Single- and Multiple-Dose Pharmacokinetic and Dose-Proportionality Study of??Oxymorphone Immediate-Release Tablets

Hydrocodone, Oxycodone, and Morphine Metabolism and Drug-Drug Interactions

Awareness of drug interactions involving opioids is critical for patient treatment as they are common therapeutics used in numerous care settings, including both chronic and disease-related pain. Not only do opioids have narrow therapeutic indexes and are extensively used, but they have the potential to cause severe toxicity. Opioids are the classical pain treatment for patients who suffer from moderate to severe pain. More importantly, opioids are often prescribed in combination with multiple other drugs, especially in patient populations who typically are prescribed a large drug regimen. This review focuses on the current knowledge of common opioid drug-drug interactions (DDIs), focusing specifically on hydrocodone, oxycodone, and morphine DDIs. The DDIs covered in this review include pharmacokinetic DDI arising from enzyme inhibition or induction, primarily due to inhibition of cytochrome p450 enzymes (CYPs). However, opioids such as morphine are metabolized by uridine-5'-diphosphoglucuronosyltransferases (UGTs), principally UGT2B7, and glucuronidation is another important pathway for opioid-drug interactions. This review also covers several pharmacodynamic DDI studies as well as the basics of CYP and UGT metabolism, including detailed opioid metabolism and the potential involvement of metabolizing enzyme gene variation in DDI. Based upon the current literature, further studies are needed to fully investigate and describe the DDI potential with opioids in pain and related disease settings to improve clinical outcomes for patients. SIGNIFICANCE STATEMENT: A review of the literature focusing on drug-drug interactions involving opioids is important because they can be toxic and potentially lethal, occurring through pharmacodynamic interactions as well as pharmacokinetic interactions occurring through inhibition or induction of drug metabolism.

Contribution of CYP2D6 Functional Activity to Oxycodone Efficacy in Pain Management: Genetic Polymorphisms, Phenoconversion, and Tissue-Selective Metabolism

Oxycodone is a widely used opioid for the management of chronic pain. Analgesic effects observed following the administration of oxycodone are mediated mostly by agonistic effects on the μ-opioid receptor. Wide inter-subject variability observed in oxycodone efficacy could be explained by polymorphisms in the gene coding for the μ-opioid receptor (OPRM1). In humans, oxycodone is converted into several metabolites, particularly into oxymorphone, an active metabolite with potent μ-opioid receptor agonist activity. The CYP2D6 enzyme is principally responsible for the conversion of oxycodone to oxymorphone. The CYP2D6 gene is highly polymorphic with encoded protein activities, ranging from non-functioning to high-functioning enzymes. Several pharmacogenetic studies have shown the importance of CYP2D6-mediated conversion of oxycodone to oxymorphone for analgesic efficacy. Pharmacogenetic testing could optimize oxycodone therapy and help achieve adequate pain control, avoiding harmful side effects. However, the most recent Clinical Pharmacogenetics Implementation Consortium guidelines fell short of recommending pharmacogenomic testing for oxycodone treatment. In this review, we (1) analyze pharmacogenomic and drug-interaction studies to delineate the association between CYP2D6 activity and oxycodone efficacy, (2) review evidence from CYP3A4 drug-interaction studies to untangle the nature of oxycodone metabolism and its efficacy, (3) report on the current knowledge linking the efficacy of oxycodone to OPRM1 variants, and (4) discuss the potential role of CYP2D6 brain expression on the local formation of oxymorphone. In conclusion, we opine that pharmacogenetic testing, especially for CYP2D6 with considerations of phenoconversion due to concomitant drug administration, should be appraised to improve oxycodone efficacy.

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.

Prescription Opioids. V. Metabolism and Excretion of Oxymorphone in Urine Following Controlled Single Dose Administration

Oxymorphone (OM), a prescription opioid and metabolite of oxycodone, was included in the recently published proposed revisions to the Mandatory Guidelines for Federal Workplace Drug Testing Programs. To facilitate toxicological interpretation, this study characterized the time course of OM and its metabolite, noroxymorphone (NOM), in hydrolyzed and non-hydrolyzed urine specimens. Twelve healthy subjects were administered a single 10 mg controlled-release OM dose, followed by a periodic collection of pooled urine specimens for 54 h following administration. Analysis for free and total OM and NOM was conducted by liquid chromatography tandem mass spectrometry (LC-MS-MS), at a 50 ng/mL limit of quantitation (LOQ). Following enzymatic hydrolysis, OM and NOM were detected in 89.9% and 13.5% specimens, respectively. Without hydrolysis, OM was detected in 8.1% specimens, and NOM was not detected. The mean ratio of hydrolyzed OM to NOM was 41.6. OM was frequently detected in the first pooled collection 0-2 h post-dose, appearing at a mean of 2.4 h. NOM appeared at a mean of 8.3 h. The period of detection at the 50 ng/mL threshold averaged 50.7 h for OM and 11.0 h for NOM. These data support that OM analysis conducted using a 50 ng/mL threshold should include hydrolysis or optimize sensitivity for conjugated OM.

