone, although the heritability estimates were quite modest (h2 = 0.10-0.15). These data demonstrate that genetic background confers differences in mechanical sensitivity, thermal sensitivity, and oxycodone-induced analgesia.

A Multicenter Retrospective Observational Study Analyzing the Effect of Polypharmacy on Oxycodone Tolerability

Polypharmacy is becoming increasingly troublesome in the treatment of cancer. The aim of this study was to explore the effects of concomitant polypharmacy comprising drugs that inhibit CYP3A4 and/or CYP2D6 on the oxycodone tolerability in patients with cancer. We conducted a multicenter retrospective study encompassing 20 hospitals. The data used for the study were obtained during the first 2 wk of oxycodone administration. The incidence of oxycodone discontinuation or dose reductions due to side effects and oxycodone-induced nausea and vomiting (OINV) were compared between patients not treated with either inhibitor and those treated with concomitant CYP3A4 or CYP2D6 inhibitors. The incidence of oxycodone discontinuation or dose reductions in patients treated with ≥3 concomitant CYP2D6 inhibitors (18.2%) tended to be higher than that in patients without this treatment (8.2%; p = 0.09). Moreover, the incidence of OINV in patients treated with 2 concomitant CYP3A4 inhibitors (29.8%) was significantly higher than that in patients without this treatment (15.5%; p = 0.049). Multivariate analysis showed that more than two concomitant CYP3A4 inhibitors and no concomitant use of naldemedine were independent risk factors for OINV. Concomitant polypharmacy involving CYP3A4 inhibitors increases the risk of OINV. Therefore, medications concomitantly used with oxycodone should be optimized.

Oxycodone: A Current Perspective on Its Pharmacology, Abuse, and Pharmacotherapeutic Developments

Oxycodone, a semisynthetic derivative of naturally occurring thebaine, an opioid alkaloid, has been available for more than 100 years. Although thebaine cannot be used therapeutically due to the occurrence of convulsions at higher doses, it has been converted to a number of other widely used compounds that include naloxone, naltrexone, buprenorphine, and oxycodone. Despite the early identification of oxycodone, it was not until the 1990s that clinical studies began to explore its analgesic efficacy. These studies were followed by the pursuit of several preclinical studies to examine the analgesic effects and abuse liability of oxycodone in laboratory animals and the subjective effects in human volunteers. For a number of years oxycodone was at the forefront of the opioid crisis, playing a significant role in contributing to opioid misuse and abuse, with suggestions that it led to transitioning to other opioids. Several concerns were expressed as early as the 1940s that oxycodone had significant abuse potential similar to heroin and morphine. Both animal and human abuse liability studies have confirmed, and in some cases amplified, these early warnings. Despite sharing a similar structure with morphine and pharmacological actions also mediated by the μ-opioid receptor, there are several differences in the pharmacology and neurobiology of oxycodone. The data that have emerged from the many efforts to analyze the pharmacological and molecular mechanism of oxycodone have generated considerable insight into its many actions, reviewed here, which, in turn, have provided new information on opioid receptor pharmacology. SIGNIFICANCE STATEMENT: Oxycodone, a μ-opioid receptor agonist, was synthesized in 1916 and introduced into clinical use in Germany in 1917. It has been studied extensively as a therapeutic analgesic for acute and chronic neuropathic pain as an alternative to morphine. Oxycodone emerged as a drug with widespread abuse. This article brings together an integrated, detailed review of the pharmacology of oxycodone, preclinical and clinical studies of pain and abuse, and recent advances to identify potential opioid analgesics without abuse liability.

Dexmedetomidine-Oxycodone combination for conscious sedation during colonoscopy in obese patients: A randomized controlled trial

Background

Obesity is a risk factor for sedation-related respiratory depression during colonoscopy. In a colonoscopy, propofol is frequently used because of its strong sedative and hypnotic properties. However, propofol is associated with marked respiratory depression. The objective of this trial was to investigate the effectiveness and safety of dexmedetomidine plus oxycodone for conscious sedation during colonoscopy in obese patients.

Methods

A total of 120 patients had colonoscopies, and they were divided into two groups at random: Dexmedetomidine and oxycodone were used to sedate group Dex + oxy; while group Pro + oxy received anesthesia with propofol plus oxycodone. Parameters including blood pressure, heart rate, respiration, blood oxygen saturation, injection pain, and recovery time were recorded for both groups.

Results

The incidence of hypoxemia was significantly reduced in group Dex + oxy compared with group Pro + oxy (4.9% vs 20.3%, P = 0.011). Blood pressure was lower, and heart rate was higher in group Pro + oxy compared with group Dex + oxy (P < 0.05). In addition, group Dex + oxy showed a significantly shorter caecal insertion time, recovery time to orientation, and recovery time to walking than group Pro + oxy (P < 0.05). Endoscopist satisfaction scores were significantly higher in group Dex + oxy compared with group Pro + oxy (P = 0.042).

Conclusion

For obese patients, dexmedetomidine plus oxycodone effectively sedate them with few adverse effects, while also reducing colonoscopy operation difficulty by allowing obese patients to reposition. Thus, dexmedetomidine plus oxycodone could be used safely as a conscious sedation method for colonoscopy in obese patients.

Trial registration

The protocol was registered at www.chictr.org.cn (ChiCTR1800017283, July 21, 2018).

Oxycodone decreases anxiety-like behavior in the elevated plus-maze test in male and female rats

The prescription opioid oxycodone is widely used for the treatment of pain in humans. Oxycodone misuse is more common among people with an anxiety disorder than those without one. Therefore, oxycodone might be misused for its anxiolytic properties. We investigated if oxycodone affects anxiety-like behavior in adult male and female rats. The rats were treated with oxycodone (0.178, 0.32, 0.56, or 1 mg/kg), and anxiety-like behavior was investigated in the elevated plus-maze test. Immediately after the elevated plus-maze test, a small open field test was conducted to determine the effects of oxycodone on locomotor activity. In the elevated plus-maze test, oxycodone increased the percentage of time spent on the open arms, the percentage of open arm entries, time on the open arms, open arm entries, and the distance traveled. The males treated with vehicle had a lower percentage of open arm entries than the females treated with vehicle, and oxycodone treatment led to a greater increase in the percentage of open arm entries in the males than females. Furthermore, the females spent more time on the open arms, made more open arm entries, spent less time in the closed arms, and traveled a greater distance than the males. In the small open field test, treatment with oxycodone did not affect locomotor activity or rearing. Sex differences were observed; the females traveled a greater distance and displayed more rearing than the males. In conclusion, oxycodone decreases anxiety-like behavior in rats, and oxycodone has a greater anxiolytic-like effect in males than females.

Oxycodone for cancer-related pain

BACKGROUND

Many people with cancer experience moderate to severe pain that requires treatment with strong opioids, such as oxycodone and morphine. Strong opioids are, however, not effective for pain in all people, neither are they well tolerated by all people. The aim of this review was to assess whether oxycodone is associated with better pain relief and tolerability than other analgesic options for adults with cancer pain. This is an updated Cochrane review previously published in 2017.

OBJECTIVES

To assess the effectiveness and tolerability of oxycodone by any route of administration for pain in adults with cancer.

