Oxymorphone: a review

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

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

Association of Physical Activity With Bioactive Lipids and Cardiovascular Events

BACKGROUND

To clarify the mechanisms underlying physical activity (PA)-related cardioprotection, we examined the association of PA with plasma bioactive lipids (BALs) and cardiovascular disease (CVD) events. We additionally performed genome-wide associations.

METHODS

PA-bioactive lipid associations were examined in VITAL (VITamin D and OmegA-3 TriaL)-clinical translational science center (REGISTRATION: URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT01169259; N=1032) and validated in JUPITER (Justification for the Use of statins in Prevention: an Intervention Trial Evaluating Rosuvastatin)-NC (REGISTRATION: URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT00239681; N=589), using linear models adjusted for age, sex, race, low-density lipoprotein-cholesterol, total-C, and smoking. Significant BALs were carried over to examine associations with incident CVD in 2 nested CVD case-control studies: VITAL-CVD (741 case-control pairs) and JUPITER-CVD (415 case-control pairs; validation).

RESULTS

We detected 145 PA-bioactive lipid validated associations (false discovery rate <0.1). Annotations were found for 6 of these BALs: 12,13-diHOME, 9,10-diHOME, lysoPC(15:0), oxymorphone-3b-D-glucuronide, cortisone, and oleoyl-glycerol. Genetic analysis within JUPITER-NC showed associations of 32 PA-related BALs with 22 single-nucleotide polymorphisms. From PA-related BALs, 12 are associated with CVD.

CONCLUSIONS

We identified a PA-related bioactive lipidome profile out of which 12 BALs also had opposite associations with incident CVD events.

An organophotocatalytic late-stage N-CH3 oxidation of trialkylamines to N-formamides with O2 in continuous flow

We report an organophotocatalytic, N-CH3-selective oxidation of trialkylamines in continuous flow. Based on the 9,10-dicyanoanthracene (DCA) core, a new catalyst (DCAS) was designed with solubilizing groups for flow processing. This allowed O2 to be harnessed as a sustainable oxidant for late-stage photocatalytic N-CH3 oxidations of complex natural products and active pharmaceutical ingredients bearing functional groups not tolerated by previous methods. The organophotocatalytic gas-liquid flow process affords cleaner reactions than in batch mode, in short residence times of 13.5 min and productivities of up to 0.65 g per day. Spectroscopic and computational mechanistic studies showed that catalyst derivatization not only enhanced solubility of the new catalyst compared to poorly-soluble DCA, but profoundly diverted the photocatalytic mechanism from singlet electron transfer (SET) reductive quenching with amines toward energy transfer (EnT) with O2.

Opioids: Understanding How Acute Actions Impact Chronic Consequences

In the last decade, critical-care nurses have seen a surge in acute opioid overdose admissions to intensive care units; there have also been significant increases in intensive care unit admissions due to opioid-related illness such as dependence, tolerance, and hyperalgesia. Despite these issues, opioids continue to be the criterion standard of pain management, and the search for opioid alternatives has not produced a clear replacement. A contributor to this problem has been the prevailing opinion that once bound to a receptor, all opioids engaged in the same types of intracellular signaling, which resulted in the same types of responses, only differing in the magnitude of those responses. Contemporary research with G-protein-coupled receptor models (eg, opioids) has demonstrated that this oversimplification is incorrect or incomplete. Understanding the complexity of opioid pharmacodynamics and pharmacokinetics helps us to grasp the intricacies of opioid-related adverse effects. Although there are many potential adverse effects related to opioids, this review focuses on the major adverse effects commonly seen in critical care, namely, respiratory depression, tolerance, hyperalgesia, and central sensitization. In addition, a case study has been incorporated to aid in understanding of strategies nurses can incorporate into their practices: that help mitigate the development of these effects.

A Narrative Review on Perioperative Pain Management Strategies in Enhanced Recovery Pathways-The Past, Present and Future

Effective pain management is a key component in the continuum of perioperative care to ensure optimal outcomes for surgical patients. The overutilization of opioids in the past few decades for postoperative pain control has been a major contributor to the current opioid epidemic. Multimodal analgesia (MMA) and enhanced recovery after surgery (ERAS) pathways have been repeatedly shown to significantly improve postoperative outcomes such as pain, function and satisfaction. The current review aims to examine the history of perioperative MMA strategies in ERAS and provide an update with recent evidence. Furthermore, this review details recent advancements in personalized pain medicine. We speculate that the next important step for improving perioperative pain management could be through incorporating these personalized metrics, such as clinical pharmacogenomic testing and patient-reported outcome measurements, into ERAS program.

Members of the same pharmacological family are not alike: Different opioids, different consequences, hope for the opioid crisis?

