Performance and physiological measures in abuse liability evaluation

Prevalence and Predictors of Driving after Prescription Opioid Use in an Adult ED Sample

Introduction

Prescription opioid use and driving is a public health concern given the risks associated with drugged driving, but the issue remains under-studied. We examined the prevalence and correlates of driving after taking prescription opioids (DAPO) among adults seeking emergency department (ED) treatment.

Methods

Participants (aged 25–60) seeking ED care at a Level I trauma center completed a computerized survey. Validated instruments measured prescription opioid use, driving behaviors, and risky driving. Patients who reported past three-month prescription opioid use and drove at least twice weekly were administered an extended study survey measuring DAPO, depression, pain, and substance use.

Results

Among participants completing the screening survey (n = 756; mean age = 42.8 [standard deviation {SD} =10.4]), 37.8% reported past three-month prescription opioid use (30.8% of whom used daily), and 14.7% reported past three-month DAPO. Of screened participants, 22.5% (n = 170) were eligible for the extended study survey. Unadjusted analyses demonstrated that participants reporting DAPO were more likely to use opioids daily (51.1% vs 15.9%) and had higher rates of opioid misuse (mean Current Opioid Misuse Measure score 3.4 [SD = 3.8] vs 1.1 [SD = 2.1]) chronic pain (80.7% vs 42.7%), and driving after marijuana or alcohol use (mean intoxicated driving score 2.1 [SD = 1.3] vs 0.3 [SD = 0.8]) compared to patients not reporting DAPO (all p<0.001). Adjusting for age, gender, employment, and insurance in a logistic regression model, participants reporting DAPO were more likely to report a chronic pain diagnosis (odds ratio [OR] = 3.77, 95% confidence interval [CI], 1.55–9.17), daily opioid use (OR = 3.81, 95% CI, 1.64–8.85), and higher levels of intoxicated driving (OR = 1.62, 95% CI, 1.07–2.45). Alcohol and marijuana use, depression, and opioid misuse were not associated with DAPO in adjusted analyses.

Conclusion

Nearly one in six adult patients seeking ED care reported DAPO. The ED may be an important site for interventions addressing opioid-related drugged driving.

The gold-standard in preclinical abuse liability testing: It's all relative

All new molecular entities (NMEs) with targeted or indirect effects on the central nervous system (CNS) must be evaluated for their abuse liability as a part of their nonclinical development plan. Inherently key in the drug control review is the term "relative abuse liability". The basis for determination of drug control is critically dependent on the nonclinical assessment of the reinforcing attributes of the NME in animals (rat is the regulatory preferred species) in a standard operant conditioning paradigm. Pharmaceutical representatives without a background in behavioral analysis or operant conditioning models must weigh through conceptually-intriguing language and constructs that accurately convey and communicate the relative potential for abuse to drug regulatory experts in the field. Effective statutory language in the preclinical assessment of relative abuse liabilities for schedule control status reviews must be 1) specific; 2) concise; 3) familiar to the regulators; 4) unambiguous; 5) constructive; and 6) formalized with respect to both international and national drug control policies. In this review we attempt to define and highlight the importance of the statutory language used to report self-administration study results to both parties engaged in NDA approval process.

Core outcome measures for opioid abuse liability laboratory assessment studies in humans: IMMPACT recommendations

A critical component in development of opioid analgesics is assessment of their abuse liability (AL). Standardization of approaches and measures used in assessing AL have the potential to facilitate comparisons across studies, research laboratories, and drugs. The goal of this report is to provide consensus recommendations regarding core outcome measures for assessing the abuse potential of opioid medications in humans in a controlled laboratory setting. Although many of the recommended measures are appropriate for assessing the AL of medications from other drug classes, the focus here is on opioid medications because they present unique risks from both physiological (e.g., respiratory depression, physical dependence) and public health (e.g., individuals in pain) perspectives. A brief historical perspective on AL testing is provided, and those measures that can be considered primary and secondary outcomes and possible additional outcomes in AL assessment are then discussed. These outcome measures include the following: subjective effects (some of which comprise the primary outcome measures, including drug liking; physiological responses; drug self-administration behavior; and cognitive and psychomotor performance. Before presenting recommendations for standardized approaches and measures to be used in AL assessments, the appropriateness of using these measures in clinical trials with patients in pain is discussed.

Effects of 24 hours of tobacco withdrawal and subsequent tobacco smoking among low and high sensation seekers

INTRODUCTION

Previous studies have indicated that high sensation seekers are more sensitive to the reinforcing effects of nicotine, initiate smoking at an earlier age, and smoke greater amounts of cigarettes. This study examined the influence of sensation-seeking status on tobacco smoking following deprivation in regular tobacco users.

METHODS

Twenty healthy tobacco-smoking volunteers with low or high impulsive sensation-seeking subscale scores completed 2 consecutive test days per week for 3 consecutive weeks. Each week, a range of self-report, performance, and cardiovascular assessments were completed during ad libitum smoking on Day 1 and before and after the paced smoking of a tobacco cigarette containing 0.05, 0.6, or 0.9 mg of nicotine following 24 hr of tobacco deprivation on Day 2. In addition, self-administration behavior was analyzed during a 2-hr free access period after the initial tobacco administration.