Pharmacodynamic effects of oral oxymorphone: abuse liability, analgesic profile and direct physiologic effects in humans

Oxymorphone is a semisynthetic μ-opioid agonist, marketed as a prescription analgesic purported to be twice as potent as oxycodone for pain relief. Oral formulations of oxymorphone were reintroduced in the United States in 2006 and reports of abuse ensued; however, there are limited data available on its pharmacodynamic effects. The current study aimed to examine the direct physiologic effects, relative abuse liability, analgesic profile and overall pharmacodynamic potency of oxymorphone in comparison with identical doses of oxycodone. Healthy, non-dependent opioid abusers (n = 9) were enrolled in this within-subject, double-blind, placebo-controlled, 3-week inpatient study. Seven experimental sessions (6.5 hours) were conducted, during which an oral dose of immediate-release formulations of oxymorphone (10, 20 and 40 mg), oxycodone (10, 20 and 40 mg) or placebo was administered. An array of physiologic, abuse liability and experimental pain measures was collected. At identical doses, oxymorphone produced approximately twofold less potent effects on miosis, compared with oxycodone. Oxymorphone also produced lesser magnitude effects on measures of respiratory depression, two experimental pain models and observer-rated agonist effects. However, 40 mg of oxymorphone was similar to 40 mg of oxycodone on several abuse-related subjective ratings. Formal relative potency analyses were largely invalid because of the substantially greater effects of oxycodone. Overall, oxymorphone is less potent on most pharmacodynamic measures, although at higher doses, its abuse liability is similar to oxycodone. These data suggest that the published clinical equianalgesic estimates may not be consistent with the observed direct physiologic effects of opioids, results of experimental pain models or abuse liability measures, as assessed in the human laboratory.

Practical approaches to pharmacologic management of pain in older adults with cancer

PURPOSE/OBJECTIVES

To identify appropriate strategies for pharmacotherapeutic agents in the management of pain in older adults with cancer.

DATA SOURCES

PubMed literature searches, personal reference collection, and clinical experience.

DATA SYNTHESIS

To make good decisions about pain management when developing treatment plans for older adults, healthcare providers should focus on the pharmacokinetic and pharmacodynamic properties of drugs in the context of the physiologic changes that occur with aging.

CONCLUSIONS

Unrelieved pain can have a detrimental effect on older adults; conversely, overmedicating can lead to an increased risk of adverse events. With advancing age, physiologic changes alter the pharmacokinetic and pharmacodynamic properties of drugs by reducing their absorption, changing their distribution, and modifying their metabolism and elimination. Also, common comorbidities increase the risk of pharmacologic toxicity and narrow the therapeutic window. In addition, polypharmacy-an issue more common in older adults-increases the complexity of prescribing and risk of adverse events. Consequently, older adults require individualization of their pharmacotherapies. Healthcare providers should consider carefully the risks and benefits of nonsteroidal anti-inflammatory drugs, opioids, and adjuvants before initiating an analgesic trial. The 2009 guidelines published by the American Geriatrics Society described several key principles for prescribing analgesics to older adults and offered specific recommendations and caveats for each drug class.

IMPLICATIONS FOR NURSING

Current guidelines support appropriate management of cancer pain in older adults with specific recommendations for each class of analgesics as well as general prescribing principles.

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.

Pharmacological management of neuropathic pain in older adults: an update on peripherally and centrally acting agents

The burden of neuropathic pain in older adults is great and the practitioner is challenged to reduce symptoms and improve quality of life. Many common neuropathic pain syndromes are more prevalent in the older population, and older adults also carry greater sensitivity to certain side effects. The health care professional should have a thorough familiarity with all medications available to treat this difficult group of disorders.