Pain management is the specialized medical practice of modulating pain perception and thus easing the suffering and improving the life quality of individuals suffering from painful conditions. Since this requires the modulation of the activity of endogenous systems involved in pain perception, and given the large role that the opioidergic system plays in pain perception, opioids are currently the most effective pain treatment available and are likely to remain relevant for the foreseeable future. This contributes to the rise in opioid use, misuse, and overdose death, which is currently characterized by public health officials in the United States as an epidemic. Historically, the majority of preclinical rodent studies were focused on morphine. This has resulted in our understanding of opioids in general being highly biased by our knowledge of morphine specifically. However, recent in vitro studies suggest that direct extrapolation of research findings from morphine to other opioids is likely to be flawed. Notably, these studies suggest that different opioid analgesics (opioid agonists) engage different downstream signaling effects within the cell, despite binding to and activating the same receptors. This recognition implies that, in contrast to the historical status quo, different opioids cannot be made equivalent by merely dose adjustment. Notably, even at equianalgesic doses, different opioids could result in different beneficial and risk outcomes. In order to foster further translational research regarding drug-specific differences among opioids, here we review basic research elucidating differences among opioids in pharmacokinetics, pharmacodynamics, their capacity for second messenger pathway activation, and their interactions with the immune system and the dopamine D2 receptors.

Acute kidney injury is common with intravenous abuse of extended-release oral oxymorphone and delayed renal recovery rates are associated with increased KDIGO staging

AIM

Prescription opioid abuse poses a serious problem in the United States, representing 615 per 100 000 deaths annually. Extended-release oxymorphone (Opana-ER) is an oral opioid pain medication that has recently been found to cause thrombotic microangiopathy when intravenously abused. In this retrospective study, we attempted to determine the prevalence and outcomes of acute kidney injury (AKI) among patients intravenously abusing extended-release oral oxymorphone.

METHODS

A query of electronic medical records for 'drug abuse' at an academic medical centre during January 2012 to December 2015 was performed and yielded 2350 patients. Patients were further identified by documented intravenous abuse of extended-release oxymorphone. Patients were stratified based on multiple renal indices and outcomes. Potential confounders were also identified.

RESULTS

One hundred and sixty-five patients were found to have a documented history of intravenous abuse of extended-release oral oxymorphone. Prevalence of AKI in this population was a 47.8%. KDIGO stage-I patients consisted of 17.8% of patients with AKI, 40.5% were classified as KDIGO stage-II AKI, and 41.8% were classified as KDIGO stage-III AKI. Among patients with AKI, average age was found to be 37.5 years, 59.4% experienced renal recovery, 56.9% required intensive care unit admission, 13.9% progressed to end-stage renal disease (ESRD), and 7.6% expired during admission.

CONCLUSION

Clinicians should be educated to help recognize intravenous abuse of extended-release oral oxymorphone and its associated effects. Our data suggests AKI is common in these patients; higher KDIGO staging appears to be associated with slower rates of renal recovery, increased comorbidities and progression to both CKD and ESRD.

Pain Therapy Guided by Purpose and Perspective in Light of the Opioid Epidemic

Prescription opioid misuse is an ongoing and escalating epidemic. Although these pharmacological agents are highly effective analgesics prescribed for different types of pain, opioids also induce euphoria, leading to increasing diversion and misuse. Opioid use and related mortalities have developed in spite of initial claims that OxyContin, one of the first opioids prescribed in the USA, was not addictive in the presence of pain. These claims allayed the fears of clinicians and contributed to an increase in the number of prescriptions, quantity of drugs manufactured, and the unforeseen diversion of these drugs for non-medical uses. Understanding the history of opioid drug development, the widespread marketing campaign for opioids, the immense financial incentive behind the treatment of pain, and vulnerable socioeconomic and physical demographics for opioid misuse give perspective on the current epidemic as an American-born problem that has expanded to global significance. In light of the current worldwide opioid epidemic, it is imperative that novel opioids are developed to treat pain without inducing the euphoria that fosters physical dependence and addiction. We describe insights from preclinical findings on the properties of opioid drugs that offer insights into improving abuse-deterrent formulations. One finding is that the ability of some agonists to activate one pathway over another, or agonist bias, can predict whether several novel opioid compounds bear promise in treating pain without causing reward among other off-target effects. In addition, we outline how the pharmacokinetic profile of each opioid contributes to their potential for misuse and discuss the emergence of mixed agonists as a promising pipeline of opioid-based analgesics. These insights from preclinical findings can be used to more effectively identify opioids that treat pain without causing physical dependence and subsequent opioid abuse.

