Abuse risks and routes of administration of different prescription opioid compounds and formulations

Elevated acetaminophen concentration measured after nasal insufflation of Percocet®

BACKGROUND

Prescription opioid products are often formulated with acetaminophen, but the pharmacokinetics of nasally administered acetaminophen are poorly characterized. We report a case of a potentially toxic acetaminophen concentration after nasal insufflation of oxycodone/acetaminophen tablets.

CASE REPORT

A 38-year-old female presented to the emergency department after 2 days of nasally insufflating a total of 50 oxycodone/acetaminophen 5/325 mg tablets. On day 3, she was evaluated for nausea and pharyngitis. She denied oral ingestion of the drug. The initial acetaminophen concentration was 14 μg/mL, although the patient had not insufflated any medication in approximately 24 h. Initial AST and ALT were normal. The patient was treated with a 21-h course of intravenous N-acetylcysteine. On hospital day 2, the measured acetaminophen concentration was < 10 μg/mL and the patient's liver enzymes remained within normal limits.

CONCLUSIONS

The pharmacokinetics of nasally administered acetaminophen have not been well studied, yet there is potential for significant exposure with prescription opioid abuse. Clinicians should be vigilant in evaluating patients for toxicity due to adjunct medications formulated in narcotic pain preparations used by routes other than ingestion.

Assessment of pharmacodynamic effects following oral administration of crushed morphine sulfate and naltrexone hydrochloride extended-release capsules compared with crushed morphine sulfate controlled-release tablets and placebo in nondependent recreational opioid users

OBJECTIVES

To compare the pharmacodynamic effects, including self-reports of "drug liking" and "high," of crushed morphine sulfate and naltrexone hydrochloride extended-release capsules (MSN), crushed morphine sulfate controlled-release (CR) tablets, and placebo in an abuse potential study.

DESIGN

Randomized, double-blind, placebo-controlled, three-way crossover study.

SETTING

Single-center.

SUBJECTS

Nondependent recreational opioid users.

INTERVENTIONS

Orally administered crushed MSN (120-mg morphine sulfate and 4.8-mg naltrexone hydrochloride), crushed 120-mg morphine sulfate CR, and placebo.

OUTCOME MEASURES

Subjective ratings (100-point visual analog scales) of positive drug effects (drug liking, high, good effects, take drug again, and overall drug liking), any effects, and negative effects (bad effects, feel sick, nausea, sleepy, and dizzy), along with pupillometry, pharmacokinetic (PK), and safety assessments.

RESULTS

Crushed morphine sulfate CR significantly increased ratings of all positive subjective measures relative to placebo (P < 0.0001). Crushed MSN significantly decreased all positive subjective ratings compared with morphine sulfate CR (P ≤ 0.005), but significantly increased ratings compared with placebo (P < 0.03). Peak pupil diameter was significantly larger for MSN than morphine sulfate (P < 0.0001). PK analysis of morphine plasma concentrations indicated that Cmax was significantly lower and tmax significantly longer for crushed MSN compared with crushed morphine sulfate CR. Plasma concentrations of naltrexone and 6-β-naltrexol were present following crushed MSN.

CONCLUSIONS

This study demonstrated that when crushed and administered orally to nondependent recreational opioid users, MSN was associated with significantly lower scores on all positive subjective measures including drug liking and high, and significantly less pupil constriction compared with crushed morphine sulfate CR.

Update on tamper-resistant drug formulations

An expert panel convened in 2005 by the College on Problems of Drug Dependence (CPDD) to consider strategies to reduce the risk of prescription medication abuse concluded that drug formulation plays a significant role in determining risk of abuse. Efforts on the part of the pharmaceutical industry to develop drugs that deter abuse have focused primarily on opioid formulations resistant to common forms of tampering, most notably crushing or dissolving the tablet to accelerate release. Several opioid formulations developed to be tamper resistant have been approved, but the US Food and Drug Administration has not approved explicit label claims of abuse deterrence and has stated that any such claim will require substantial postmarketing data. Drug development efforts in this area raise questions about the relative impact of abuse-deterrent formulations, not only on individuals who might abuse a medication, but also on patients who are compliant with therapy. This review discusses progress since the 2005 CPDD meeting with an emphasis on opioids. Articles cited in the review were identified via a PubMed search covering the period between January 1, 2000, and October 5, 2011. Scientific work presented by the authors and their colleagues at meetings held through May 2012 also was included. Published literature suggests that development of abuse-deterrent products will require broad public health support and continued encouragement from regulatory authorities so that such products will become the expected standard of care for certain drug classes.

