Paul A. Nuzzo

The Relative Abuse Liability of Oral Oxycodone, Hydrocodone and Hydromorphone Assessed in Prescription Opioid Abusers

Abuse of prescription opioids has risen precipitously in the United States. Few controlled comparisons of the abuse liability of the most commonly abused opioids have been conducted. This outpatient study employed a double-blind, randomized, within-subject, placebo-controlled design to examine the relative abuse potential and potency of oral oxycodone (10, 20 and 40 mg), hydrocodone (15, 30 and 45 mg), hydromorphone (10, 17.5 and 25mg) and placebo. Healthy adult volunteers (n=9) with sporadic prescription opioid abuse participated in 11 experimental sessions (6.5h in duration) conducted in a hospital setting. All three opioids produced a typical mu opioid agonist profile of subjective (increased ratings of liking, good effects, high and opiate symptoms), observer-rated, and physiological effects (miosis, modest respiratory depression, exophoria and decrements in visual threshold discrimination) that were generally dose-related. Valid relative potency assays revealed that oxycodone was roughly equipotent to or slightly more potent than hydrocodone. Hydromorphone was only modestly more potent (less than two-fold) than either hydrocodone or oxycodone, which is inconsistent with prior estimates arising from analgesic studies. These data suggest that the abuse liability profile and relative potency of these three commonly used opioids do not differ substantially from one another and suggest that analgesic potencies may not accurately reflect relative differences in abuse liability of prescription opioids.

An Internet-based abstinence reinforcement smoking cessation intervention in rural smokers

The implementation of cigarette smoking abstinence reinforcement programs may be hindered by the time intensive burden placed on patients and treatment providers. The use of remote monitoring and reinforcement of smoking abstinence may enhance the accessibility and acceptability of this intervention, particularly in rural areas where transportation can be unreliable and treatment providers distant. This study determined the effectiveness of an Internet-based abstinence reinforcement intervention in initiating and maintaining smoking abstinence in rural smokers. Sixty-eight smokers were enrolled to evaluate the efficacy of an Internet-based smoking cessation program. During the 6-week intervention period, all participants were asked to record 2 videos of breath carbon monoxide (CO) samples daily. Participants also typed the value of their CO readings into web-based software that provided feedback and reinforcement based on their smoking status. Participants (n=35) in the Abstinence Contingent (AC) group received monetary incentives contingent on recent smoking abstinence (i.e., CO of 4 parts per million or below). Participants (n=33) in the Yoked Control (YC) group received monetary incentives independent of smoking status. Participants in the AC group were significantly more likely than the YC group to post negative CO samples on the study website (OR=4.56; 95% CI=2.18-9.52). Participants assigned to AC were also significantly more likely to achieve some level of continuous abstinence over the 6-week intervention compared to those assigned to YC. These results demonstrate the feasibility and short-term efficacy of delivering reinforcement for smoking abstinence over the Internet to rural populations.

Abuse liability and reinforcing efficacy of oral tramadol in humans

BACKGROUND Tramadol, a monoaminergic reuptake inhibitor, is hepatically metabolized to an opioid agonist (M1). This atypical analgesic is generally considered to have limited abuse liability. Recent reports of its abuse have increased in the U.S., leading to more stringent regulation in some states, but not nationally. The purpose of this study was to examine the relative abuse liability and reinforcing efficacy of tramadol in comparison to a high (oxycodone) and low efficacy (codeine) opioid agonist. METHODS Nine healthy, non-dependent prescription opioid abusers (6 male and 3 female) participated in this within-subject, randomized, double blind, placebo-controlled study. Participants completed 14 paired sessions (7 sample and 7 self-administration). During each sample session, an oral dose of tramadol (200 and 400 mg), oxycodone (20 and 40 mg), codeine (100 and 200 mg) or placebo was administered, and a full array of abuse liability measures was collected. During self-administration sessions, volunteers were given the opportunity to work (via progressive ratio) for the sample dose or money. RESULTS All active doses were self-administered; placebo engendered no responding. The high doses of tramadol and oxycodone were readily self-administered (70%, 59% of available drug, respectively); lower doses and both codeine doses maintained intermediate levels of drug taking. All three drugs dose-dependently increased measures indicative of abuse liability, relative to placebo; however, the magnitude and time course of these and other pharmacodynamic effects varied qualitatively across drugs. CONCLUSIONS This study demonstrates that, like other mu opioids, higher doses of tramadol function as reinforcers in opioid abusers, providing new empirical data for regulatory evaluation.