Ketorolac, Oxymorphone, Tapentadol, and Tramadol: A Comprehensive Review

Pain remains a tremendous burden on patients and for the health care system, with uncontrolled pain being the leading cause of disability in this country. There are a variety of medications that can be used in the treatment of pain, including ketorolac, oxymorphone, tapentadol, and tramadol. Depending on the clinical situation, these drugs can be used as monotherapy or in conjunction with other types of medications in a multimodal approach. A strong appreciation of pharmacologic properties of these agents and potential side effects is warranted for clinicians.

Opioid dose and risk of suicide

Chronic pain is associated with increased risk of suicide, and opioids are commonly used to treat moderate to severe pain. However, the association between opioid dose and suicide mortality has not been examined closely. This retrospective data analysis described the risk of suicide associated with differing prescribed opioid doses. Data were from Veterans Affairs health care system treatment records and the National Death Index. Records analyzed were those of Veterans Affairs patients with chronic pain receiving opioids in fiscal years 2004 to 2005 (N = 123,946). Primary predictors were maximum prescribed morphine-equivalent daily opioid dose and opioid fill type. The main outcome measured was suicide death, by any mechanism, and intentional overdose death during 2004 to 2009. Controlling for demographic and clinical characteristics, higher prescribed opioid doses were associated with elevated suicide risk. Compared with those receiving ≤20 milligrams/day (mg/d), hazard ratios were 1.48 (95% confidence intervals [CI], 1.25-1.75) for 20 to <50 mg/d, 1.69 (95% CI, 1.33-2.14) for 50 to <100 mg/d, and 2.15 (95% CI, 1.64-2.81) for 100+ mg/d. The magnitude of association between opioid dose and suicide by intentional overdose was not substantially different from that observed for the overall measure of suicide mortality. Risk of suicide mortality was greater among individuals receiving higher doses of opioids, and treatment providers may want to view high opioid dose as a marker of elevated risk for suicide. Additional research is needed on opioid use, pain treatment, and suicide.

Benzodiazepine prescribing patterns and deaths from drug overdose among US veterans receiving opioid analgesics: case-cohort study

OBJECTIVE

To study the association between benzodiazepine prescribing patterns including dose, type, and dosing schedule and the risk of death from drug overdose among US veterans receiving opioid analgesics.

DESIGN

Case-cohort study.

SETTING

Veterans Health Administration (VHA), 2004-09.

PARTICIPANTS

US veterans, primarily male, who received opioid analgesics in 2004-09. All veterans who died from a drug overdose (n=2400) while receiving opioid analgesics and a random sample of veterans (n=420,386) who received VHA medical services and opioid analgesics.

MAIN OUTCOME MEASURE

Death from drug overdose, defined as any intentional, unintentional, or indeterminate death from poisoning caused by any drug, determined by information on cause of death from the National Death Index.

RESULTS

During the study period 27% (n=112,069) of veterans who received opioid analgesics also received benzodiazepines. About half of the deaths from drug overdose (n=1185) occurred when veterans were concurrently prescribed benzodiazepines and opioids. Risk of death from drug overdose increased with history of benzodiazepine prescription: adjusted hazard ratios were 2.33 (95% confidence interval 2.05 to 2.64) for former prescriptions versus no prescription and 3.86 (3.49 to 4.26) for current prescriptions versus no prescription. Risk of death from drug overdose increased as daily benzodiazepine dose increased. Compared with clonazepam, temazepam was associated with a decreased risk of death from drug overdose (0.63, 0.48 to 0.82). Benzodiazepine dosing schedule was not associated with risk of death from drug overdose.

CONCLUSIONS

Among veterans receiving opioid analgesics, receipt of benzodiazepines was associated with an increased risk of death from drug overdose in a dose-response fashion.

Alternative routes to oral opioid administration in palliative care: a review and clinical summary

OBJECTIVE

A major goal of palliative care is to provide comfort, and pain is one of the most common causes of treatable suffering in patients with advanced disease. Opioids are indispensable for pain management in palliative care and can usually be provided by the oral route, which is safe, effective, and of lowest cost in most cases. As patients near the end of life, however, the need for alternate routes of medication increases with up to 70% of patients requiring a nonoral route for opioid administration. In order to optimize patient care, it is imperative that clinicians understand existing available options of opioid administration and their respective advantages and disadvantages.

METHODS

We performed a literature review to describe the most commonly used and available routes that can substitute for oral opioid therapy and to provide a summary of factors affecting choice of opioid for use in palliative care in terms of benefits, indications, cautions, and general considerations.

RESULTS

Clinical circumstances will largely dictate appropriateness of the route selected. When the oral route is unavailable, subcutaneous, intravenous, and enteral routes are preferred in the palliative care population. The evidence supporting sublingual, buccal, rectal, and transdermal gel routes is mixed.