SEARCH METHODS

For this update, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library, MEDLINE and MEDLINE In-Process (Ovid), Embase (Ovid), Science Citation Index, Conference Proceedings Citation Index - Science (ISI Web of Science), BIOSIS (ISI), and PsycINFO (Ovid) to November 2021. We also searched four trial registries, checked the bibliographic references of relevant studies, and contacted the authors of the included studies. We applied no language, date, or publication status restrictions.

SELECTION CRITERIA

We included randomised controlled trials (parallel-group or cross-over) comparing oxycodone (any formulation or route of administration) with placebo or an active drug (including oxycodone) for cancer background pain in adults by examining pain intensity/relief, adverse events, quality of life, and participant preference.

DATA COLLECTION AND ANALYSIS

Two review authors independently sifted the search, extracted data and assessed the included studies using standard Cochrane methodology. We meta-analysed pain intensity data using the generic inverse variance method, and pain relief and adverse events using the Mantel-Haenszel method, or summarised these data narratively along with the quality of life and participant preference data. We assessed the overall certainty of the evidence using GRADE.

MAIN RESULTS

For this update, we identified 19 new studies (1836 participants) for inclusion. In total, we included 42 studies which enrolled/randomised 4485 participants, with 3945 of these analysed for efficacy and 4176 for safety. The studies examined a number of different drug comparisons. Controlled-release (CR; typically taken every 12 hours) oxycodone versus immediate-release (IR; taken every 4-6 hours) oxycodone Pooled analysis of three of the four studies comparing CR oxycodone to IR oxycodone suggest that there is little to no difference between CR and IR oxycodone in pain intensity (standardised mean difference (SMD) 0.12, 95% confidence interval (CI) -0.1 to 0.34; n = 319; very low-certainty evidence). The evidence is very uncertain about the effect on adverse events, including constipation (RR 0.71, 95% CI 0.45 to 1.13), drowsiness/somnolence (RR 1.03, 95% CI 0.69 to 1.54), nausea (RR 0.85, 95% CI 0.56 to 1.28), and vomiting (RR 0.66, 95% CI 0.38 to 1.15) (very low-certainty evidence). There were no data available for quality of life or participant preference, however, three studies suggested that treatment acceptability may be similar between groups (low-certainty evidence). CR oxycodone versus CR morphine The majority of the 24 studies comparing CR oxycodone to CR morphine reported either pain intensity (continuous variable), pain relief (dichotomous variable), or both. Pooled analysis indicated that pain intensity may be lower (better) after treatment with CR morphine than CR oxycodone (SMD 0.14, 95% CI 0.01 to 0.27; n = 882 in 7 studies; low-certainty evidence). This SMD is equivalent to a difference of 0.27 points on the Brief Pain Inventory scale (0-10 numerical rating scale), which is not clinically significant. Pooled analyses also suggested that there may be little to no difference in the proportion of participants achieving complete or significant pain relief (RR 1.02, 95% CI 0.95 to 1.10; n = 1249 in 13 studies; low-certainty evidence). The RR for constipation (RR 0.75, 95% CI 0.66 to 0.86) may be lower after treatment with CR oxycodone than after CR morphine. Pooled analyses showed that, for most of the adverse events, the CIs were wide, including no effect as well as potential benefit and harm: drowsiness/somnolence (RR 0.88, 95% CI 0.74 to 1.05), nausea (RR 0.93, 95% CI 0.77 to 1.12), and vomiting (RR 0.81, 95% CI 0.63 to 1.04) (low or very low-certainty evidence). No data were available for quality of life. The evidence is very uncertain about the treatment effects on treatment acceptability and participant preference. Other comparisons The remaining studies either compared oxycodone in various formulations or compared oxycodone to different alternative opioids. None found any clear superiority or inferiority of oxycodone for cancer pain, neither as an analgesic agent nor in terms of adverse event rates and treatment acceptability. The certainty of this evidence base was limited by the high or unclear risk of bias of the studies and by imprecision due to low or very low event rates or participant numbers for many outcomes.

AUTHORS' CONCLUSIONS

The conclusions have not changed since the previous version of this review (in 2017). We found low-certainty evidence that there may be little to no difference in pain intensity, pain relief and adverse events between oxycodone and other strong opioids including morphine, commonly considered the gold standard strong opioid. Although we identified a benefit for pain relief in favour of CR morphine over CR oxycodone, this was not clinically significant and did not persist following sensitivity analysis and so we do not consider this important. However, we found that constipation and hallucinations occurred less often with CR oxycodone than with CR morphine; but the certainty of this evidence was either very low or the finding did not persist following sensitivity analysis, so these findings should be treated with utmost caution. Our conclusions are consistent with other reviews and suggest that, while the reliability of the evidence base is low, given the absence of important differences within this analysis, it seems unlikely that larger head-to-head studies of oxycodone versus morphine are justified, although well-designed trials comparing oxycodone to other strong analgesics may well be useful. For clinical purposes, oxycodone or morphine can be used as first-line oral opioids for relief of cancer pain in adults.

Oxycodone in the Opioid Epidemic: High 'Liking', 'Wanting', and Abuse Liability

It is estimated that nearly a third of people who abuse drugs started with prescription opioid medicines. Approximately, 11.5 million Americans used prescription drugs recreationally in 2016, and in 2018, 46,802 Americans died as the result of an opioid overdose, including prescription opioids, heroin, and illicitly manufactured fentanyl (National Institutes on Drug Abuse (2020) Opioid Overdose Crisis. https://www.drugabuse.gov/drugs-abuse/opioids/opioid-overdose-crisis . Accessed 06 June 2020). Yet physicians will continue to prescribe oral opioids for moderate-to-severe pain in the absence of alternative therapeutics, underscoring the importance in understanding how drug choice can influence detrimental outcomes. One of the opioid prescription medications that led to this crisis is oxycodone, where misuse of this drug has been rampant. Being one of the most highly prescribed opioid medications for treating moderate-to-severe pain as reflected in the skyrocketed increase in retail sales of 866% between 1997 and 2007, oxycodone was initially suggested to be less addictive than morphine. The false-claimed non-addictive formulation of oxycodone, OxyContin, further contributed to the opioid crisis. Abuse was often carried out by crushing the pills for immediate burst release, typically by nasal insufflation, or by liquefying the pills for intravenous injection. Here, we review oxycodone pharmacology and abuse liability as well as present the hypothesis that oxycodone may exhibit a unique pharmacology that contributes to its high likability and abuse susceptibility. We will discuss various mechanisms that likely contribute to the high abuse rate of oxycodone including clinical drug likability, pharmacokinetics, pharmacodynamics, differences in its actions within mesolimbic reward circuity compared to other opioids, and the possibility of differential molecular and cellular receptor interactions that contribute to its selective effects. We will also discuss marketing strategies and drug difference that likely contributes to the oxycodone opioid use disorders and addiction.