Likeability and abuse liability of commonly prescribed opioids

INTRODUCTION

Nonmedical use of prescription opioid analgesics is associated with epidemic levels of morbidity and mortality. There are several factors that affect the abuse liability of the various opioids, including likability or the pleasurable subjective effects. Due to rising public health concerns over escalating prescription opioid abuse, we sought to examine the literature about abuse liability with a specific focus on likability studies.

METHODS

A search of EMBASE and MEDLINE databases identified articles that described the comparative likeability and/or abuse potential of hydrocodone and oxycodone relative to each other and/or of either one to morphine. After an assessment of study quality using the Oxford/Jadad scale, relevant details such as demographics, study design, and outcome measures were compiled into an evidence table.

RESULTS

We identified nine studies that met inclusion criteria. All were double-blinded, randomized, placebo-controlled crossover studies and scored 5 out of 5 Jadad scale. There was no consistent clinically significant difference between abuse liability of morphine and hydrocodone. Oxycodone demonstrated high abuse liability on the basis of its high likability scores and a relative lack of negative subjective effects.

CONCLUSION

Oral oxycodone has an elevated abuse liability profile compared to oral morphine and hydrocodone.

The implications of tamper-resistant formulations for opioid rotation

Because rates of both opioid prescribing and opioid abuse have increased, drug companies have responded by considering strategies to make opioid formulations less attractive for abuse without compromising safety or efficacy for patients with legitimate pain management needs. The emergence of tamper-resistant opioid formulations is intended to deter abuse by creating obstacles to crushing or dissolving opioid tablets and capsules. At present, 2 long-acting and 1 immediate-release (IR) opioids are available in tamper-resistant formulations. Oxycodone controlled-release and oxymorphone extended-release tablets have each been reformulated with a hardened matrix that resists crushing or dissolution in liquids, making them difficult to prepare for nasal insufflation or intravenous use. Oxycodone IR has been reformulated with aversive ingredients that create nasal discomfort if the tablet is crushed and insufflated. Tamper-resistant opioid formulations are likely to be selected for patients who are identified as being at risk for abuse. However, patients vary in their response to individual opioids and may require rotation to a series of alternative opioids before finding one that is effective and sufficiently well tolerated. With only a few tamper-resistant opioid formulations currently available, switching and rotation may become difficult. As a result, patients who do not respond to a tamper-resistant opioid formulation or experience intolerable adverse events may require rotation to a formulation without tampering safeguards. Prescribers will need to be on guard for patients who may make false claims of poor response or adverse events to avoid tamper-resistant opioid formulations. Moreover, prescribers need to be aware of any tamper-resistance mechanisms that may affect efficacy or tolerability in patients with legitimate pain management needs compared with formulations without tampering safeguards.

Reduced antinociception of opioids in rats and mice by vaccination with immunogens containing oxycodone and hydrocodone haptens

Prescription opioids abuse and associated deaths are an emerging concern in the USA. Vaccination against prescription opioids may provide an alternative to pharmacotherapy. An oxycodone hapten containing a tetraglycine linker at the C6 position (6OXY(Gly)(4)OH) conjugated to keyhole limpet hemocyanin (KLH) has shown early proof-of-efficacy in rodents as a candidate immunogen (6OXY(Gly)(4)-KLH) for the treatment of oxycodone abuse. In this study, oxycodone-based and hydrocodone-based haptens were conjugated to KLH to generate immunogens that would recognize both oxycodone and hydrocodone. Vaccination with 6OXY(Gly)(4)-KLH increased drug binding in serum, reduced drug distribution to brain, and blunted analgesia for both oxycodone and hydrocodone. An analogous C6-linked hydrocodone vaccine blocked hydrocodone effects but less so than 6OXY(Gly)(4)-KLH. C8-Linked hydrocodone immunogens had only limited efficacy. Amide conjugation showed higher haptenation ratios and greater efficacy than thioether conjugation to maleimide activated KLH (mKLH). The 6OXY(Gly)(4)-KLH vaccine may be used for treatment of prescription opioid abuse.