CONCLUSIONS

This review is not designed to be a critical appraisal of the quality of current evidence; rather, it is a summation of that evidence and of current clinical practices regarding alternate routes of opioid administration. In doing so, the overarching goal of this review is to support more informed clinical decision making.

Sulfation of opioid drugs by human cytosolic sulfotransferases: metabolic labeling study and enzymatic analysis

The current study was designed to examine the sulfation of eight opioid drugs, morphine, hydromorphone, oxymorphone, butorphanol, nalbuphine, levorphanol, nalorphine, and naltrexone, in HepG2 human hepatoma cells and human organ samples (lung, liver, kidney, and small intestine) and to identify the human SULT(s) responsible for their sulfation. Analysis of the spent media of HepG2 cells, metabolically labeled with [35S]sulfate in the presence of each of the eight opioid drugs, showed the generation and release of corresponding [35S]sulfated derivatives. Five of the eight opioid drugs, hydromorphone, oxymorphone, butorphanol, nalorphine, and naltrexone, appeared to be more strongly sulfated in HepG2 cells than were the other three, morphine, nalbuphine, and levorphanol. Differential sulfating activities toward the opioid drugs were detected in cytosol or S9 fractions of human lung, liver, small intestine, and kidney, with the highest activities being found for the liver sample. A systematic analysis using eleven known human SULTs and kinetic experiment revealed SULT1A1 as the major responsible SULTs for the sulfation of oxymorphone, nalbuphine, nalorphine, and naltrexone, SULT1A3 for the sulfation of morphine and hydromorphone, and SULT2A1 for the sulfation of butorphanol and levorphanol. Collectively, the results obtained imply that sulfation may play a significant role in the metabolism of the tested opioid drugs in vivo.

Validation of blood and liver oxymorphone analysis using LC-MS-MS: concentrations in 30 fatal overdoses

A sensitive liquid chromatography-tandem mass spectrometry method was developed and validated for the quantitation of oxymorphone (OM) in human whole blood and liver. Sample preparation was done by solid-phase extraction, using deuterated OM as the internal standard. Separation was achieved using a Waters Aquity UPLC HSS T3 column. Analysis utilized positive electrospray ionization and multiple reaction monitoring. As part of the validation, studies were conducted to determine potential interference, selectivity, ion suppression/enhancement and carryover. Calibration model, limit of detection (LOD), lower limit of quantitation (LLOQ), precision and accuracy were also established. The linear range of the method was 2-500 ng/mL in blood and 5-500 ng/g in the liver. The LOD and LLOQ were 2 ng/mL for blood and 5 ng/g for the liver. Blood and/or liver specimens from 30 cases were analyzed. OM concentrations ranged from 23 to 554 ng/mL ( , n = 26) in blood and 48 to 1740 ng/g ( , n = 30) in the liver.

Pharmacokinetics of ammonium sulfate gradient loaded liposome-encapsulated oxymorphone and hydromorphone in healthy dogs

OBJECTIVE

To evaluate the pharmacokinetics, in dogs, of liposome-encapsulated oxymorphone and hydromorphone made by the ammonium sulfate gradient loading technique (ASG).

ANIMALS

Four healthy purpose-bred Beagles aged 9.5 ± 3.2 months and weighing 13.4 ± 2.3 kg.

STUDY DESIGN

Randomized cross-over design.

METHODS

Each dog was given either 4.0 mg kg(-1) of ASG-oxymorphone or 8.0 mg kg(-1) of ASG-hydromorphone SC on separate occasions with a 3-month washout period. Blood was collected at baseline and at serial time points up to 1032 hours (43 days) after injection for determination of serum opioid concentrations. Serum opioid concentrations were measured with HPLC-MS and pharmacokinetic parameters were calculated using commercial software and non-compartmental methods.

RESULTS

Serum concentrations of oxymorphone remained above the limit of quantification for 21 days, while those for hydromorphone remained above the limit of quantification for 29 days. Cmax for ASG-oxymorphone was 7.5 ng mL(-1) ; Cmax for ASG-hydromorphone was 5.7 ng mL(-1) .

CONCLUSIONS AND CLINICAL RELEVANCE

Oxymorphone and hydromorphone, when encapsulated into liposomes using the ammonium sulfate gradient loading technique, result in measureable serum concentrations for between 3 to 4 weeks. This formulation may have promise in the convenient use of opioids for clinical treatment of chronically painful conditions in dogs.