Drug-Drug Interaction Between Oxycodone and Diazepam by a Combined in Silico Pharmacokinetic and Pharmacodynamic Modeling Approach

Opioids and benzodiazepines have complex drug-drug interactions (DDIs), which serve as an important source of adverse drug effects. In this work, we predicted the DDI between oxycodone (OXY) and diazepam (DZP) in the human body by applying in silico pharmacokinetic (PK) and pharmacodynamic (PD) modeling and simulation. First, we studied the PK interaction between OXY and DZP with a physiologically based pharmacokinetic (PBPK) model. Second, we applied molecular modeling techniques including molecular docking, molecular dynamics (MD) simulation, and the molecular mechanics/Poisson-Boltzmann surface area (MM-PBSA) free energy method to predict the PD-DDI between these two drugs. The PK interaction between OXY and DZP predicted by the PBPK model was not obvious. No significant interaction was observed between the two drugs at normal doses, though very high doses of DZP demonstrated a non-negligible inhibitory effect on OXY metabolism. On the contrary, the molecular modeling study shows that DZP has potential to compete with OXY at the same binding pocket of the active μ-opioid receptor (MOR) and κ-opioid receptor (KOR). MD simulation and MM-PBSA calculation results demonstrated that there is likely a synergetic effect between OXY and DZP binding to opioid receptors, as OXY is likely to target the active MOR while DZP selectively binds to the active KOR. Thus, pharmacokinetics contributes slightly to the DDI between OXY and DZP although an overdose of DZP has been brought to attention. Pharmacodynamics is likely to play a more important role than pharmacokinetics in revealing the mechanism of DDI between OXY and DZP.

Effect of intravenous oxycodone on the physiologic responses to extubation following general anesthesia

BACKGROUND

Endotracheal intubation and extubation may cause undesirable hemodynamic changes. Intravenous oxycodone has recently been introduced and used for relieving hemodynamic alterations in response to intubation, but there is insufficient information regarding its application in stabilizing hemodynamics during extubation in the patients emerging from general anesthesia.

METHODS

One hundred patients, who had undergone assorted laparoscopic surgeries under general anesthesia, were randomly assigned to Control group (saline injection, 50 cases) and Study group (intravenous injection of 0.08 mg/kg oxycodone immediately after completion of the surgical procedure, 50 cases). Blood pressure, heart rate, blood oxygen saturation (SpO₂) as well as blood concentrations of epinephrine, norepinephrine, and cortisol were recorded or measured immediately before extubation (T₀), during extubation (T₁), as well as one minute (T₂), 5 min (T₃), and 10 min after extubation (T₄). In addition, coughing and restlessness, time of eye-opening, and duration from completing surgery to extubation as well as Ramsay Sedation Scale were analyzed.

RESULTS

Blood pressure and heart rate as well as blood concentrations of epinephrine, norepinephrine, and cortisol were significantly higher in the Control group compared with the Study group at the time of extubation as well as 1, 5, and 10 min after extubation (P < 0.05). When the patients emerged from general anesthesia, 70 % of the Control group had cough, which was significantly higher than that of Study group (40 %, P < 0.05). Significantly higher number of patients manifested restlessness in the Control group before (40 %) and after extubation (20 %) compared with that in the Study group (20 and 2 %, respectively, P < 0.05). In addition, patients of Control group had lower Ramsay score at extubation (1.7 ± 0.7) as well as 30 min after extubation (2.4 ± 0.9) compared to that of the patients of Study group (2.2 ± 0.9, and 3.0 ± 0.8, respectively, P = 0.003 and 0.001).

CONCLUSIONS

Intravenous oxycodone attenuated alterations of hemodynamics and blood hormones associated with extubation during emergence from general anesthesia.

TRIAL REGISTRATION

Chinese Clinical Trial Registry: ChiCTR2000040370 (registration date: 11-28-2020) "'retrospectively registered".

Feasibility of using oxycodone as the sole opioid for induction and maintenance of general anaesthesia in minor/moderate surgery: a prospective, observational, descriptive study

Objectives

This study presented the feasibility of oxycodone as the sole opioid for general anaesthesia in minor/moderate surgery.

Methods

In this prospective, observational, descriptive study, 62 patients were enrolled and received intravenous oxycodone as the sole opioid for the induction and maintenance of general anaesthesia. We observed all of these patients to determine whether oxycodone alone could provide sufficient intraoperative and postoperative analgesia, as well as to record the extubation times and adverse events.

Results

A total oxycodone dose of 0.316 ± 0.05 mg/kg was used for induction and maintenance of general anaesthesia. The dose could maintain haemodynamic stability during surgery and good postoperative analgesia. Oxycodone caused deep sedation (nine patients had Ramsey sedation scores ≥4), leading to respiratory depression and long stays in the post-anaesthesia care unit (PACU). The extubation time (16.9 ± 6.4 minutes) increased with increasing oxycodone doses.

Conclusion

Oxycodone can be used as the sole opioid for general anaesthesia in minor/moderate surgery. However, care should be taken because of its deep sedation effect.

Trial registration: This study is registered at the Chinese Clinical Trial Registry (www.chictr.org.cn): ChiCTR-opc-16009175

Prolonged Withdrawal From Escalated Oxycodone Is Associated With Increased Expression of Glutamate Receptors in the Rat Hippocampus

People suffering from opioid use disorder (OUD) exhibit cognitive dysfunctions. Here, we investigated potential changes in the expression of glutamate receptors in rat hippocampi at 2 h and 31 days after the last session of oxycodone self-administration (SA). RNA extracted from the hippocampus was used in quantitative polymerase chain reaction analyses. Rats, given long-access (9 h per day) to oxycodone (LgA), took significantly more drug than rats exposed to short-access (3 h per day) (ShA). In addition, LgA rats could be further divided into higher oxycodone taking (LgA-H) or lower oxycodone taking (LgA-L) groups, based on a cut-off of 50 infusions per day. LgA rats, but not ShA, rats exhibited incubation of oxycodone craving. In addition, LgA rats showed increased mRNA expression of GluA1-3 and GluN2a-c subunits as well as Grm3, Grm5, Grm6, and Grm8 subtypes of glutamate receptors after 31 days but not after 2 h of stopping the SA experiment. Changes in GluA1-3, Grm6, and Grm8 mRNA levels also correlated with increased lever pressing (incubation) after long periods of withdrawal from oxycodone. More studies are needed to elucidate the molecular mechanisms involved in altering the expression of these receptors during withdrawal from oxycodone and/or incubation of drug seeking.

Structural elucidation and synthesis of a dimeric degradation impurity during long-term stability studies of oxycodone hydrochloride injection

An unknown degradation product (impurity-I) observed in oxycodone hydrochloride injection was proposed as an oxycodone aldol dimer using 2D LC-QTOF MS/MS, and impurity-I was synthesized and verified by 1D-NMR and 2D-NMR spectroscopy techniques.

Prescribing Prevalence of Medications With Potential Genotype-Guided Dosing in Pediatric Patients

IMPORTANCE

Genotype-guided prescribing in pediatrics could prevent adverse drug reactions and improve therapeutic response. Clinical pharmacogenetic implementation guidelines are available for many medications commonly prescribed to children. Frequencies of medication prescription and actionable genotypes (genotypes where a prescribing change may be indicated) inform the potential value of pharmacogenetic implementation.

OBJECTIVE

To assess potential opportunities for genotype-guided prescribing in pediatric populations among multiple health systems by examining the prevalence of prescriptions for each drug with the highest level of evidence (Clinical Pharmacogenetics Implementation Consortium level A) and estimating the prevalence of potential actionable prescribing decisions.

DESIGN, SETTING, AND PARTICIPANTS

This serial cross-sectional study of prescribing prevalences in 16 health systems included electronic health records data from pediatric inpatient and outpatient encounters from January 1, 2011, to December 31, 2017. The health systems included academic medical centers with free-standing children's hospitals and community hospitals that were part of an adult health care system. Participants included approximately 2.9 million patients younger than 21 years observed per year. Data were analyzed from June 5, 2018, to April 14, 2020.