Exploratory assessment of dose proportionality: review of current approaches and proposal for a practical criterion

This article reviews currently used approaches for establishing dose proportionality in Phase I dose escalation studies. A review of relevant literature between 2002 and 2006 found that the power model was the preferred choice for assessing dose proportionality in about one-third of the articles. This article promotes the use of the power model and a conceptually appealing extension, i.e. a criterion based on comparing the 90% confidence interval for the ratio of predicted mean values from the extremes of the dose range (R(dnm)) to pre-defined equivalence criterion (theta(L),theta(U)). The choice of bioequivalence default values of theta(L)=0.8 and theta(U)=1.25 seems reasonable for dose levels only a doubling apart but are impractically strict when applied over the complete dose range. Power calculations are used to show that this prescribed criterion lacks power to conclude dose proportionality in typical Phase I dose-escalation studies. A more lenient criterion with values theta(L)=0.5 and theta(U)=2 is proposed for exploratory dose proportionality assessments across the complete dose range.

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.

Current developments in opioid therapy for management of cancer pain

Pain remains a highly prevalent problem for patients with cancer and typically falls into one of 3 types: visceral, somatic, and neuropathic. A mechanistic, pathophysiologic approach to pain management involves a good assessment of the type of pain, followed by tailoring of the treatment based on the diagnosis. This pain management strategy can provide rapid pain control with a lower incidence of complications and side effects than other methods. Furthermore, pharmacogenetics may play an important role in individualizing therapies in the future, but for now this type of data offers explanations for phenomena commonly observed in clinical practice, such as (1) differences in individual analgesic and side-effect responses to various opioid agents, (2) incomplete cross-tolerance seen when switching between mu opioid analgesics, and (3) why opioid rotation can be beneficial for patients after an opioid therapy loses efficacy or becomes associated with intolerable side effects. Especially for difficult-to-manage pain patients, additions to the opioid analgesic armamentarium can potentially better individualize pain management, and provide another option to be used for opioid rotation. Among the most recent Food and Drug Administration-approved opioid analgesics for acute pain and persistent pain are oral immediate-release and extended-release formulations of oxymorphone, whereas for breakthrough pain, the ultrarapid-acting opioid, fentanyl effervescent buccal tablets, has newly been developed and indicated within the United States.

Review of oral oxymorphone in the management of pain

Chronic cancer and nonmalignant pain (CNMP) is a common and major health problem afflicting approximately 40 million persons in the US. Most cancer patients, and many patients with CNMP, require opioid analgesics to obtain adequate pain relief. Oral oxymorphone is a new formulation of an existing parenteral opioid that has become available for the treatment of significant pain: acute postoperative, chronic arthritis, chronic low back, and chronic cancer pain. Oxymorphone is a typical mu-opioid agonist that is effective in both immediate- and extended-release (IR and ER) formulations. Oxymorphone is more lipid soluble than morphine, resulting in a rapid onset of action when given in tablet formulation, with a duration of action of approximately 4-6 hours in IR and 12 hours in ER preparations. Oxymorphone provides excellent pain relief for significant pain, with typical opioid side effects that are usually mild or moderate in intensity. Multiple double-blind, prospective, placebo-controlled clinical trials have demonstrated the clinical efficacy and safety of this new oral opioid preparation. Oral oxymorphone is an effective opioid that provides a new therapeutic option for the physician.

Opioids for persistent noncancer pain

This article concentrates on recent evidence about opioid analgesics for persistent noncancer pain. Evidence confirms that opioids are drugs with a definite risk of adverse events. Therefore, before prescribing opioids, careful consideration must be given to be certain that the intended benefit of a particular opioid merits its use despite the potential side effects and to determine if the co-prescription of other pharmacologic agents could reduce the risk of adverse events. Strong opioids should be reserved for patients who fail to respond to other lower-risk options and only after proper consideration is given to the long-term consequences of strong opioid use. Problems associated with opioids dictate that more efficacious and safer drugs need to be found.

Efficacy and tolerability of oxymorphone immediate release for acute postoperative pain after abdominal surgery: a randomized, double-blind, active- and placebo-controlled, parallel-group trial

BACKGROUND

Patients are typically switched from parenteral opioids to oral opioids during the 24 to 48 hours after surgery. In June 2006, an oral immediate-release (IR) tablet formulation of oxymorphone was approved for the treatment of acute moderate to severe pain. Single doses of oxymorphone IR have been reported to provide significant pain relief after orthopedic surgery.

OBJECTIVE

This study assessed the efficacy and tolerability of multiple fixed doses of oxymorphone IR in the treatment of acute postoperative pain after abdominal surgery.

