Smoked cannabis reduces peak cocaine plasma levels and subjective effects in a controlled drug administration study of polysubstance use in men.

BACKGROUND: Despite the high prevalence of polysubstance use, outcomes and potential risks associated with common drug combinations are not well characterized. Many individuals who use cocaine also use cannabis, yet little is known about how interactions between the two drugs might contribute to continued co-use. METHODS: The aim of this double-blind, placebo-controlled study was to determine the physiological and subjective effects of smoked cannabis with smoked cocaine, to identify variables that may contribute to the continued use of this drug combination. Healthy, non-treatment seeking volunteers who reported smoking both cocaine and cannabis (N = 9, all males) completed a 13-day inpatient protocol. On session days, cannabis [0.0 or 5.6 % tetrahydrocannabinol (THC)] was administered 28 min prior to cocaine (0, 12, or 25 mg). Dependent measures included pharmacokinetic assessment of THC and cocaine and their respective metabolites, in addition to subjective and cardiovascular effects. RESULTS: Active cannabis (5.6 % THC) increased plasma levels of THC and the metabolite 11-nor-9-carboxy-Δ9-THC (THCCOOH), as well as subjective ratings of cannabis effects and heart rate relative to inactive cannabis. Cocaine dose-dependently increased plasma cocaine and metabolites and subjective ratings of cocaine effects. Active cannabis pre-treatment decreased plasma levels of cocaine and metabolites. Furthermore, active cannabis attenuated cocaine-related reductions in 'Hunger' and 'Calm.' CONCLUSIONS: Cannabis pre-treatment altered the subjective experience of smoked cocaine and reduced peak plasma levels of cocaine. Future studies should explore additional doses of each drug and whether these changes also impact cocaine's reinforcing effects.

The effects of acute oral naltrexone pretreatment on the abuse potential of intranasal methamphetamine, and the relationship between reward/punishment sensitivity and methamphetamine's effects.

One potential medication for treating methamphetamine use disorder is the opioid antagonist naltrexone (NLTX). Despite encouraging preclinical findings, the results of clinical studies have been mixed. The primary aim of the current trial was to examine the effects of acute NLTX pretreatment on the subjective and reinforcing effects of intranasal methamphetamine. Nonmedical psychostimulant users completed outpatient testing sessions in which they received oral placebo (0 mg) or NLTX (50 mg) before intranasal methamphetamine (30 mg/70 kg). Primary outcome measures were peak positive subjective effects (e.g. drug 'Liking') assessed on a visual analog scale (0-100), and methamphetamine self-administration using an operant self-administration task. Participants also completed a probabilistic categorization task to assess reward and punishment learning sensitivity. Complete data were available from 13 male and 1 transgender (male-to-female) participant (age: 33.4 ± 7.6 years). Intranasal methamphetamine significantly increased subjective ratings of drug 'Liking', 'Good Effect' and 'High' from baseline (P's < 0.01), but did not significantly vary as a function of placebo or NLTX pretreatment. Similarly, methamphetamine self-administration did not vary between the placebo and NLTX pretreatment conditions. This sample did not demonstrate a significant 'bias' in learning from positive and negative outcomes (i.e. reward and punishment sensitivity), and reward/punishment sensitivity was not correlated with the effects of methamphetamine or the effects of NLTX on methamphetamine. The current study argues against the use of NLTX as a stand-alone medication for treating methamphetamine use disorder.

Relative potency of intravenous oxymorphone compared to other µ opioid agonists in humans - pilot study outcomes.

AIMS: Intravenous (IV) misuse of the µ opioid analgesic oxymorphone has caused significant public health harms; however, no controlled data on its IV abuse potential are available. The primary aims of this pilot study were to directly compare IV oxymorphone to IV oxycodone, morphine, and hydromorphone on a subjective measure of drug liking and to assess relative potency. METHODS: Participants (n = 6) with opioid use disorder, physical dependence, and current IV use completed this two-site, within-subject, double-blind, placebo-controlled, inpatient pilot study. During each session, one IV dose (mg/70 kg) was administered: oxymorphone (1.8, 3.2, 5.6, 10, 18, 32), hydromorphone (1.8, 3.2, 5.6, 10, 18), oxycodone (18, 32, 56), morphine (18, 32), and placebo. Data were collected before and for 6 h after dosing. Primary outcomes included safety/physiological effects, subjective reports of drug liking, and relative potency estimates. RESULTS: All active test drugs produced prototypical, dose-related µ opioid agonist effects (e.g., miosis). Oxymorphone was more potent than the comparator opioids on several measures, including drug liking and respiratory depression (p < 0.05). Across abuse-related subjective outcomes, oxymorphone was 2.3-2.8-fold more potent than hydromorphone and 12.5-14-fold more potent than oxycodone (p < 0.05). CONCLUSIONS: Despite the relatively small sample size, this pilot study detected robust oxymorphone effects. Oxymorphone was far more potent than the comparator opioids, particularly on abuse potential outcomes. Overall, these findings may help explain surveillance reports that demonstrate, after adjusting for prescription availability, oxymorphone is injected at the highest frequency, relative to other prescription opioids.