Cocaine abuse versus cocaine dependence: Cocaine self-administration and pharmacodynamic response in the human laboratory

Cocaine has high abuse liability but only a subset of individuals who experiment with it develop dependence. The DSM-IV (APA. Diagnostic and Statistical Manual of Mental Disorders DSM-IV-R. American Psychiatric Association, Washington, DC, 2000) provides criteria for diagnosing cocaine abuse and cocaine dependence as distinct disorders- the latter characterized by additional symptoms related to loss of control over drug use. In this study, two groups of cocaine users (n=8/group), matched on demographic factors and length of cocaine use history and meeting criteria for either cocaine abuse (CocAb) or cocaine dependence (CocDep), were compared on (1) measures related to impulsivity and sensation seeking, (2) response to experimenter-administered cocaine (0, 12.5, 25 and 50mg/70 kg, i.v.), and (3) cocaine self-administration using a Relapse Choice and a Progressive Ratio Procedure (0, 12.5 and 25mg/70 kg, i.v.). Groups did not differ on impulsivity or sensation seeking scores. After experimenter-administered cocaine, the CocAb group reported feeling more suspicious and observers rated them significantly higher on unpleasant effects (e.g., irritability, difficulty concentrating). In contrast, the CocDep group reported significantly greater desire for cocaine, which was sustained over the course of the study, and gave higher street value estimates for cocaine (p<0.05). While cocaine self-administration was dose-related and generally comparable across the two procedures, the CocDep users chose to take significantly more cocaine than the CocAb users. These data suggest that, while regular long-term users of cocaine with cocaine abuse or dependence diagnoses cannot be distinguished by trait measures related to impulsivity, they do exhibit significant differences with regard to cocaine-directed behavior and response to cocaine administration.

Oral Cannabidiol does not Alter the Subjective, Reinforcing or Cardiovascular Effects of Smoked Cannabis

Cannabidiol (CBD), a constituent of cannabis with few psychoactive effects, has been reported in some studies to attenuate certain aspects of Δ9-tetrahydrocannabinol (THC) intoxication. However, most studies have tested only one dose of CBD in combination with one dose of oral THC, making it difficult to assess the nature of this interaction. Further, the effect of oral CBD on smoked cannabis administration is unknown. The objective of this multi-site, randomized, double-blind, within-subject laboratory study was to assess the influence of CBD (0, 200, 400, 800 mg, p.o.) pretreatment on the reinforcing, subjective, cognitive, and physiological effects of smoked cannabis (0.01 (inactive), 5.30–5.80% THC). Non-treatment-seeking, healthy cannabis smokers (n=31; 17M, 14 F) completed eight outpatient sessions. CBD was administered 90 min prior to cannabis administration. The behavioral and cardiovascular effects of cannabis were measured at baseline and repeatedly throughout the session. A subset of participants (n=8) completed an additional session to measure plasma CBD concentrations after administration of the highest CBD dose (800 mg). Under placebo CBD conditions, active cannabis (1) was self-administered by significantly more participants than placebo cannabis and (2) produced significant, time-dependent increases in ratings of ‘High’, ‘Good Effect’, ratings of the cannabis cigarette (eg, strength, liking), and heart rate relative to inactive cannabis. CBD, which alone produced no significant psychoactive or cardiovascular effects, did not significantly alter any of these outcomes. Cannabis self-administration, subjective effects, and cannabis ratings did not vary as a function of CBD dose relative to placebo capsules. These findings suggest that oral CBD does not reduce the reinforcing, physiological, or positive subjective effects of smoked cannabis.