Opioids for chronic pain: new evidence, new strategies, safe prescribing

In the United States, the prevalence and burden of chronic pain is large and still growing. Older adults (aged ≥65 years) make up a large portion of the population with chronic pain, and their presentation, diagnosis, and treatment tends to be more complicated because of age-related physiological changes and comorbidities. Guidelines on treating patients with severe back pain recommend opioids as an option for those who do not find adequate pain relief from acetaminophen or nonsteroidal anti-inflammatory drugs (NSAIDs). For older adult patients at higher risk for NSAID-related adverse effects, such as those who have gastrointestinal or cardiovascular disease, diabetes mellitus, or who are taking low-dose aspirin, opioids are recommended instead. Opioids may also be an appropriate option for patients with neuropathic pain who have not achieved adequate analgesia from maximum doses of first- and second-line antineuropathic agents. Still, opioids are not appropriate for all patients; rather, a differential diagnosis, consideration of other comorbidities, and the potential for opioid-related adverse effects and substance abuse are required to confirm the value of opioid treatment for each individual. For nonresponders to opioid therapy, opioid rotation should be considered before discontinuation is pursued.

Pharmacokinetic and pharmacodynamic modeling of opioid-induced gastrointestinal side effects in patients receiving tapentadol IR and oxycodone IR

PURPOSE

To understand the relationship between the risk of opioid-related gastrointestinal adverse effects (AEs) and exposure to tapentadol and oxycodone as well as its active metabolite, oxymorphone, using pharmacokinetic/pharmacodynamic models.

METHODS

The analysis was based on a study in patients with moderate-to-severe pain following bunionectomy. Population PK modeling was conducted to estimate population PK parameters for tapentadol, oxycodone, and oxymorphone. Time to AEs was analyzed using Cox proportional-hazards models.

RESULTS

Risk of nausea, vomiting, and constipation significantly increased with exposure to tapentadol or oxycodone/oxymorphone. However, elevated risk per drug exposure of AEs for tapentadol was ~3-4 times lower than that of oxycodone, while elevated AE risk per drug exposure of oxycodone was ~60 times lower than that for oxymorphone, consistent with reported in vitro receptor binding affinities for these compounds. Simulations show that AE incidence following administration of tapentadol IR is lower than that following oxycodone IR intake within the investigated range of analgesic noninferiority dose ratios.

CONCLUSIONS

This PK/PD analysis supports the clinical findings of reduced nausea, vomiting and constipation reported by patients treated with tapentadol, compared to patients treated with oxycodone.

The metabolism of opioid agents and the clinical impact of their active metabolites

BACKGROUND

The metabolism of opioids is critical to consider for multiple reasons. The most commonly prescribed opioid agents often have metabolites that are active and are the source of both analgesic activity and an increased incidence of adverse events. Many opioids are metabolized by cytochrome P450 enzymes. Polymorphisms in cytochrome P450 genes and inhibition or induction of cytochrome P450 enzymes by coadministered drugs may significantly impact the systemic concentration of opioids and their metabolites and the associated efficacy or adverse events.

METHODS

This is a narrative review of the metabolism of various opioids that will highlight the impact of their active metabolites, and the potential impact of cytochrome P450 activity on analgesic activity.

RESULTS

An understanding of "opioid metabolic machinery," cytochrome P450 activity, and drug-drug interactions in the context of opioid selection may benefit clinicians and patients alike.

CONCLUSIONS

A greater appreciation of the metabolism of commonly prescribed opioid analgesics and the impact of their active metabolites on efficacy and safety may aid prescribers in tailoring care for optimal outcomes.

The management of cancer pain

The experience of pain in cancer is widely accepted as a major threat to quality of life, and the relief of pain has emerged as a priority in oncology care. Pain is associated with both the disease as well as treatment, and management is essential from the onset of early disease through long-term survivorship or end-of-life care. Effective relief of pain is contingent upon a comprehensive assessment to identify physical, psychological, social, and spiritual aspects and as a foundation for multidisciplinary interventions. Fortunately, advances in pain treatment and in the field of palliative care have provided effective treatments encompassing pharmacological, cognitive-behavioral, and other approaches. The field of palliative care has emphasized that attention to symptoms such as pain is integral to quality cancer care.

Exposure to oral oxycodone is increased by concomitant inhibition of CYP2D6 and 3A4 pathways, but not by inhibition of CYP2D6 alone

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Oxycodone is an opioid analgesic that is metabolized mainly in the liver by cytochrome P450 (CYP) 2D6 and 3A4 enzymes. So far, the effects of CYP2D6 or CYP3A4 inhibitors on the pharmacokinetics of oxycodone in humans have not been systematically studied.