Comparison of opioid doctor shopping for tapentadol and oxycodone: a cohort study

Obtaining opioids from multiple prescribers, known as doctor shopping, is 1 example of opioid abuse and diversion. The dual mechanism of action of tapentadol could make tapentadol less likely to be abused than other opioids. The aim of this retrospective cohort study was to compare the risk of shopping behavior between tapentadol immediate release (IR) and oxycodone IR. Subjects exposed to tapentadol or oxycodone with no recent opioid use were included and followed for 1 year. The primary outcome was the proportion of subjects who developed shopping behavior defined as subjects who had opioid prescriptions written by >1 prescriber with ≥1 day of overlap filled at ≥3 pharmacies. The opioids involved in the shopping episodes were assessed. A total of 112,821 subjects were exposed to oxycodone and 42,940 to tapentadol. Shopping behavior was seen in .8% of the subjects in the oxycodone group and in .2% of the subjects in the tapentadol group, for an adjusted odds ratio of 3.5 (95% confidence interval, 2.8 to 4.4). In the oxycodone group, 28.0% of the shopping events involved exclusively oxycodone, whereas in the tapentadol group, .6% of the shopping events involved exclusively tapentadol. Results suggest that the risk of shopping behavior is substantially lower with tapentadol than with oxycodone.

PERSPECTIVE

The risk of opioid doctor shopping, ie, obtaining opioid prescriptions from multiple prescribers, is lower with tapentadol than with oxycodone.

Abuse rates and routes of administration of reformulated extended-release oxycodone: initial findings from a sentinel surveillance sample of individuals assessed for substance abuse treatment

Oxycodone hydrochloride controlled-release, also known as extended-release oxycodone (ER oxycodone), was reformulated with physicochemical barriers to crushing and dissolving intended to reduce abuse through nonoral routes of administration (ROAs) that require tampering (eg, injecting and snorting). Manufacturer shipments of original ER oxycodone (OC) stopped on August 5, 2010, and reformulated ER oxycodone (ORF) shipments started August 9, 2010. A sentinel surveillance sample of 140,496 individuals assessed for substance abuse treatment at 357 U.S. centers between June 1, 2009, and March 31, 2012, was examined for prevalence and prescription-adjusted prevalence rates of past-30-day abuse via any route, as well as abuse through oral, nonoral, and specific ROAs for ER oxycodone and comparators (ER morphine and ER oxymorphone) before and after ORF introduction. Significant reductions occurred for 8 outcome measures of ORF versus OC historically. Abuse of ORF was 41% lower (95% CI: -44 to -37) than historical abuse for OC, with oral abuse 17% lower (95% CI: -23 to -10) and nonoral abuse 66% lower (95% CI: -69 to -63). Significant reductions were not observed for comparators. Observations were consistent with the goals of a tamper resistant formulation for an opioid. Further research is needed to determine the persistence and generalizability of these findings.

PERSPECTIVE

This article presents preliminary findings indicating that 8 outcome measures of abuse of a reformulated ER oxycodone were lower than that for original ER oxycodone historically, particularly through nonoral ROAs that require tampering (ie, injection, snorting, smoking), in a sentinel sample of individuals assessed for substance use problems for treatment planning.

Assessment of a formulation designed to be crush-resistant in prescription opioid abusers

BACKGROUND

The extent of prescription opioid abuse has led to the development of formulations that are difficult to crush. The purpose of the present studies was to examine whether experienced prescription opioid abusers (individuals using prescription opioids for non-medical purposes regardless of how they were obtained) were able to prepare a formulation of oxymorphone hydrochloride ER 40 mg designed to be crush-resistant (DCR) for intranasal (study 1) or intravenous abuse (study 2), utilizing a non-crush-resistant formulation of oxymorphone (40 mg; OXM) as a positive control.

METHODS

No drug was administered in these studies. Participants were provided with DCR and OXM tablets in random order and asked to prepare them for abuse with tools/solutions that they had previously requested. The primary outcome for study 1 was particle size distribution, and the primary outcome for study 2 was percent yield of active drug in the extracts. Other descriptive variables were examined to better understand potential responses to these formulations.

RESULTS

Fewer DCR than OXM particles were smaller than 1.705 mm (9.8% vs. 97.7%), and thus appropriate for analyses. Percent yield of active drug in extract was low and did not differ between the two formulations (DCR: 1.95%; OXM: 1.29%). Most participants were not willing to snort (92%) or inject (84%) the tampered products. Participants indicated that they found less relative value in the DCR than the OXM formulation across both studies.