Effects of lorcaserin on oxycodone self-administration and subjective responses in participants with opioid use disorder.

BACKGROUND: Lorcaserin, a high-affinity 5-HT2C receptor agonist approved for treating obesity, decreased self-administration of oxycodone and cue-induced reinstatement of drug-seeking behavior in preclinical studies. The current investigation is the first clinical trial to evaluate the ability of lorcaserin to alter the reinforcing and subjective effects of oxycodone. METHODS: In this 7-week inpatient trial, 12 non-treatment-seeking volunteers (11 males) with moderate-to-severe opioid use disorder were detoxified from opioids. In a randomized cross-over fashion, participants were first stabilized on lorcaserin (10 mg BID) or placebo (0 mg BID). Participants underwent a two-week testing period during which the reinforcing and subjective effects of intranasal oxycodone were examined in verbal choice, cue-exposure, and progressive-ratio choice sessions. The two testing weeks were identical with the exception that during the first week, active oxycodone (10 mg) was available during verbal choice (self-administration) sessions, and during the second week placebo oxycodone was available. Subsequently, participants were stabilized on the other medication condition (placebo or lorcaserin) and underwent the same testing procedures again. RESULTS: Lorcaserin did not alter oxycodone self-administration. However, lorcaserin had a trend to increase "wanting heroin" when oxycodone was available, and to accentuate oxycodone-induced miosis. CONCLUSION: Under the current experimental conditions, lorcaserin at a dose of 10 mg BID did not reliably decrease the abuse liability of oxycodone, even though the study was sufficiently powered (≥80 %) to detect clinically meaningful differences in the main outcome variables between the placebo and active lorcaserin condition. Future research could explore a wider dose range of lorcaserin and oxycodone.

Assessing the contribution of opioid- and dopamine-related genetic polymorphisms to the abuse liability of oxycodone.

BACKGROUND: Attempts to identify opioid users at increased risk of escalating to opioid use disorder have had limited success. Data from a variety of sources suggest that genetic variation may mediate the subjective response to opioid drugs, and therefore contribute to their abuse potential. The goal of the current study was to observe the relationship between select genetic polymorphisms and the subjective effects of oxycodone under controlled clinical laboratory conditions. METHODS: Non-dependent, volunteers with some history of prescription opioid exposure (N = 36) provided a blood sample for analyses of variations in the genes that encode for the µ-, κ- and δ-opioid receptors, and the dopamine metabolizing enzyme, catechol-O-methyltransferase (COMT). Participants then completed a single laboratory test session to evaluate the subjective and analgesic effects of oral oxycodone (0, 10, and 20 mg, cumulative dose = 30 mg). RESULTS: Oxycodone produced typical µ-opioid receptor agonist effects, such as miosis, and decreased pain perception. Oxycodone also produced dose-dependent increases in positive subjective responses such as: drug "Liking" and "Good Effect." Genetic variants in the µ- (rs6848893) and δ-opioid receptor (rs581111) influenced the responses to oxycodone administration. Additionally, self-reported "Stimulated" effects of oxycodone varied significantly as a function of COMT rs4680 genotype. DISCUSSION: The current study shows that the euphoric and stimulating effects of oxycodone can vary as a function of genetic variation. Though the relationship between the stimulating effects of opioids and their abuse liability is not well established, we know that the ability of opioids to provide intense feelings of pleasure is a significant motivator for continued use. If replicated, specific genetic variants may be useful in predicting who is at increased risk of developing maladaptive patterns of use following medical exposure to opioid analgesics.

Sex differences in stress reactivity after intranasal oxytocin in recreational cannabis users.