WHAT THIS STUDY ADDS

Drug interactions arising from CYP2D6 inhibition most likely have minor clinical importance for oral oxycodone. When both of CYP2D6 and CYP3A4 pathways are inhibited, the exposure to oral oxycodone is increased substantially.

AIM

The aim of this study was to find out whether the inhibition of cytochrome P450 2D6 (CYP2D6) with paroxetine or concomitant inhibition of CYP2D6 and CYP3A4 with paroxetine and itraconazole, altered the pharmacokinetics and pharmacological response of orally administered oxycodone.

METHODS

A randomized placebo-controlled cross-over study design with three phases was used. Eleven healthy subjects ingested 10 mg of oral immediate release oxycodone on the fourth day of pre-treatment with either placebo, paroxetine (20 mg once daily) or paroxetine (20 mg once daily) and itraconazole (200 mg once daily) for 5 days. The plasma concentrations of oxycodone and its oxidative metabolites were measured for 48 h, and pharmacological (analgesic and behavioural) effects were evaluated.

RESULTS

Paroxetine alone reduced the area under concentration-time curve (AUC(0,0-48 h)) of the CYP2D6 dependent metabolite oxymorphone by 44% (P < 0.05), but had no significant effects on the plasma concentrations of oxycodone or its pharmacological effects when compared with the placebo phase. When both oxidative pathways of the metabolism of oxycodone were inhibited with paroxetine and itraconazole, the mean AUC(0,infinity) of oxycodone increased by 2.9-fold (P < 0.001), and its C(max) by 1.8-fold (P < 0.001). Visual analogue scores for subjective drug effects, drowsiness and deterioration of performance were slightly increased (P < 0.05) after paroxetine + itraconazole pre-treatment when compared with placebo.

CONCLUSIONS

Drug interactions arising from CYP2D6 inhibition most likely have minor clinical importance for oral oxycodone if the function of the CYP3A4 pathway is normal. When both CYP2D6 and CYP3A4 pathways are inhibited, the exposure to oral oxycodone is increased substantially.

A systematic review of oxymorphone in the management of chronic pain

Opioids are recommended for control of moderate-to-severe, chronic, malignant, and nonmalignant pain. A controlled-release formulation of the opioid oxymorphone has recently been launched. The aim of this review was to assess the effectiveness of oxymorphone as an analgesic in chronic pain. A systematic search for published studies of oral oxymorphone in the management of chronic pain was conducted. The studies were evaluated for their internal validity according to standard criteria. They were also evaluated for their external validity and research ethic aspects. A meta-analysis was performed to examine the effect of oxymorphone compared with placebo. Nine studies were evaluated; three were excluded because of low quality. Six controlled studies (duration 2-12 weeks) included a total of 1489 subjects suffering from chronic low back pain, chronic pain from osteoarthritis, and chronic cancer pain. Three of the studies were of high quality and three of medium quality. External validity was assessed to be high, medium, and low (in one, three, and two studies, respectively). The meta-analysis suggests that daily doses of 40-100mg are superior to placebo; however, the estimate (reduction of pain intensity compared with placebo) of the treatment effect is imprecise (95% confidence interval -17.08, -8.69). Limited evidence suggests that oxymorphone is effective for pain control in patients with cancer. No significant differences between oxymorphone and oxycodone at equipotent doses were found. In conclusion, oxymorphone is superior to placebo. There is no evidence that the efficacy of oxymorphone differs from other opioids.

St John's wort greatly reduces the concentrations of oral oxycodone

BACKGROUND

Chronic pain is associated with depression. Self-treatment of depression with herbal over-the-counter medicine St John's wort makes pain patients prone to drug interactions.

AIMS

The aim of this study was to assess the potential of St John's wort to alter the CYP3A-mediated metabolism of a mu-opioid receptor agonist, oxycodone.

METHODS

The study design was placebo-controlled, randomized, cross-over with two phases at intervals of 4 weeks and was conducted with 12 healthy participants. St John's wort (Jarsin) or placebo was administered t.i.d. for 15 days and oral oxycodone hydrochloride 15 mg on day 14. Oxycodone pharmacokinetics and pharmacodynamics were compared after St John's wort or placebo. Behavioural and analgesic effects were assessed with subjective visual analogue scales and cold pressor test. Plasma drug concentrations were measured from 0 to 48 h, behavioural and analgesic effects from 0 to 12 h.

RESULTS

Following St John's wort administration the oxycodone AUC decreased 50% (p<0.001). Oxycodone elimination half-life shortened from a mean+/-SD 3.8+/-0.7 to 3.0+/-0.4h (p<0.001). The self-reported drug effect of oxycodone as measured by AUEC(0-12) decreased significantly (p=0.004). Differences between St John's wort and placebo phases in cold pain threshold and intensity AUEC(0-12) were not observed.