METHODS

This was a multicenter, randomized, double-blind, active- and placebo-controlled, parallel-group study in men and women aged >or=18 years undergoing abdominal surgery that required a >or=3-cm incision. Patients who discontinued short-acting parenteral opioids and developed moderate or severe pain (4-point categorical scale [none, mild, moderate, or severe] and pain intensity >or=50 mm on a 100-mm visual analog scale [from 0 = no pain to 100 = worst pain imaginable]) within 30 hours after abdominal surgery were randomized to receive oxymorphone IR 10 or 20 mg, oxycodone IR 15 mg, or placebo every 4 to 6 hours after the previous dose. The study included 2 efficacy assessments: a single-dose evaluation for up to 6 hours after the dose, and a multipledose evaluation for up to 48 hours after the first dose. Pain was assessed at 15-minute intervals during the hour after the first dose, hourly thereafter for the next 5 hours, and before each subsequent dose. The primary efficacy end point was the median time to study discontinuation for all causes. Assessment of tolerability was based on the proportion of study discontinuations due to treatment-emergent adverse events (AEs).

RESULTS

Three hundred thirty-one patients were included in the study. Demographic characteristics were similar across all groups: 98.8% (327) of patients were women, and 80.1% (265) of the abdominal surgeries were hysterectomies. The mean (SD) age of the study population was 42.6 (9.3) years. The median time to study discontinuation for all causes was significantly longer for all active treatments compared with placebo (oxymorphone IR 10 mg, 17.9 hours; oxymorphone IR 20 mg, 20.3 hours; oxycodone IR 15 mg, 24.1 hours; placebo, 4.8 hours; P < 0.006). Oxymorphone IR 20 mg was significantly more effective than placebo over the 6-hour single-dose evaluation (P < 0.05). With multiple dosing, all active-treatment groups had significantly lower least squares mean current and average pain intensities compared with placebo (P < 0.004 and P < 0.005, respectively). The least squares means of the average pain intensity were significantly lower among patients treated with oxymorphone IR 10 mg, oxymorphone IR 20 mg, or oxycodone IR 15 mg compared with those who received placebo (39.7, 35.2, 39.8, and 50.1, respectively; P < 0.005). Discontinuations due to treatment-emergent AEs did not differ significantly between groups: 8.5% (7/82), 17.3% (14/81), 13.3% (11/83), and 12.9% (11/85) in the oxymorphone IR 10-mg, oxymorphone IR 20-mg, oxycodone IR 15-mg, and placebo groups, respectively. The proportions of patients reporting at least 1 treatment-emergent AE were 46.3% (38/82), 51.9% (42/81), and 54.2% (45/83) in the oxymorphone IR 10-mg, oxymorphone IR 20-mg, and oxycodone IR 15-mg groups, respectively, compared with 34.1% (29/85) in the placebo group (P = NS). The fixed-dose design was a study limitation, as it did not allow titration to effect and thus did not mirror clinical practice.

CONCLUSION

In this predominantly female population undergoing abdominal surgery, oxymorphone IR given every 4 to 6 hours for up to 48 hours provided efficacious and tolerable analgesia for moderate to severe pain.

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.

Opioids for persistent noncancer pain

Opioids are extensively used in the management of all types of pain and their use is underpinned by extensive trial evidence and an abundance of practical experience. We are still amassing insight into how they achieve their pain-relieving effects, however, and this understanding becomes more complex as time progresses and shows that opioids are medications with complex and diverse central and peripheral nervous system effects. Despite the 200 years that have passed since the chemical isolation of morphine, every year brings new understanding of the mode of action, propensity to cause side effects, and appropriate clinical use of opioids. This article concentrates on this "new" evidence as disclosed by recent publications.

Interpretation of oral fluid tests for drugs of abuse

Oral fluid testing for drugs of abuse offers significant advantages over urine as a test matrix. Collection can be performed under direct observation with reduced risk of adulteration and substitution. Drugs generally appear in oral fluid by passive diffusion from blood, but also may be deposited in the oral cavity during oral, smoked, and intranasal administration. Drug metabolites also can be detected in oral fluid. Unlike urine testing, there may be a close correspondence between drug and metabolite concentrations in oral fluid and in blood. Interpretation of oral fluid results for drugs of abuse should be an iterative process whereby one considers the test results in the context of program requirements and a broad scientific knowledge of the many factors involved in determining test outcome. This review delineates many of the chemical and metabolic processes involved in the disposition of drugs and metabolites in oral fluid that are important to the appropriate interpretation of oral fluid tests. Chemical, metabolic, kinetic, and analytic parameters are summarized for selected drugs of abuse, and general guidelines are offered for understanding the significance of oral fluid tests.