Cannabis is the most widely used illicit drugs and the changing legal, political and cultural climate will likely increase cannabis use further. One factor that may underlie the transition from recreational use to problematic use is stress. The hormone oxytocin (OXT) modulates stress and may have therapeutic efficacy for substance use disorders, but few studies have examined OXT in cannabis users. Another factor is sex; although more men smoke cannabis, the transition from recreational to problematic use is faster in women. Using a within-subjects design, the effects of intranasal (i.n.) oxytocin (OXT; 40 IU) administration on stress reactivity (using the Trier Social Stress Test; TSST) and cannabis (5.6% THC) self-administration was assessed in recreational cannabis using men (n = 31) and women (n = 32) relative to i.n. placebo (PBO) and no-stress (NST) conditions. The TSST produced expected subjective and cardiovascular effects compared to the NST. However, in the i.n. OXT-TSST condition, positive subjective effects were lower and negative subjective effects were higher in women compared to PBO administration and compared to men. Further, latency to self-administer cannabis was longer in women than men and women self-administered less cannabis than men regardless of stress condition. There were no differences in cannabis craving as a function of sex, stress, or medication. These results suggest that OXT administration may lead to greater stress reactivity in recreational cannabis users, particularly women, and support growing evidence that sex differences should be carefully considered when examining the therapeutic potential of OXT.

The PPARγ Agonist Pioglitazone Fails to Alter the Abuse Potential of Heroin, But Does Reduce Heroin Craving and Anxiety.

Possibly through its effects on glia, the peroxisome proliferator-activated gamma receptor (PPARγ) agonist pioglitazone (PIO) has been shown to alter the effects of heroin in preclinical models. Until now, these results have not been assessed in humans. Heroin-dependent participants were randomized to either active (45 mg, n = 14) or placebo (0 mg, n = 16) PIO maintenance for the duration of the three-week study. After stabilization on buprenorphine (8 mg), participants began a two-week testing period. On the first to fourth test days, participants could self-administer drug or money by making verbal choices for either option. On the fifth day, active heroin and money were administered and participants could work to receive heroin or money using a progressive ratio choice procedure. Test days 6-10 were identical to test days 1-5 with the exception that, during one of the test weeks, placebo was available on the first four days, and during the other week heroin was available. PIO failed to alter the reinforcing or positive subjective effects of heroin, but it did reduce heroin craving and overall anxiety. Although we were unable to replicate the robust effects found in preclinical models, these data provide an indication of drug effects that deserves further exploration.

Pioglitazone, a PPARγ agonist, reduces nicotine craving in humans, with marginal effects on abuse potential.

Possibly through their actions upon glia, peroxisome proliferator-activated receptor agonists (PPAR) have been shown to alter the abuse potential of addictive drugs in several preclinical models. The current study extends this research into the human laboratory as the first clinical study into the effects of the PPAR gamma agonist, pioglitazone, on the abuse potential of nicotine. Heavy smokers were recruited for this 3-week study. Upon admission, participants were randomized to either active (45mg, n=14) or placebo (0mg, n=13) PIO maintenance conditions for the duration of the study. After 5-7days of stabilization on a 7mg nicotine patch, participants began laboratory testing. On the 1st-4th test days, participants could self-administer cigarettes or receive money by making verbal choices for either option. On the 5th day, participants were administered 10 puffs of their usual brand of cigarette in the morning and later chose between smoking and money by making finger presses on a computer mouse in a progressive ratio self-administration task. Later on the 5th day participants also underwent a smoking cue exposure session. The 8th-11th test days were identical to the 1st-4th test days with the exception that during one of the test weeks de-nicotinized cigarettes were available, and during the other nicotinized cigarettes were available. Nicotinized cigarettes were always administered on the 5th and 12th days. On some measures PIO increased indicators of abuse potential, though this effect was typically not statistically significant. However, PIO did significantly reduce measures of craving.

Abuse liability of intravenous buprenorphine vs. buprenorphine/naloxone: Importance of absolute naloxone amount.

BACKGROUND: This study sought to determine the relative importance of a range of Bup/Nx doses compared to Bup alone in producing subjective and reinforcing effects. METHODS: Heroin-using volunteers (n=13) were transitioned onto daily oral hydromorphone (40mg). Laboratory sessions assessed the reinforcing and subjective effects of intravenous (IV) doses of Bup (1.51, 2.16, 6.15, and 8.64mg) and Bup/Nx (1.51/0.44, 2.16/0.61, 6.15/1.71, and 8.64/2.44mg). Placebo (Pbo), heroin (25mg) and Nx (0.3mg) were tested as neutral, positive, and negative controls, respectively. RESULTS: IV Bup alone was self-administered substantially less than IV heroin, though the two largest doses of Bup produced positive subjective effects, drug "Liking" (0-100mm), which were comparable to heroin (mean difference: Heroin vs Bup 6.15mg: -3.4mm, Heroin vs Bup 8.64mg: -11.3mm). All indicators of abuse potential seen with IV Bup alone were substantially decreased with the addition of Nx. All Bup/Nx combinations produced ratings of aversive effects, "Bad", which were comparable to, or greater than IV, Nx. On three of the four measures of aversive effects, the largest difference is seen with the 8.64 vs 8.64/2.44 condition. CONCLUSIONS: This study further demonstrates the ability of the Bup/Nx combination to deter IV use. Although none of the Bup/Nx combinations showed indications of abuse potential, formulations with larger absolute Nx, may be less abusable as they precipitate a greater degree of withdrawal.