EXPOSURES

Prescription of 38 level A medications based on electronic health records.

MAIN OUTCOMES AND MEASURES

Annual prevalence of level A medication prescribing and estimated actionable exposures, calculated by combining estimated site-year prevalences across sites with each site weighted equally.

RESULTS

Data from approximately 2.9 million pediatric patients (median age, 8 [interquartile range, 2-16] years; 50.7% female, 62.3% White) were analyzed for a typical calendar year. The annual prescribing prevalence of at least 1 level A drug ranged from 7987 to 10 629 per 100 000 patients with increasing trends from 2011 to 2014. The most prescribed level A drug was the antiemetic ondansetron (annual prevalence of exposure, 8107 [95% CI, 8077-8137] per 100 000 children). Among commonly prescribed opioids, annual prevalence per 100 000 patients was 295 (95% CI, 273-317) for tramadol, 571 (95% CI, 557-586) for codeine, and 2116 (95% CI, 2097-2135) for oxycodone. The antidepressants citalopram, escitalopram, and amitriptyline were also commonly prescribed (annual prevalence, approximately 250 per 100 000 patients for each). Estimated prevalences of actionable exposures were highest for oxycodone and ondansetron (>300 per 100 000 patients annually). CYP2D6 and CYP2C19 substrates were more frequently prescribed than medications influenced by other genes.

CONCLUSIONS AND RELEVANCE

These findings suggest that opportunities for pharmacogenetic implementation among pediatric patients in the US are abundant. As expected, the greatest opportunity exists with implementing CYP2D6 and CYP2C19 pharmacogenetic guidance for commonly prescribed antiemetics, analgesics, and antidepressants.

The Role of Opioids in Pain Management in Elderly Patients with Chronic Kidney Disease: A Review Article

Chronic kidney disease (CKD) is a global public health problem. Pain is one of the most generally experienced symptoms by CKD patients. Pain management is a key clinical activity; nonetheless, insufficient pain management by health professionals keeps it up. Opioids as pain relievers are a class of naturally-derived and synthetic medications. They act through interactions with receptors in peripheral nerves. Numerous pharmacokinetic alterations happen with aging that influence drug disposition, metabolism, and quality of life. Acetaminophen alone, or combined with low-potency opioid dose is regarded as the safest pain-relieving choice for CKD. Morphine and codeine are probably eluded in renal impairment patients and used with excessive carefulness. Tramadol, oxycodone, and hydromorphone can be used by patient monitoring, while methadone, transdermal fentanyl, and buprenorphine seem to be safe to use in older non-dialysis patients with renal impairment. Consistent with the available literature, the main aim of this review was to explore the occurrence of chronic pain and its opioid treatment in CKD patients. According to this review, more and well-made randomized controlled trials are necessary to find appropriate opioid doses and explore the occurrence of side effects.

Organophotocatalytic N-Demethylation of Oxycodone Using Molecular Oxygen

N‐Demethylation of oxycodone is one of the key steps in the synthesis of important opioid antagonists like naloxone or analgesics like nalbuphine. The reaction is typically carried out using stoichiometric amounts of toxic and corrosive reagents. Herein, we present a green and scalable organophotocatalytic procedure that accomplishes the N‐demethylation step using molecular oxygen as the terminal oxidant and an organic dye (rose bengal) as an effective photocatalyst. Optimization of the reaction conditions under continuous flow conditions using visible‐light irradiation led to an efficient, reliable, and scalable process, producing noroxycodone hydrochloride in high isolated yield and purity after a simple workup.

Once-Daily Oxycodone Prolonged-Release Tablets Are Resistant to Alcohol-Induced Dose Dumping: Results From a Randomized Trial in Healthy Volunteers

The objective of this study was to determine the effect of concomitant alcohol intake on the bioavailability of oxycodone from an oxycodone once-daily (OOD) formulation and an oxycodone twice-daily (OTD) formulation. A phase I, open-label, randomized, crossover alcohol interaction study in 20 healthy volunteers under fasting conditions was conducted. Participants received five treatments, OOD with 240 mL of 0%, 20%, or 40% alcohol; and OTD with 240 mL of 0% or 40% alcohol. Pharmacokinetic parameters did not differ between participants taking OOD with water or with 240 mL of 20% alcohol. There was a slight increase in overall oxycodone absorption from OOD with 40% alcohol but no increase in peak absorption. Oxycodone absorption from OTD showed peak and overall increases with 40% alcohol but maintained a prolonged-release profile. Although it is recommended that alcohol be avoided while taking opioids, there was no evidence of alcohol-induced dose dumping in these oxycodone formulations.

Role of Oxycodone Hydrochloride in Treating Radiotherapy-Related Pain

Radiotherapy is commonly used to treat cancer patients. Besides the curable effect, radiotherapy also could relieve the pain of cancer patients. However, cancer pain is gradually alleviated about two weeks after radiotherapy. In addition, cancer patients who receive radiotherapy may also suffer from pain flare or radiotherapy-induced side effects such as radiation esophagitis, enteritis, and mucositis. Pain control is reported to be inadequate during the whole course of radiotherapy (before, during, and after radiotherapy), and quality of life is seriously affected. Hence, radiotherapy is suggested to be combined with analgesic drugs in clinical guidelines. Previous studies have shown that radiotherapy combined with oxycodone hydrochloride can effectively alleviate cancer pain. In this review, we firstly presented the necessity of analgesia during the whole course of radiotherapy. We also sketched the role of oxycodone hydrochloride in radiotherapy of bone metastases and radiotherapy-induced oral mucositis. Finally, we concluded that oxycodone hydrochloride shows good efficacy and tolerance and could be used for pain management before, during, and after radiotherapy.

Effects of oxycodone on sensitivity to reinforcement magnitude: implications for effects of opioids on impulsive and risky choice

Opioid addiction/dependence is associated with impulsive and risky behavior. Moreover, opioids can increase impulsive choice in preclinical studies with nonhumans. The objective of this study was to investigate a potential behavioral mechanism of opioids: a change in the impact of reinforcement magnitude on choice. Rats (n = 7) chose between smaller and larger reinforcers under a continuous-choice (concurrent-chains) procedure. The levers associated with the smaller and larger reinforcers alternated every five sessions. During baseline under this procedure, rats showed a reliable preference for the larger reinforcer. Effects of several doses (0.1-1.7 mg/kg, s.c.) of the prescription opioid, oxycodone, were examined on preference based upon reinforcement magnitude. Oxycodone dose-dependently decreased preference for the larger reinforcer (i.e. decreased sensitivity to reinforcement magnitude). The decrease in sensitivity to reinforcement magnitude was selective in that the intermediate doses did not affect, or had minimal impact on, other measures of performance (e.g. on general motivation to respond). These data suggest that a decrease in the sensitivity to reinforcement magnitude is a reliable outcome of μ-opioid administration, an effect that has important implications for the impact of these drugs on both impulsive and risky behavior.

Pharmacokinetics and Bioequivalence Evaluation of a New Oxycodone Tamper-Resistant Tablet Administered with an Opioid Antagonist in Patients with Chronic Pain

BACKGROUND AND OBJECTIVES

Oxycodone tamper resistant (OTR) is a new extended-release abuse-deterrent formulation providing improvements in the tamper resistant characteristics. This study aimed to investigate the pharmacokinetic properties of the new OTR tablets and evaluate the bioequivalence of oxycodone from OTR and the original extended release (ER) formulation tablets administered with an opioid antagonist in patients with chronic pain.