CONCLUSIONS

These data suggest that the oxymorphone DCR formulations may be a promising technology for reducing opioid abuse.

Measuring online endorsement of prescription opioids abuse: an integrative methodology

PURPOSE

The ability to track prescription opioid abusers' endorsement of compounds may be valuable in forecasting abuser's preferences. We developed a metric, referred to as the Endorsement Ratio (ERo), to explore the feasibility of quantifying the sentiment expressed by opioid abusers who post online about prescription opioid products.

METHODS

Internet posts written between April 1, 2010 and March 31, 2011 and related to six prescription opioid compounds (oxycodone ER, hydrocodone, hydromorphone, oxymorphone, morphine ER, and tramadol) were identified and qualitatively coded. A mixed effects multinomial logistic regression was employed to model the probability of observing endorsing, discouraging, mixed, or unclear messages per compound. Endorsement-to-discouragement ratio (ERo) and ratio of endorsement-to-discouragement ratios (RERo) were estimated for each compound.

RESULTS

In the study sample of 12 838 Internet posts, a ranking of endorsement could be established, with oxymorphone as most endorsed (ERo = 7.39), followed by hydromorphone (ERo = 5.02), hydrocodone (ERo = 3.53), oxycodone ER (ERo = 3.23), morphine ER (ERo = 2.71), and tramadol (ERo = 1.76). Relative rankings of products required that route of administration be considered.

CONCLUSIONS

This study expands existing Internet monitoring approaches by developing a metric to estimate the endorsement of specific prescription opioid compounds as viewed through the lens of Internet communities. Route of administration must be taken into account when examining preferences of drug abusers for various products. This study did not assess whether the novel metric is valid with respect to classification of abuse rates of different drugs. Further studies examining external validation studies are warranted.

Co-administration of morphine and oxycodone vaccines reduces the distribution of 6-monoacetylmorphine and oxycodone to brain in rats

Opioid conjugate vaccines have shown promise in animal models as a potential treatment for opioid addiction. Individual vaccines are quite specific and each targets only a limited number of structurally similar opioids. Since opioid users can switch or transition between opioids, we studied a bivalent immunization strategy of combining 2 vaccines that could target several of the most commonly abused opioids; heroin, oxycodone and their active metabolites. Morphine (M) and oxycodone (OXY) haptens were conjugated to keyhole limpet hemocyanin (KLH) through tetraglycine (Gly)(4) linkers at the C6 position. Immunization of rats with M-KLH alone produced high titers of antibodies directed against heroin, 6-monoacetylmorphine (6-MAM) and morphine. Immunization with OXY-KLH produced high titers of antibodies against oxycodone and oxymorphone. Immunization with the bivalent vaccine produced consistently high antibody titers against both immunogens. Bivalent vaccine antibody titers against the individual immunogens were higher than with the monovalent vaccines alone owing, at least in part, to cross-reactivity of the antibodies. Administration of a single concurrent intravenous dose of 6-MAM and oxycodone to rats immunized with the bivalent vaccine increased 6-MAM, morphine and oxycodone retention in serum and reduced the distribution of 6-MAM and oxycodone to brain. Vaccine efficacy correlated with serum antibody titers for both monovalent vaccines, alone or in combination. Efficacy of the individual vaccines was not compromised by their combined use. Consistent with the enhanced titers in the bivalent group, a trend toward enhanced pharmacokinetic efficacy with the bivalent vaccine was observed. These data support the possibility of co-administering two or more opioid vaccines concurrently to target multiple abusable opioids without compromising the immunogenicity or efficacy of the individual components.

An update in options for the treatment of pain: a review of new opioid formulations

In the past 2 decades, there has been a significant increase in the use of opioids for the management of chronic nonmalignant pain. This increase in usage has led to concerns of misuse and abuse of opioids. Also, many of the available opioid options were previously only available as oral tablets or capsules, further limiting treatment options for health care providers. Several new opioid formulations have been developed to address and prevent the misuse and abuse of opioids via tampering in the United States. In addition, alternative delivery systems have been developed to provide physicians with more options to provide adequate pain management for those with chronic pain. This article reviews new opioid options for the treatment of pain management and requirements of the Risk Evaluation and Mitigation Strategies program.