Effects of Ibudilast on the Subjective, Reinforcing, and Analgesic Effects of Oxycodone in Recently Detoxified Adults with Opioid Dependence.

Ibudilast, a nonselective phosphodiesterase inhibitor, is used clinically in Asia for the treatment of asthma and poststroke dizziness. Recent preclinical studies have suggested that it also inhibits glial cell activation in rodents, and may alter opioid-mediated effects, including analgesia and withdrawal symptoms. The effects of ibudilast on the abuse potential of opioids in humans are largely unknown. The present study was designed to examine the influence of ibudilast on subjective (including drug craving), reinforcing, and analgesic effects of oxycodone in human volunteers diagnosed with opioid dependence (equivalent to moderate-severe opioid use disorder). Non-treatment-seeking opioid-dependent male volunteers (n=11) underwent an in-patient detoxification with morphine, followed by maintenance on placebo (0 mg b.i.d.) and active ibudilast (50 mg b.i.d.). Under each maintenance dose, six experimental sample and choice sessions were completed involving oral oxycodone administration (0, 15, and 30 mg/70 kg, p.o.). Subjective effects of oxycodone and drug craving were measured with visual analog scales (VAS) and a Drug Effects Questionnaire. The cold pressor test was used to produce pain, and a modified progressive-ratio choice procedure was used to measure the reinforcing effects of oxycodone. Under the active ibudilast condition compared with the placebo condition, ratings of drug liking following 15 mg of oxycodone were decreased significantly. The mean drug breakpoint value was also significantly lower in the active vs the placebo ibudilast condition under the 15 mg oxycodone condition, but not significantly lower under the 30 mg oxycodone condition. Heroin craving was significantly reduced under active ibudilast vs placebo, and similar effects were observed for tobacco and cocaine craving. Furthermore, mean subjective ratings of pain were lower in the active ibudilast condition. Our data suggest that ibudilast may be useful for treating opioid use disorders and it may enhance the analgesic effects of oxycodone.

The effects of pioglitazone, a PPARγ receptor agonist, on the abuse liability of oxycodone among nondependent opioid users.

AIMS: Activation of PPARγ by pioglitazone (PIO) has shown some efficacy in attenuating addictive-like responses in laboratory animals. The ability of PIO to alter the effects of opioids in humans has not been characterized in a controlled laboratory setting. The proposed investigation sought to examine the effects of PIO on the subjective, analgesic, physiological and cognitive effects of oxycodone (OXY). METHODS: During this investigation, nondependent prescription opioid abusers (N=17 completers) were maintained for 2-3weeks on ascending daily doses of PIO (0mg, 15mg, 45mg) prior to completing a laboratory session assessing the aforementioned effects of OXY [using a within-session cumulative dosing procedure (0, 10, and 20mg, cumulative dose=30mg)]. RESULTS: OXY produced typical mu opioid agonist effects: miosis, decreased pain perception, and decreased respiratory rate. OXY also produced dose-dependent increases in positive subjective responses. Yet, ratings such as: drug "liking," "high," and "good drug effect," were not significantly altered as a function of PIO maintenance dose. DISCUSSION: These data suggest that PIO may not be useful for reducing the abuse liability of OXY. These data were obtained with a sample of nondependent opioid users and therefore may not be applicable to dependent populations or to other opioids. Although PIO failed to alter the abuse liability of OXY, the interaction between glia and opioid receptors is not well understood so the possibility remains that medications that interact with glia in other ways may show more promise.

The effects of ibudilast, a glial activation inhibitor, on opioid withdrawal symptoms in opioid-dependent volunteers.