Contingent incentives reduce cigarette smoking among pregnant, methadone-maintained women: Results of an initial feasibility and efficacy randomized clinical trial

AIMS This study examined the feasibility and efficacy of behavioral incentives for reducing cigarette smoking among pregnant methadone-maintained patients. DESIGN Participants (n = 102) were assigned randomly to: (i) contingent behavioral incentives (CBI: n = 42); (ii) non-contingent behavioral incentives (NCBI: n = 28); or (iii) treatment as usual (TAU: n = 32). SETTING Study procedures were implemented at the Center for Addiction and Pregnancy in Baltimore, MD. PARTICIPANTS Study participants were pregnant, methadone-maintained women enrolled in substance use disorder treatment. MEASUREMENTS Baseline carbon monoxide (CO) levels were calculated for each participant. Subsequently, breath samples were tested three times weekly to measure changes in smoking behavior. CBI participants received incentives for target reductions from baseline: any reduction (week 1); 10% reduction (weeks 2-4), 25% reduction (weeks 5-7), 50% reduction (weeks 8-9), 75% reduction (week 10-11); and abstinence [CO < 4 parts per million (p.p.m.)] (week 12 until delivery). NCBI participants received incentives independent of smoking CO measurement results. TAU participants received no incentives, the standard treatment at the program. FINDINGS CBI condition participants submitted significantly lower mean CO values than the NCBI and TAU conditions over the course of the intervention (P < 0.0001). Nearly half (48%) of the CBI participants met the 75% smoking reduction target and one-third (31%) met the abstinence target at week 12. In contrast, none of the NCBI met either the 75% or abstinence targets. Only 2% of the TAU participants met the 75% reduction and none of the TAU participants met the abstinence targets. These smoking behavior reductions did not yield significant differences in birth outcomes. CONCLUSIONS Cigarette smoking may be reduced significantly among pregnant, methadone-maintained women through the use of contingent reinforcement for gradual reductions in breath carbon monoxide levels.

Employment-based reinforcement of adherence to oral naltrexone treatment in unemployed injection drug users.

Oral naltrexone has high potential for use as a relapse prevention pharmacotherapy for opiate dependence yet suffers from notoriously poor adherence. This study evaluated whether entry to a therapeutic workplace could reinforce adherence with oral naltrexone. Opiate-dependent and cocaine-using injection drug users were detoxified, inducted onto oral naltrexone, and randomly assigned to a contingency (n = 35) or prescription (n = 32) group for a 26-week period. Contingency participants were required to ingest naltrexone under staff observation to gain access to the therapeutic workplace. Prescription participants received a take-home supply of naltrexone and could access the workplace independent of naltrexone ingestion. Primary outcome measures were percent of urine samples positive for naltrexone at 30-day assessments and negative for opiates and cocaine at 30-day assessments. Contingency participants provided significantly more urine samples that were positive for naltrexone compared with prescription participants (72% vs. 21%, p < .01); however, no effect of experimental group was observed on percent opiate-negative (71% vs. 60%, p = .19.) or cocaine-negative (56% vs. 53%, p = .82) samples in the contingency and prescription groups, respectively. Opiate-positive samples were significantly more likely to occur in conjunction with cocaine (p < .001) and when not protected by naltrexone (p < .02), independent of experimental group. Overall, these results show that contingent access to a therapeutic workplace significantly promoted adherence to oral naltrexone, and that the majority of opiate use occurred in conjunction with cocaine use, suggesting that untreated cocaine use may limit the effectiveness of oral naltrexone in promoting opiate abstinence.