CONCLUSIONS

St John's wort greatly reduced the plasma concentrations of oral oxycodone. The self-reported drug effect of oxycodone decreased significantly. This interaction may potentially be of some clinical significance when treating patients with chronic pain.

Opioid switching and rotation in primary care: implementation and clinical utility

BACKGROUND

Opioid therapy is the standard treatment for moderate-to-severe cancer pain and is becoming a more frequent treatment for moderate-to-severe chronic noncancer pain. Response to opioids varies significantly between patients and even within the individual patient at different stages of treatment. Finding an opioid at a dose that provides adequate long-term analgesia with minimal adverse effects can be difficult. Opioid switching and opioid rotation, at different stages of therapy, represent two clinical strategies used to optimize opioid response for patients with moderate-to-severe pain.

OBJECTIVES

Review the theoretical and clinical evidence supporting the concepts of opioid switching and rotation, outline the conditions under which these practices should be considered, and briefly suggest practical steps for their implementation.

SCOPE

Clinical literature, clinical practice and guideline databases, and professional society websites were searched for articles or reports describing opioid switching or opioid rotation in chronic pain therapy; variability in patient response to opioid therapy; physiologic, pharmacologic, and genetic factors that affect clinical response to opioids; and practical approaches to maximizing analgesia and minimizing adverse effects in opioid therapy. It is outside the scope of this review to evaluate the pharmacoeconomic aspects that affect changes in opioid therapy.

FINDINGS

The variability in de novo clinical response to opioids likely represents the interaction of the varying properties of the individual opioids with the variability in individual patient biology. This interaction forms the rationale for opioid switching and explains its clinical utility. As with opioid switching, success with opioid rotation is related to the myriad of factors determining an individual patient's response to a specific opioid. However, the benefits of opioid rotation also derive from a partial reversal of tolerance at the mu-opioid receptor and the response of different micro-opioid receptor subtypes to the different opioids.

Role of active metabolites in the use of opioids

The opioid class of drugs, a large group, is mainly used for the treatment of acute and chronic persistent pain. All are eliminated from the body via metabolism involving principally CYP3A4 and the highly polymorphic CYP2D6, which markedly affects the drug's function, and by conjugation reactions mainly by UGT2B7. In many cases, the resultant metabolites have the same pharmacological activity as the parent opioid; however in many cases, plasma metabolite concentrations are too low to make a meaningful contribution to the overall clinical effects of the parent drug. These metabolites are invariably more water soluble and require renal clearance as an important overall elimination pathway. Such metabolites have the potential to accumulate in the elderly and in those with declining renal function with resultant accumulation to a much greater extent than the parent opioid. The best known example is the accumulation of morphine-6-glucuronide from morphine. Some opioids have active metabolites but at different target sites. These are norpethidine, a neurotoxic agent, and nordextropropoxyphene, a cardiotoxic agent. Clinicians need to be aware that many opioids have active metabolites that will become therapeutically important, for example in cases of altered pathology, drug interactions and genetic polymorphisms of drug-metabolizing enzymes. Thus, dose individualisation and the avoidance of adverse effects of opioids due to the accumulation of active metabolites or lack of formation of active metabolites are important considerations when opioids are used.

Cancer pain and analgesia

Pain ranges in prevalence from 14-100% among cancer patients and occurs in 50-70% of those in active treatment. Cancer pain may result from direct invasion of tumor into nerves, bones, soft tissue, ligaments, and fascia, and may induce visceral pain through distension and obstruction. Cancer pain is multifaceted. Clinicians may describe cancer pain as acute, chronic, nociceptive (somatic), visceral, or neuropathic. Despite implementation of the WHO guidelines, reports of undertreatment of cancer pain persist in various clinical settings and in spite of decades of work to reduce unnecessary discomfort. Substantial obstacles to adequate pain relief with opioids include specific concerns of patients themselves, their family members, physicians, nurses, and the healthcare system. The WHO analgesic ladder serves as the mainstay of treatment for the relief of cancer pain in concert with tumoricidal, surgical, interventional, radiotherapeutic, psychological, and rehabilitative modalities. This multidimensional approach offers the greatest potential for maximizing analgesia and minimizing adverse effects. Primary therapies are directed at the source of the cancer pain and may enhance a patient's function, longevity, and comfort. Adjuvant therapies include nonopioids that confer analgesic effects in certain medical conditions but primarily treat conditions that do not involve pain. Nonopioid medications (over-the-counter agents) are useful in the management of mild to moderate pain, and their continuation through step 3 of the WHO ladder is an option after weighing a drug's risks and benefits in individual patients. Symptomatic treatment of severe cancer pain should begin with an opioid, regardless of the mechanism of the pain. They are very effective analgesics, titrate easily, and offer a favorable risk/benefit ratio. Cancer pain remains inadequately controlled despite the diagnostic and therapeutic means of ensuring that patients feel comfortable during their illness. Therefore, all practitioners need to make control of cancer pain a professional duty, even if they can only use the most basic and least expensive analgesic medications, such as morphine, codeine, and acetaminophen, to reduce human suffering.