Efficacy and safety of OPANA ER (oxymorphone extended release) for relief of moderate to severe chronic low back pain in opioid-experienced patients: a 12-week, randomized, double-blind, placebo-controlled study

Opioid-experienced (N = 250) patients with chronic, moderate to severe low back pain (LBP) were converted from their prestudy opioid(s) to an approximately equianalgesic dose of OPANA ER (oxymorphone extended release). Patients continued slow titration, with 56% stabilized within 1 month to a dose of OPANA ER that reduced average pain to <40 mm on a visual analog scale with good tolerability. Stabilized patients (n = 143) were randomized to placebo or their stabilized dose of OPANA ER every 12 hours for a 12-week double-blind period. Pain intensity increased significantly more for patients randomized to placebo than for patients who continued their stabilized dose of OPANA ER; the increase from baseline (at randomization) to final visit was 31.6 mm for placebo versus 8.7 mm with OPANA ER (P < .0001). During double-blind treatment, placebo patients were approximately 8-fold more likely than OPANA ER patients to discontinue because of lack of efficacy (P < .001). Discontinuations as a result of adverse events were similar between groups, 10% with placebo and 11% with OPANA ER. Opioid-related adverse events included constipation (6%), somnolence (3%), and nausea (3%). Fifty-seven percent of opioid-experienced patients with chronic, moderate to severe LBP achieved a stable dose of OPANA ER that was efficacious and generally well-tolerated for up to 12 weeks.

PERSPECTIVE

In a 12-week, double-blind, randomized, placebo-controlled trial in opioid-experienced patients with chronic, moderate to severe LBP, OPANA ER provided efficacious, long-term analgesia and was generally well-tolerated. OPANA ER may provide clinicians with a new treatment option for patients experiencing suboptimal analgesic responses or poor tolerability with other opioids.

Endogenous opiates and behavior: 2005

This paper is the 28th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over a quarter-century of research. It summarizes papers published during 2005 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity, neurophysiology and transmitter release (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); immunological responses (Section 17).

Development and validation of an Opioid Attractiveness Scale: a novel measure of the attractiveness of opioid products to potential abusers

Background

The growing trends in opioid abuse, assessment of the abuse liability of prescription opioid products, and growing efforts by the pharmaceutical industry to develop 'abuse-resistant' formulations highlight a need to understand the features that make one product more 'attractive' than another to potential abusers. We developed a scale to measure the 'attractiveness' of prescription opioids to potential abusers, and used the scale to measure the relative attractiveness of 14 opioid analgesic products.

Methods

First, the concept of attractiveness was empirically defined with a group of prescription opioid abusers and experts in opioid abuse using a process called Concept Mapping. Abuse liability consisted of two components: factors intrinsic to the drug formulation (e.g., speed of onset, duration) and factors extrinsic to drug formulation (e.g., availability, availability of alternatives, cost). A 17-item Opioid Attractiveness Scale (OAS) was constructed, focusing on factors intrinsic to the drug product.

Results

A total of 144 individuals participated in tests of validity and reliability. Internal consistency was excellent (Cronbach's α = 0.85–0.94). Drug rankings based on OAS scores achieved good inter-rater agreement (Kendall's W 0.37, p < 0.001). Agreement on drug OAS scores between the developmental sample and a confirmation sample was good (IntraClass Correlations [ICC] of 0.65–0.69). Global ratings of overall attractiveness of the 14 selected opioid products by substance abuse counselors corresponded with the rankings based on OAS ratings of the abuser group. Finally, substance abuse counselors completed the OAS, yielding a high level of correspondence with ratings by the abuser group (ICC = 0.83, p = 0.002). The OAS differentiated attractiveness among 14 selected pharmaceutical opioid products. OxyContin, Dilaudid, and Percocet were ranked highest (most attractive); Talwin NX and Duragesic were ranked lowest (least attractive).

Conclusion

An initial examination of the psychometric properties of the OAS suggests that it is a valid and reliable scale. The OAS may be useful in providing important guidance on product features that are attractive to potential abusers.

Oxymorphone: a review

Oxymorphone (oxymorphone hydrochloride) (14-hydroxy-dihydromorphinone), a semisynthetic mu-opioid agonist, was first approved by the US Food and Drug Administration in 1959. Oxymorphone is considered a more potent opioid than its parent compound, morphine. Recently, an immediate-release and long-acting oral formulation of this drug was developed that makes oxymorphone a new option in treating moderate to severe pain. This article reviews the pharmacodynamics, pharmacology, and clinical efficacy for this new option in treating moderate to severe pain.