Atomoxetine does not alter cocaine use in cocaine dependent individuals: A double blind randomized trial

BACKGROUND Cocaine abuse continues to be a significant public health problem associated with morbidity and mortality. To date, no pharmacotherapeutic approach has proven effective for treating cocaine use disorders. Preclinical and clinical evidence suggests that noradrenergic activity may play a role in mediating some effects of cocaine and may be a rational target for treatment. METHODS This double blind, placebo-controlled randomized, parallel group, 12-week outpatient clinical trial enrolled cocaine dependent individuals seeking treatment to examine the potential efficacy of the selective norepinephrine reuptake inhibitor, atomoxetine (80 mg/day; p.o.; n = 25), compared to placebo (n = 25). Subjects were initially stratified on cocaine use (< 15 days or ≥ 15 days of the last 30), age and race using urn randomization. Attendance, medication adherence and study compliance were reinforced with contingency management, and weekly counseling was offered. An array of measures (vital signs, laboratory chemistries, cognitive and psychomotor tests, cocaine craving and urine samples for drug testing) was collected throughout the study and at follow-up. RESULTS Survival analysis revealed no differences in study retention between the two groups, with approximately 56% of subjects completing the 12-week study (Cox analysis χ(2) = .72; p = .40; Hazard Ratio 1.48 [95% CI 0.62-3.39]). GEE analysis of the proportion of urine samples positive for benzoylecgonine, a cocaine metabolite, revealed no differences between the atomoxetine and placebo groups (χ(2) = 0.2, p = .66; OR = 0.89 [95% CI 0.41-1.74]). Atomoxetine was generally well tolerated in this population. CONCLUSIONS These data provide no support for the utility of atomoxetine in the treatment of cocaine dependence.

Efficacy of continuing medical education to reduce the risk of buprenorphine diversion.

As office-based opioid dependence treatment (OBOT) has grown in the United States, postmarketing surveillance data reveal increased reports of buprenorphine misuse and diversion. It is important that doctors understand buprenorphine clinical pharmacology and engage in practices to decrease risk of misuse, diversion, and other adverse events. This study evaluated the efficacy of continuing medical education (CME) in two U.S. regions with surveillance signals of buprenorphine misuse/diversion. Four surveys (before, on-site, and 1 and 3 months post CME) evaluated physician characteristics, practice behaviors, and buprenorphine pharmacology and legislative knowledge. The results show that physicians had limited addictions training. Knowledge and practice behaviors significantly improved after the CME, which should enhance the quality of OBOT and may decrease risk of buprenorphine misuse and diversion from their practices. Mandatory CME targeting OBOT-certified physicians could have a positive impact on patient and public health outcomes.

Effects of the NK1 antagonist, aprepitant, on response to oral and intranasal oxycodone in prescription opioid abusers

Pre‐clinical studies suggest that the neurokinin‐1 (NK1) receptor may modulate the response to opioids, with NK1 inactivation leading to decreased opioid reinforcement, tolerance and withdrawal. Aprepitant is a selective NK1 antagonist currently marketed for clinical use as an anti‐emetic. This 6‐week in‐patient study used a randomized, double‐blind, double‐dummy, within‐subject, crossover design. Subjects (n = 8; 6 male/2 female) were healthy, adult volunteers who provided subjective and objective evidence of current prescription opioid abuse (without physical dependence) and underwent careful medical and psychiatric screening. Fifteen experimental conditions, consisting of one aprepitant dose (0, 40 and 200 mg, p.o. given as a 2‐hour pre‐treatment) in combination with one oxycodone dose [placebo, oral (20 and 40 mg/70 kg) and intranasal (15 and 30 mg/70 kg)], were examined. Sessions were conducted at least 48‐hour apart and multi‐dimensional measures were collected repeatedly throughout the 6‐hour session duration. Oxycodone, by both routes of administration, produced significant dose‐related effects on the predicted measures (e.g. subjective measures of abuse liability, respiratory depression and miosis). Pre‐treatment with aprepitant (200 mg) significantly enhanced ratings of oxycodone subjective effects related to euphoria and liking and doubled the street value estimates for the highest test doses of oxycodone by both routes. Some objective measures (respiratory function, observer‐rated opioid agonist effects) were similarly enhanced by pre‐treatment with the highest dose of aprepitant. All dose combinations were safely tolerated. These findings are discussed in the context of the potential utility of NK1 antagonists in the treatment of opioid use disorders.