Advanced formulation design: improving drug therapies for the management of severe and chronic pain

Chronic pain is a condition affecting a vast patient population and resulting in billions of dollars in associated health care costs annually. Sufferers from severe chronic pain often require [correction of requite] twenty-four hour drug treatment through intrusive means and/or repeated oral dosing. Although the oral route of administration is most preferred, conventional immediate release oral dosage forms lead to inconvenient and suboptimal drug therapies for the treatment of chronic pain. Effective drug therapies for the management of chronic pain therefore require advanced formulation design to optimize the delivery of potent analgesic agents. Ideally, these advanced delivery systems provide efficacious pain therapy with minimal side effects via a simple and convenient dosing regime. In this article, currently commercialized and developing drug products for pain management are reviewed with respect to dosage form design as well as clinical efficacy. The drug delivery systems reviewed herein represent advanced formulation designs that are substantially improving analgesic drug therapies.

Oral extended-release oxymorphone: a new choice for chronic pain relief

Opana ER (oxymorphone extended release [ER]) is a new oral long-acting formulation indicated for the treatment of moderate to severe chronic pain. Because the ER matrix slowly releases oxymorphone over 12 h, consistent plasma levels are produced with low peak-to-trough fluctuations. Oxymorphone ER is the only long-acting opioid that contains oxymorphone, which exhibits some distinct pharmacologic properties compared with most other opioids, including a longer half-life, higher affinity for the micro-opioid receptor, and lack of interaction with the CYPP450 drug-metabolizing system. With a safety and tolerability profile similar to other opioids and documented efficacy in several models of chronic pain (low back, cancer, and osteoarthritis), oxymorphone ER provides a new option for clinicians and patients in the treatment of chronic pain.

Fentanyl buccal tablet (FBT) for relief of breakthrough pain in opioid-treated patients with chronic low back pain: a randomized, placebo-controlled study

BACKGROUND

Short-acting opioids are commonly used to treat breakthrough pain (BTP) and rapid-onset formulations are being developed to improve the effectiveness of this approach. Fentanyl buccal tablet (FBT) is a new formulation of fentanyl that enhances transbuccal drug delivery via an effervescent reaction and may provide relatively rapid-onset analgesia. FBT was evaluated for BTP in opioid-treated patients with chronic low back pain--the first such study in a population with chronic non-cancer pain.

DESIGN

Randomized, double-blind, placebo-controlled.

PATIENTS AND SETTING

Patients with chronic low back pain receiving long-term opioid therapy at 16 pain treatment centers in the United States.

PROCEDURES

Following open-label titration to identify an effective FBT dose, patients were randomly assigned to one of three double-blind dose sequences (six doses of FBT, three placebo) to treat nine BTP episodes. Pain intensity (PI), measured on an 11-point scale (0 = no pain; 10 = worst pain), and other outcomes were assessed for 2 h after dosing.

DATA ANALYSIS

The primary efficacy measure was the sum of pain intensity differences (PIDs) for the first 60 min (SPID60); secondary efficacy measures included PIDs at other time points, pain relief (PR), meaningful PR, time to meaningful PR, use of supplementary BTP medication, and self/investigator-reported adverse events.

RESULTS

Of the 124 patients screened, 105 patients were enrolled, 84 identified an effective FBT dose, and 77 entered the double-blind phase. SPID60 significantly favored FBT (p < 0.0001). All secondary measures also favored FBT, with PIDs and PR showing significant differences versus placebo as early as 10 and 15 min, respectively. An improvement in PI score of > or = 33% occurred in a significantly larger proportion of FBT-treated episodes versus placebo from 15 min (20% vs. 11%, p < 0.01) through 2 h (65% vs. 28%, p < 0.0001). Patients were approximately four times more likely to require supplemental opioids for BTP episodes following administration of placebo compared with episodes treated with FBT. AEs were typical for opioids, and were mostly reported during dose titration. Limitations of this study may be related to its open-label dose-titration phase (which has the potential to compromise blinding) and the recruitment of patients from pain clinics, which could potentially yield a study population that is not representative of the general population with BTP.

CONCLUSIONS

FBT was efficacious and well tolerated in the treatment of BTP in opioid-treated patients with chronic low back pain.