METHODS

In this open-label, randomized, cross-over study, the enrolled patients were randomised to receive a single dose of 40 mg OTR or 40 mg OXYCONTIN^® (OXY) tablet administered with naltrexone blockade under fasting conditions. Serial blood samples for pharmacokinetic analysis were collected. Plasma oxycodone was quantified by a high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method. Tolerability was evaluated by monitoring adverse events, physical examinations, 12-lead ECG and laboratory tests.

RESULTS

A total of 38 patients were enrolled and 33 subjects completed the study. After a single dose of 40 mg tablets, pharmacokinetic results of the new OTR tablet were found to be similar to those of original extended-release oxycodone tablet. OTR 40 mg was bioequivalent to OXY 40 mg and was well tolerated in patients with chronic pain.

CONCLUSIONS

The new OTR formulation could provide a new choice in the treatment of chronic pain and reduce the potential for oxycodone abuse. Chictr.org identifier: ChiCTR1800017253.

Escalated Oxycodone Self-Administration Causes Differential Striatal mRNA Expression of FGFs and IEGs Following Abstinence-Associated Incubation of Oxycodone Craving

Addiction to prescribed opioids including oxycodone has reached tragic levels. Herein, we investigated the relevance of fibroblast growth factors (FGFs) and immediate early genes (IEGs) to withdrawal-induced incubation of drug craving following escalated oxycodone self-administration (SA). Rats were trained to self-administer oxycodone for 4 weeks. Seeking tests were performed at various intervals during 1 month of drug withdrawal. Rats were euthanized 1 day after the last test and nucleus accumbens and dorsal striata were dissected for use in PCR analyses. Rats given long access (LgA, 9 h), but not short access (ShA, 3 h) to drug escalated their oxycodone intake and exhibited incubation of oxycodone seeking during withdrawal. These rats exhibited dose-dependent increases in fgf2 expression in the dorsal striatum. Fgfr2 expression was also significantly increased in the striatum in LgA, but not ShA groups. Similarly, striatal c-fos and junB mRNA levels showed greater increases in LgA rats. The observations that fgf mRNA levels were more altered in the dorsal striatum than in the NAc of LgA rats suggest that changes in striatal FGF expression may be more salient to incubation of oxycodone craving than alterations in the NAc. Targeting FGF signaling pathways might offer novel strategies against opioid addiction.

Rat brain CYP2D activity alters in vivo central oxycodone metabolism, levels and resulting analgesia

Oxycodone is metabolized by CYP2D to oxymorphone. Despite oxymorphone being a more potent opioid-receptor agonist, its contribution to oxycodone analgesia may be minor because of low peripheral production, low blood-brain barrier permeability and central nervous system efflux. CYP2D metabolism within the brain may contribute to variation in central oxycodone and oxymorphone levels, thereby affecting analgesia. Brain CYP2D expression and activity are subject to exogenous regulation; nicotine induces rat brain, but not liver, CYP2D consistent with higher brain CYP2D in smokers. We assessed the role of rat brain CYP2D in orally administered oxycodone metabolism (in vivo brain microdialysis) and analgesia (tail-flick test) by inhibiting brain CYP2D selectively with intracerebroventricular propranolol (mechanism-based inhibitor) and inducing brain CYP2D with nicotine. Inhibiting brain CYP2D increased brain oxycodone levels (1.8-fold; P < 0.03) and analgesia (1.5-fold AUC_0-60 ; P < 0.001) after oxycodone, while inducing brain CYP2D increased brain oxymorphone levels (4.6-fold; P < 0.001) and decreased analgesia (0.8-fold; P < 0.02). Inhibiting the induced brain CYP2D reversed the change in oxycodone levels (1.2-fold; P > 0.1) and analgesia (1.1-fold; P > 0.3). Brain, but not plasma, metabolic ratios were affected by pre-treatments. Peak analgesia was inversely correlated with ex vivo brain (P < 0.003), but not hepatic (P > 0.9), CYP2D activity. Altering brain CYP2D did not affect analgesia from oral oxymorphone (P > 0.9 for AUC_0-60 across all groups), which is not a CYP2D substrate. Thus, brain CYP2D metabolism alters local oxycodone levels and response, suggesting that people with increased brain CYP2D activity may have reduced oxycodone response. Factors that alter individual oxycodone response may be useful for optimizing treatment and minimizing abuse liability.

The role of oxycodone/naloxone in the management of patients with pain and opioid-induced constipation

INTRODUCTION

Common opioid adverse effects (AE) of the gastrointestinal tract include opioid-induced constipation (OIC) and opioid-induced bowel dysfunction (OIBD) with traditional laxatives being of limited efficacy, having AEs and not addressing the pathophysiology of OIC or OIBD. Targeted treatment comprises of PAMORA (peripherally acting mu-opioid receptor antagonists) and a combination of an opioid receptor agonist with its antagonist, namely prolonged-release oxycodone with prolonged-release naloxone (OXN) tablets at a fixed ratio of 2:1. Oxycodone provides analgesia, whereas naloxone prevents binding or displaces it from opioid receptors located in the gut wall. Areas covered: The authors review the role of OXN in the management of patients with pain and OIC. A literature search was performed using the search terms 'oxycodone/naloxone' and 'opioid-induced constipation' using the PubMed database up to October 2018. Expert opinion: OXN delivers analgesia comparable (or superior versus placebo and in observational studies) to oxycodone alone and other opioids with a limited or decreased disturbing effect on bowel function. OXN in daily doses of up to 160 mg/80 mg provides effective analgesia with little negative impact on bowel function. OXN may be successfully used in patients with chronic pain, to prevent or treat symptoms of OIC and OIBD.

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.

Oral prolonged-release oxycodone/naloxone offers equivalent analgesia to intravenous morphine patient-controlled analgesia after total knee replacement. A randomized controlled trial

BACKGROUND

The purpose of this study was to determine whether oral prolonged-release oxycodone-naloxone combination (OXN) could provide equivalent analgesia and a side-effect profile similar to intravenous morphine patient-controlled analgesia (IVPCA) for the control of pain in the immediate postoperative period after total knee replacement (TKR).

METHODS

All patients received a sciatic nerve block with 0.3% ropivacaine 15 mL, femoral nerve block with 0.5% ropivacaine 20 mL, spinal anesthesia and postoperative continuous femoral nerve infusion (ropivacaine 0.2% 4 mL/h). After surgery, patients were randomly allocated to receive either 10 +10 +5 mg controlled release OXN oral administration 12 hourly or IVPCA with morphine (2 mg bolus, no basal infusion). The primary outcome was the average rest and dynamic pain for the first 48 h postoperatively. Secondary outcomes were: post operative nausea vomiting (PONV) and the total morphine consumption.

RESULTS

OXN group experienced better pain control at rest during the first (0.89±1.54 vs. 1.27±1.82, P=0.0019) and second (1.03±1.69 vs. 1.65±2.05, P=0.0006) postoperative period. There was no statistically significant difference in pain score during movement between the two groups. The secondary outcome measures showed no significant differences in the total morphine consumption (12.04±1.1 vs. 11.46±3.7 mg, P=0.20) or PONV (0.6±0.8 vs. 0.8±1.0, P=0.40).