RESULTS

In high sensation seekers, tobacco smoking independent of nicotine yield ameliorated deprivation effects, whereas amelioration of deprivation effects was dependent on nicotine yield among low sensation seekers. However, this effect was limited to a small subset of measures. Subsequent cigarette self-administration increased in a nicotine-dependent manner for high sensation seekers only.

CONCLUSIONS

Compared with low sensation seekers, high sensation seekers were more sensitive to the withdrawal relieving effects of nonnicotine components of smoking following 24 hr of deprivation on selective measures and more sensitive to nicotine yield during subsequent tobacco self-administration. These results are consistent with studies suggesting that factors driving tobacco dependence may vary as a function of sensation-seeking status.

Performance and subjective effects of diazepam and d-amphetamine in high and low sensation seekers

Although sensation-seeking status is associated with age of initiation and amount of drug use among adolescents, and sensitivity to the behavioral and reinforcing effects of drugs among young adults, it is unclear whether sensation-seeking status among adolescents is predictive of sensitivity to the pharmacological effects of drugs (i.e. abuse potential) as adults. This study examined the acute behavioral effects of oral diazepam and d-amphetamine in young adults, ages 18-21 years, who had consistently scored in the highest or lowest third of their grade-based cohort on a modified Sensation Seeking Scale that was completed annually between ages 10 and 14 years. Healthy participants completed 16 7.5-h test days, with test days separated by a minimum of 48 h. Each day, assessments consisting of computer task performance, verbal report of drug effects, and cardiovascular measures were completed 0, 50, 110, 170, 230, and 290 min after drug administration. Placebo and three active doses of diazepam and d-amphetamine (2.5, 5.0 and 10.0 mg/70 kg) were tested under double-blind conditions according to a randomized-block design. Typical stimulant and sedative effects were obtained with d-amphetamine and diazepam, respectively. Drug effects varied as a function of sensation-seeking status, with magnitude of effects on cardiovascular function, task performance, and report of positive drug effects being greater among high sensation seekers, and report of negative drug effects being greater among low sensation seekers. Adolescents who report high levels of sensation seeking on a consistent basis are more sensitive to pharmacological effects of stimulant and sedative drugs that are associated with abuse potential as young adults.

Individual differences in drug abuse vulnerability: d-amphetamine and sensation-seeking status

RATIONALE

While the personality dimensions of novelty seeking and sensation seeking are associated with drug abuse vulnerability, the mechanisms associated with this vulnerability remain obscure.

OBJECTIVE

This study examined the behavioral effects of d-amphetamine in healthy volunteers scoring in the upper and lower quartiles based on age- and gender-adjusted population norms on the impulsive Sensation-Seeking Scale (SSS) of the Zuckerman-Kuhlman personality questionnaire (ZKPQ).

METHOD

Participants completed 7-day outpatient studies examining the subjective, performance, and cardiovascular effects of d-amphetamine (0, 7.5, and 15 mg/70 kg, p.o.) under double-blind conditions according to a randomized block design. Performance tasks included behavioral measures of impulsivity, including attention, inhibition, and risk-taking behavior.

RESULTS

No differences in baseline performance or d-amphetamine effects on measures of attention, inhibition, and risk-taking behavior were observed. High impulsive sensation seekers reported greater increases on several subjective report measures associated with drug abuse potential, including visual analog scales feel drug, like drug, and high.

CONCLUSIONS

Healthy adults scoring in the top quartile on the population of the impulsive SSS of the ZKPQ may be vulnerable to the abuse potential of d-amphetamine.

FMRI Measurement of CNS Responses to Naloxone Infusion and Subsequent Mild Noxious Thermal Stimuli in Healthy Volunteers

The aims of this study were to assess the effects of a μ-opioid antagonist, naloxone, on endogenous opioid systems and to evaluate the effect of naloxone on the CNS response to mild noxious heat. Doubled-blinded experiments were performed in a cross-over design in 10 healthy male volunteers. Functional magnetic resonance imaging (fMRI) data were collected before and during the infusion and also during thermal stimuli. Increased signal was observed in a number of cortical and subcortical brain regions for naloxone versus saline infusion. Cortical activation was induced in regions including cingulate, prefrontal cortex, and insula. Subcortical regions showing increased signal change included hippocampus and entorhinal cortex. A 46°C stimulus delivered to the back of the hand induced an overall increase in activation in a number of regions in the naloxone group that were not seen in the saline group (e.g., insula, orbitofrontal cortex, thalamus, and hippocampus). These results show that naloxone, even in the absence of psychophysical effects, produces activation in several brain regions that are known to have high levels of μ-opioid receptors and may be involved in endogenous analgesia. Our study is an example of how fMRI can measure subtle changes in brain activation induced by pharmacological agents without cognitive effects.