CONCLUSIONS

This study show that in the immediate postoperative period after TKR, the patients receiving oral prolonged-release OXN experienced the same to better pain control than those receiving morphine IVPCA, with a similar degree of PONV.

Bioavailability of oxycodone after administration of a new prolonged-release once-daily tablet formulation in healthy subjects, in comparison to an established twice-daily tablet

OBJECTIVE

To evaluate and to compare the bioavailability, the influence of food intake on the bioavailability, and the safety and tolerability of a newly-developed oxycodone once-daily (OOD) prolonged-release tablet with an established oxycodone twice-daily (OTD) prolonged-release tablet after single-dose administration under fasting or fed conditions as well as after multiple-dose administration.

MATERIALS AND METHODS

Three single-center, open-label, randomized, balanced, two-treatment, two-period, two-sequence crossover studies were conducted. In each study, 36 healthy volunteers were randomized to receive 10 mg oxycodone daily as OOD (oxycodone HCL 10-mg PR tablets XL (Develco Pharma Schweiz AG, Pratteln, Switzerland); administration of 1 tablet in the morning) or as OTD (reference formulation: oxygesic 5-mg tablets (Mundipharma GmbH, Limburg an der Lahn, Germany); administration of 1 tablet in the morning and 1 tablet in the evening). Tablets were administered once daily or twice daily under fasting conditions (study 1) or under fed conditions (study 2) as well as after multiple-dose administration (study 3). A sufficient number of blood samples were taken for describing plasma profiles and for calculation of pharmacokinetic parameters. Plasma concentrations of oxycodone were determined by LC-MS/MS. Safety and tolerability were monitored and assessed in all three studies.

RESULTS

Plasma profiles of OOD reveal sustained concentrations of oxycodone over the complete dosing interval of 24 hours. In comparison to the OTD reference formulation, the OOD test formulation showed a slightly slower increase of concentrations within the absorption phase and similar plasma concentrations at the maximum and at the end of the dosing interval (24 hours). Extent of bioavailability (AUC), maximum plasma concentrations (C_max), and plasma concentrations at the end of the dosing interval (C_τ,ss,24h) of OOD could be classified as comparable to OTD considering 90% confidence intervals (CIs) and acceptance limits of 80.00 - 125.00%. Bioavailability of OOD was not influenced by concomitant food intake. OOD and OTD were generally well tolerated, a difference between the two products could not be observed.

CONCLUSION

The new 10-mg OOD formulation provides sustained oxycodone plasma concentrations over the dosing interval of 24 hours and is suitable for once-daily administration. Bioavailability of OOD could be classified as comparable to the twice-daily administration of the OTD reference formulation. The new formulation widens and optimizes the range of strong opioid drug products in patient-centered therapy of chronic pain with simplified dosing and better compliance.
.

Pharmacokinetic Bioequivalence Studies of an Extended-Release Oxycodone Hydrochloride Tablet in Healthy Japanese Subjects Under Fasting and Fed Conditions Without an Opioid Antagonist

Oxycodone is a semisynthetic opioid used for the treatment of moderate to severe pain. Two separate studies were conducted to assess the pharmacokinetic bioequivalence of a newly formulated oxycodone hydrochloride extended-release tablet to a marketed oxycodone product in Japan under fasting and fed conditions. Each study was a randomized, open-label, single-dose, single-center, two-period, two-way crossover study. Healthy male Japanese subjects received the oxycodone 10-mg products under fasting and fed conditions. Blood samples were collected at specified time intervals, and plasma concentrations of oxycodone were analyzed using a validated liquid chromatography tandem mass spectrometry assay method. The pharmacokinetic parameters were determined via non-compartmental analysis. Pharmacokinetic metrics used for bioequivalence assessment were the maximum observed plasma concentration (C max) and the area under the concentration-time curve up to the last sampling time (AUC t ). A total of 24 healthy subjects were enrolled in each study. One subject withdrew after completion of the first sequence under fed conditions. The ratios of geometric least square means for C max and AUC t under fasting conditions were 1.1110 (90% confidence interval [CI] 1.0562-1.1687) and 0.9946 (90% CI 0.9670-1.0231), respectively. The ratios of geometric least square means for C max and AUCt under fed conditions were 1.1417 (90% CI 1.0959-1.1895) and 1.0135 (90% CI 0.9810-1.0470), respectively. The 90% CIs were within the predefined range (0.80-1.25). Both treatments were well tolerated when taken without an opioid antagonist in healthy Japanese subjects. Pharmacokinetic bioequivalence between test and reference formulations under fasting and fed conditions was concluded in terms of both rate and extent of absorption.

Pharmacokinetics, safety and tolerability of a novel tocopheryl phosphate mixture/oxycodone transdermal patch system: a Phase I study

AIM

To characterize the pharmacokinetic profile and evaluate the safety and tolerability of a transdermal oxycodone patch containing tocopheryl phosphate mixture (TPM).

PATIENTS & METHODS

Eleven healthy subjects received a single application of three TPM/oxycodone patches applied to the torso for 72 h.

RESULTS

Oxycodone was detected 8.0 ± 2.7-h postpatch administration, reaching a mean maximum plasma concentration of 3.41 ± 1.34 ng/ml at 49.3 ± 21.2 h. The safety profile was consistent with the application method and known side-effect profile of oxycodone and naltrexone. No treatment-limiting skin irritation was observed.

CONCLUSION

A 3-day application of the TPM/oxycodone patch demonstrated an acceptable safety profile and was well tolerated by healthy subjects, with limited dermal irritation following application.

Efficacy and tolerability balance of oxycodone/naloxone and tapentadol in chronic low back pain with a neuropathic component: a blinded end point analysis of randomly selected routine data from 12-week prospective open-label observations

Objective

To evaluate the benefit–risk profile (BRP) of oxycodone/naloxone (OXN) and tapentadol (TAP) in patients with chronic low back pain (cLBP) with a neuropathic component (NC) in routine clinical practice.

Methods

This was a blinded end point analysis of randomly selected 12-week routine/open-label data of the German Pain Registry on adult patients with cLBP-NC who initiated an index treatment in compliance with the current German prescribing information between 1st January and 31st October 2015 (OXN/TAP, n=128/133). Primary end point was defined as a composite of three efficacy components (≥30% improvement of pain, pain-related disability, and quality of life each at the end of observation vs baseline) and three tolerability components (normal bowel function, absence of either central nervous system side effects, and treatment-emergent adverse event [TEAE]-related treatment discontinuation during the observation period) adopted to reflect BRP assessments under real-life conditions.

Results

Demographic as well as baseline and pretreatment characteristics were comparable for the randomly selected data sets of both index groups without any indicators for critical selection biases. Treatment with OXN resulted formally in a BRP noninferior to that of TAP and showed a significantly higher primary end point response vs TAP (39.8% vs 25.6%, odds ratio: 1.93; P=0.014), due to superior analgesic effects. Between-group differences increased with stricter response definitions for all three efficacy components in favor of OXN: ≥30%/≥50%/≥70% response rates for OXN vs TAP were seen for pain intensity in 85.2%/67.2%/39.1% vs 83.5%/54.1%/15.8% (P= ns/0.031/<0.001), for pain-related disability in 78.1%/64.8%/43.8% vs 66.9%/50.4%/24.8% (P=0.043/0.018/0.001), and for quality of life in 76.6%/68.0%/50.0% vs 63.9%/54.1%/34.6% (P=0.026/0.022/0.017). Overall, OXN vs TAP treatments were well tolerated, and proportions of patients who either maintained a normal bowel function (68.0% vs 72.2%), reported no central nervous system side effects (91.4% vs 89.5%), or completed the 12-week evaluation period without any TEAE-related treatment discontinuations (93.0% vs 92.5%) were similar for both index medications (P= ns for each comparison).

Conclusion

In daily practice, the BRP of OXN proved to be noninferior to that of TAP in patients with cLBP-NC, but showed a superior efficacy if stricter analgesic response definitions were evaluated.

Drugs of abuse and addiction: A slippery slope toward liver injury

Substances of abuse induce alteration in neurobehavioral symptoms, which can lead to simultaneous exacerbation of liver injury. The biochemical changes of liver are significantly observed in the abused group of people using illicit drugs or drugs that are abused. A huge amount of work has been carried out by scientists for validation experiments using animal models to assess hepatotoxicity in cases of drugs of abuse. The risk of hepatotoxicity from these psychostimulants has been determined by different research groups. Hepatotoxicity of these drugs has been recently highlighted and isolated case reports always have been documented in relation to misuse of the drugs. These drugs induce liver toxicity on acute or chronic dose dependent process, which ultimately lead to liver damage, acute fatty infiltration, cholestatic jaundice, liver granulomas, hepatitis, liver cirrhosis etc. Considering the importance of drug-induced hepatotoxicity as a major cause of liver damage, this review emphasizes on various drugs of abuse and addiction which induce hepatotoxicity along with their mechanism of liver damage in clinical aspect as well as in vitro and in vivo approach. However, the mechanisms of drug-induced hepatotoxicity is dependent on reactive metabolite formation via metabolism, modification of covalent bonding between cellular components with drug and its metabolites, reactive oxygen species generation inside and outside of hepatocytes, activation of signal transduction pathways that alter cell death or survival mechanism, and cellular mitochondrial damage, which leads to alteration in ATP generation have been notified here. Moreover, how the cytokines are modulated by these drugs has been mentioned here.

Developments in managing severe chronic pain: role of oxycodone-naloxone extended release

Chronic pain is a highly disabling condition, which can significantly reduce patients’ quality of life. Prevalence of moderate and severe chronic pain is high in the general population, and it increases significantly in patients with advanced cancer and older than 65 years. Guidelines for the management of chronic pain recommend opioids for the treatment of moderate-to-severe pain in patients whose pain is not responsive to initial therapies with paracetamol and/or nonsteroidal anti-inflammatory drugs. Despite their analgesic efficacy being well recognized, adverse events can affect daily functioning and patient quality of life. Opioid-induced constipation (OIC) occurs in 40% of opioid-treated patients. Laxatives are the most common drugs used to prevent and treat OIC. Laxatives do not address the underlying mechanisms of OIC; for this reason, they are not really effective in OIC treatment. Naloxone is an opioid receptor antagonist with low systemic bioavailability. When administered orally, naloxone antagonizes the opioid receptors in the gut wall, while its extensive first-pass hepatic metabolism ensures the lack of antagonist influence on the central-mediated analgesic effect of the opioids. A prolonged-release formulation consisting of oxycodone and naloxone in a 2:1 ratio was developed trying to reduce the incidence of OIC maintaining the analgesic effect compared with use of the sole oxycodone. This review includes evidence related to use of oxycodone and naloxone in the long-term management of chronic non-cancer pain and OIC.

Treatment of failed back surgery syndrome in a forty-three-year-old man with high-dose oxycodone/naloxone

Introduction:

Failed back surgery syndrome (FBSS) is an increasing cause of chronic pain in most countries. This poses high costs to both patients and National Health Organizations.

Case Presentation:

In this report, multimodal pain management based on daily high-dose oxycodone/naloxone (OXN 180/90 mg) led to reduced patient's pain score and improved quality of life.

Conclusions:

Oxycodone/naloxone can be a good alternative for the management of FBSS when other interventional or pharmacologic strategies have failed. In this case report, higher doses than those recommended as a maximum daily ceiling (80/40 mg) were safely used in one selected patient with noncancer severe pain.

Emerging therapies for patients with symptoms of opioid-induced bowel dysfunction

Opioid-induced bowel dysfunction (OIBD) comprises gastrointestinal (GI) symptoms, including dry mouth, nausea, vomiting, gastric stasis, bloating, abdominal pain, and opioid-induced constipation, which significantly impair patients’ quality of life and may lead to undertreatment of pain. Traditional laxatives are often prescribed for OIBD symptoms, although they display limited efficacy and exert adverse effects. Other strategies include prokinetics and change of opioids or their administration route. However, these approaches do not address underlying causes of OIBD associated with opioid effects on mostly peripheral opioid receptors located in the GI tract. Targeted management of OIBD comprises purely peripherally acting opioid receptor antagonists and a combination of opioid receptor agonist and antagonist. Methylnaltrexone induces laxation in 50%–60% of patients with advanced diseases and OIBD who do not respond to traditional oral laxatives without inducing opioid withdrawal symptoms with similar response (45%–50%) after an oral administration of naloxegol. A combination of prolonged-release oxycodone with prolonged-release naloxone (OXN) in one tablet (a ratio of 2:1) provides analgesia with limited negative effect on the bowel function, as oxycodone displays high oral bioavailability and naloxone demonstrates local antagonist effect on opioid receptors in the GI tract and is totally inactivated in the liver. OXN in daily doses of up to 80 mg/40 mg provides equally effective analgesia with improved bowel function compared to oxycodone administered alone in patients with chronic non-malignant and cancer-related pain. OIBD is a common complication of long-term opioid therapy and may lead to quality of life deterioration and undertreatment of pain. Thus, a complex assessment and management that addresses underlying causes and patomechanisms of OIBD is recommended. Newer strategies comprise methylnaltrexone or OXN administration in the management of OIBD, and OXN may be also considered as a preventive measure of OIBD development in patients who require opioid administration.

Treatment with prolonged-release oxycodone/naloxone improves pain relief and opioid-induced constipation compared with prolonged-release oxycodone in patients with chronic severe pain and laxative-refractory constipation

PURPOSE

Laxative-refractory opioid-induced constipation (OIC) is defined as OIC despite using 2 laxatives with a different mechanism of action (based on the Anatomical Therapeutic Chemical Classification System level 4 term [contact laxatives, osmotically acting laxatives, softeners/emollients, enemas, and others]). OIC has a significant impact on the treatment and quality of life of patients with severe chronic pain. This noninterventional, observational, real-life study in Belgium investigated the efficacy of prolonged-release oxycodone/naloxone combination (PR OXN) treatment regarding pain relief and OIC compared with previous prolonged-release oxycodone (PR OXY) treatment for laxative-refractory OIC in daily clinical practice.

METHODS

Laxative-refractory OIC patients with severe chronic pain were treated with PR OXN for 12 weeks (3 visits). Pain relief (assessed on a numerical rating scale) and OIC (assessed by using the Bowel Function Index [BFI]) were evaluated at each visit. A responder was defined as a patient who had: (1) no worsening of pain at the last visit compared with visit 1 or a numerical rating scale ≤4 at visit 3/last visit; and (2) a reduction in BFI ≥12 units at visit 3/last visit compared with visit 1; or (3) a BFI ≤28.8 at visit 3/last visit.