Guidelines and methodological reviews concerning drug abuse liability assessment

Regulatory control of drugs with abuse liability is an important component of drug control policy and is believed to help prevent nonmedical use. To be maximally effective, this requires a scientific assessment of abuse liability of drugs considered for regulatory control. These assessments have relied extensively on laboratory-based animal and human testing, but also utilize information from clinical trials, actual abuse and other sources. Here, we discuss recommendations and guidelines that have been proposed for abuse liability assessment and describe important review papers and conference proceedings that have addressed this matter, focusing primarily on drugs with medical usefulness. Historically, there is substantial consensus about how to approach abuse liability evaluation of drugs with actions similar to those of abused opiates, stimulants, depressants, and to a somewhat lesser extent, cannabinoids and hallucinogens, and much of what has been recommended for abuse potential assessment in the past remains valid and useful. On the other hand, novel CNS-active medications which cannot be readily classified with these traditional drugs of abuse are increasingly under development. In addition, advances in the science of abuse liability assessment need to be incorporated into future guidelines and recommendations on this subject. Developers of new medications need guidance on how to utilize scientific research to maximize therapeutic benefit while minimizing risk for abuse. Thus, another goal of this review has been to identify areas where critical thinking and new guideline development are needed.

Effects of opioids on driving ability

Driving has been regarded as an activity of daily living that is important in maintaining a person's independence in the community, access to employment, and social activities. Many patients, however, using opioid medications on a regular basis (Chronic Opioid Analgesic Therapy: COAT) to ameliorate their intractable pain have been restricted from driving out of concern that skills would be impaired and driving safety compromised by these medications. Yet there are no driving studies which have explored the effects of using opioid analgesics for an extended period of time. This pilot study was designed to determine the effects of medically prescribed, stable opioid use on the driving abilities of patients with persistent, nonmalignant pain. Sixteen patients with chronic nonmalignant pain on COAT, who met criteria for participation in the study, underwent a comprehensive off-road driving evaluation using measures which have been shown to be sensitive in predicting on-road driving performance. The evaluation consisted of a pre-driver evaluation (PDE), a simulator evaluation (SDE), and behavioral observation during simulator performance. Patients in the COAT group were compared to a historical control group of 327 cerebrally compromised patients (CComp) who had undergone the same evaluation and then passed an on-road, behind-the-wheel evaluation (BTW Pass; n = 162) or failed (BTW Fail; n = 165). Results revealed that COAT patients generally outperformed the CComp patients as a group by equaling or exceeding PDE and SDE scores of the BTW Fail patients as well as the BTW Pass patients on all measures that differentiated the groups. Notably, COAT patients had a relatively poorer performance than CComp patients on specific neuropsychometric tests in the PDE; however, the differences were not statistically significant and did not imply a systematic pattern of scores that reflected domain-specific deficits. Behaviorally, COAT patients were generally superior to CComp patients, also; however, COAT patients had greater difficulty in following instructions and as well as a tendency toward impulsivity, like the BTW fail group. While there was general support for the notion that COAT did not significantly impair the perception, cognition, coordination, and behavior measured in off-road tests that have been regarded as requisite for on-road driving, methodological problems may limit the generalizability of results and recommendations are made for research beyond a pilot study.

Laboratory measures of methylphenidate effects in cocaine-dependent patients receiving treatment

Two experiments examined the effects of methylphenidate in male and female patients enrolled in an outpatient treatment program for primary cocaine dependence. The first study was a component of a double-blind efficacy trial wherein 57 patients were first tested in a human laboratory for their initial responsiveness to medication. Patients were randomly assigned to receive either placebo or methylphenidate treatment and received their first dose in the human laboratory environment before continuing in outpatient treatment. Methylphenidate was given as a 20-mg sustained-release dose (twice daily) plus an additional 5-mg immediate-release dose combined with the morning dose. Methylphenidate increased heart rate and subjective ratings; however, the subjective effects were primarily of a "dysphoric" nature, and significant effects were limited to increases in anxiety, depression, and anger on the Profile of Mood States; shaky/jittery ratings on a visual analog scale; and dysphoria on the lysergic acid diethylamide (LSD) scale of the Addiction Research Center Inventory. Methylphenidate did not increase cocaine craving nor ratings suggesting abuse potential (i.e., Morphine-Benzedrine Group or drug-liking scores, etc.). None of the drug effects observed in the human laboratory was of clinical concern, and no subject was precluded from continuing in the outpatient study. After outpatient treatment completion, 12 patients were brought back into a second double-blind human laboratory study in which three doses (15, 30, and 60 mg) of immediate-release methylphenidate were administered in an ascending series preceded and followed by placebo. Methylphenidate produced dose-related increases in heart rate, subjective ratings of shaky/jittery, and LSD/dysphoria without significantly altering cocaine craving or stimulant euphoria ratings. These results suggest that stimulant substitution-type approaches to the treatment of cocaine dependence are not necessarily contraindicated because of cardiovascular toxicity or medication abuse potential. However, they also suggest that the subjective effects of methylphenidate may not be positive enough for an adequate replacement approach.