FINDINGS

Sixty-eight laxative-refractory OIC patients with severe chronic pain (mean (sd) age 59.8 (13.3) years, 67.6% female and 91.2% non-malignant pain) were treated for 91 days with PR OXN (median daily dose, 20 mg). Treatment with PR OXN resulted in a significant and clinically relevant decrease of pain of 2.1 units (P < 0.001; 95% CI, 1.66-2.54) and of BFI by 48.5 units (P < 0.001; 95% CI, 44.4-52.7) compared with PR OXY treatment; use of laxatives was also significantly reduced (P < 0.001). Approximately 95% of patients were responders, and quality of life (as measured by using the EQ-5D) improved significantly. Adverse events were opioid related, and PR OXN treatment was well tolerated.

IMPLICATIONS

Treatment with PR OXN resulted in a significant and clinically relevant reduction in OIC compared with previous PR OXY treatment for these patients with severe chronic pain and laxative-refractory OIC. Treatment with PR OXN also resulted in a significant improvement in pain relief and quality of life. ClinicalTrials.gov identifier: NCT01710917.

Prediction of Metabolic Interactions With Oxycodone via CYP2D6 and CYP3A Inhibition Using a Physiologically Based Pharmacokinetic Model

Evaluation of a potential risk of metabolic drug–drug interactions (DDI) is of high importance in the clinical setting. In this study, a physiologically based pharmacokinetic (PBPK) model was developed for oxycodone and its two primary metabolites, oxymorphone and noroxycodone, in order to assess different DDI scenarios using published in vitro and in vivo data. Once developed and refined, the model was able to simulate pharmacokinetics of the three compounds and the DDI extent in case of coadministration with an inhibitor, as well as the oxymorphone concentration variation between CYP2D6 extensive metabolizers (EM) and poor metabolizers (PM). The reliability of the model was tested against published clinical studies monitoring different inhibitors and dose regimens, and all predicted area under the concentration–time curve (AUC) ratios were within the twofold acceptance range. This approach represents a strategy to evaluate the impact of coadministration of different CYP inhibitors using mechanistic incorporation of drug-dependent and system-dependent available in vitro and in vivo data.

Pain Management in Post-Craniotomy Patients: A Survey of Canadian Neurosurgeons

Introduction:

Despite the growing recognition for analgesic needs in post-craniotomy patients, this remains a poorly studied area in neurological surgery. The class and regimen of analgesia that is most suitable for these patients remains controversial. The objective of this study is to examine the current beliefs and practices of Canadian neurosurgeons when managing post-craniotomy pain.

Methods:

A survey was sent to all practicing Canadian neurosurgeons to examine the following aspects of analgesia in craniotomy patients: type of analgesics used, common side effects encountered, satisfaction with current regimen and the rationale for their practice.

Results:

Of 156 potential respondents, 103 neurosurgeons (66%) completed the survey. Codeine (59%) was the most prescribed firstline analgesic followed by morphine (38%). The use of a second-line opioid was significantly higher among codeine prescribers compared to morphine, 53% compared to 28% (p < 0.001). Nausea, constipation and neurologic depression were reported as common side effects by 76%, 66% and 27% of respondents respectively. Of the respondents, 90% reported a high level of satisfaction with their current choice of analgesia; nonetheless, they predominantly described their practice as personal preference or protocol driven rather than evidence-based.

Conclusions:

Codeine - a weak opioid - is the most common first-line analgesic prescribed to craniotomy patients. This practice is associated with substantially increased reliance on potent opioids for rescue analgesia. Whether novel regimens can provide optimal pain control while minimizing neurologic and gastrointestinal side effects remains to be addressed by future trials.

Opioid switch from low dose of oral oxycodone to transdermal fentanyl matrix patch for patients with stable thoracic malignancy-related pain

BACKGROUND

The effectiveness and safety of switch from oral oxycodone to fentanyl patch is little known. Here, we investigated if early phase opioid switch from low dose of oral oxycodone to transdermal fentanyl matrix patch provided any benefits for patients with thoracic malignancy and stable cancer-related pain.

METHODS

This open-label two-centered prospective study enrolled patients with thoracic malignancy suffering persistent malignancy-related pain with numeric rating scale of pain intensity ≤ 3 which had been controlled by oral oxycodone ≤ 20 mg/day. Eligible patients switched from oral oxycodone to 12.5 μg/h of transdermal fentanyl matrix patch. The dose was allowed to be titrated upwards every 3 day by 25-50%, except for the first increase from 12.5 μg/hr to 25 μg/hr,until achieving adequate pain control. The data on patients' global assessment scores measured on a five-step scale, an 11-point numeric rating scale of pain intensity, the severity of adverse effects using a four-point categorical rating scale, and the Epworth sleepiness scale questionnaire were collected for 15 days.

RESULTS

Forty-nine eligible patients were analyzed. Overall patients' satisfaction score significantly improved from day 1 (2.7 ± 0.9) to day 15 (2.3 ± 0.9) (p < 0.05), and 90% and 78% of patients remained to receive the minimum dose of fentanyl patch on day 8 and 15 from the opioid switch. There was a significant difference in sleepiness throughout the study period, though no difference was detected in pain intensity and other adverse effects.

CONCLUSION

Transdermal fentanyl matrix patch is an alternative analgesic option for a stable cancer pain in patients with thoracic malignancies.

Exploring pharmacological activities and signaling of morphinans substituted in position 6 as potent agonists interacting with the μ opioid receptor

BACKGROUND

Opioid analgesics are the most effective drugs for the treatment of moderate to severe pain. However, they also produce several adverse effects that can complicate pain management. The μ opioid (MOP) receptor, a G protein-coupled receptor, is recognized as the opioid receptor type which primarily mediates the pharmacological actions of clinically used opioid agonists. The morphinan class of analgesics including morphine and oxycodone are of main importance as therapeutically valuable drugs. Though the natural alkaloid morphine contains a C-6-hydroxyl group and the semisynthetic derivative oxycodone has a 6-carbonyl function, chemical approaches have uncovered that functionalizing position 6 gives rise to a range of diverse activities. Hence, position 6 of N-methylmorphinans is one of the most manipulated sites, and is established to play a key role in ligand binding at the MOP receptor, efficacy, signaling, and analgesic potency. We have earlier reported on a chemically innovative modification in oxycodone resulting in novel morphinans with 6-acrylonitrile incorporated substructures.

RESULTS

This study describes in vitro and in vivo pharmacological activities and signaling of new morphinans substituted in position 6 with acrylonitrile and amido functions as potent agonists and antinociceptive agents interacting with MOP receptors. We show that the presence of a 6-cyano group in N-methylmorphinans has a strong influence on the binding to the opioid receptors and post-receptor signaling. One 6-cyano-N-methylmorphinan of the series was identified as the highest affinity and most selective MOP agonist, and very potent in stimulating G protein coupling and intracellular calcium release through the MOP receptor. In vivo, this MOP agonist showed to be greatly effective against thermal and chemical nociception in mice with marked increased antinociceptive potency than the lead molecule oxycodone.

CONCLUSION

Development of such novel chemotypes by targeting position 6 provides valuable insights on ligand-receptor interaction and molecular mode of action, and may aid in identification of opioid therapeutics with enhanced analgesic properties and fewer undesirable effects.