Glial activation is hypothesized to contribute directly to opioid withdrawal. This study investigated the dose-dependent effects of a glial cell modulator, ibudilast, on withdrawal symptoms in opioid-dependent volunteers after abrupt discontinuation of morphine administration. Non-treatment-seeking heroin-dependent volunteers (n = 31) completed the in-patient, double-blind, placebo-controlled, within-subject and between-group study. Volunteers were maintained on morphine (30 mg, QID) for 14 days and placebo (0 mg, QID) for the last 7 days of the 3-week study. Volunteers also received placebo (0 mg, PO, BID) capsules on days 1-7. On days 8-21, volunteers were randomized to receive ibudilast (20 or 40 mg, PO, BID) or placebo capsules. Subjective and clinical ratings of withdrawal symptoms were completed daily using daily using the Subjective Opioid Withdrawal Scale (SOWS) and Clinical Opioid Withdrawal Scale (COWS). Medication side effects were also monitored. Relative to the first 2 weeks, all groups exhibited withdrawal during the third week as assessed by the SOWS and COWS (P ≤ 0.0001). Although overall SOWS scores did not differ between groups, exploratory analyses pooling the two ibudilast groups demonstrated that they had lower ratings of withdrawal symptoms on SOWS items ('anxious,' 'perspiring,' 'restless,' 'stomach cramps') during detoxification relative to the placebo group. Ibudilast was well tolerated; no serious adverse events occurred during the study. Pharmacological modulation of glial activity with ibudilast decreased some subjective ratings of opioid withdrawal symptoms. These exploratory findings are the first to demonstrate the potential clinical utility of glial modulators for treating opioid withdrawal in humans.

Abuse potential of intranasal buprenorphine versus buprenorphine/naloxone in buprenorphine-maintained heroin users.

In spite of the clinical utility of buprenorphine, parenteral abuse of this medication has been reported in several laboratory investigations and in the real world. Studies have demonstrated lower abuse liability of the buprenorphine/naloxone combination relative to buprenorphine alone. However, clinical research has not yet examined the utility of the combined formulation to deter intranasal use in a buprenorphine-maintained population. Heroin-using volunteers (n = 12) lived in the hospital for 8-9 weeks and were maintained on each of three sublingual buprenorphine doses (2, 8, 24 mg). Under each maintenance dose, participants completed laboratory sessions during which the reinforcing and subjective effects of intranasal doses of buprenorphine (8, 16 mg), buprenorphine/naloxone (8/2, 8/8, 8/16, 16/4 mg) and controls (placebo, heroin 100 mg, naloxone 4 mg) were assessed. Intranasal buprenorphine alone typically produced increases in positive subjective effects and the 8 mg dose was self-administered above the level of placebo. The addition of naloxone dose dependently reduced positive subjective effects and increased aversive effects. No buprenorphine/naloxone combination dose was self-administered significantly more than placebo. These data suggest that within a buprenorphine-dependent population, intranasal buprenorphine/naloxone has reduced abuse potential in comparison to buprenorphine alone. These data strongly argue in favor of buprenorphine/naloxone rather than buprenorphine alone as the more reasonable option for managing the risk of buprenorphine misuse.

Sex differences among opioid-abusing patients with chronic pain in a clinical trial.

BACKGROUND: The characteristics of patients with co-occurring chronic pain and prescription opioid abuse have not been well described, and even less is known about differences between men and women in this population. OBJECTIVES: This study evaluated sex differences in the demographic, diagnostic, and behavioral attributes of patients with chronic pain and opioid abuse. METHODS: Data were collected via self-report and semistructured clinical interviews from 162 patients (120 men and 42 women) who screened for a study investigating the abuse liability of prescription opioids. RESULTS: There were no differences between men and women in age, race, education, marital status, or employment status. Participants had used prescription opioids for 5.4 ± 6.7 years. The majority of participants (60%) had low back pain in addition to opioid dependence as defined by the Diagnostic and Statistical Manual of Mental Disorders Fourth Edition. More women reported more arthritic pain than men, but otherwise there were no differences in types of pain. Pain exerted a greater effect in women on mood, walking ability, and social relations. Men reported more of certain aberrant behaviors, including abuse of alcohol or illicit drugs, unauthorized dose increases, contact with street culture, and being arrested by police. Women were more depressed than men. CONCLUSIONS: The demographic profile of opioid-abusing patients with chronic pain presenting for treatment in a clinical trial was similar between sexes; however, some important differences were observed. Women reported more psychiatric comorbidity and endorsed greater pain-related physical and social impairment. Men reported more aberrant behaviors. These differences suggest that men with chronic pain and opioid abuse/dependence may benefit by closer monitoring of aberrant behaviors whereas women may benefit from closer attention paid to physical and psychological effects of pain.

Comparison of a drug versus money and drug versus drug self-administration choice procedure with oxycodone and morphine in opioid addicts.

This double-blind, placebo-controlled study investigated the effects of oral morphine (0, 45, 135 mg/70 kg) and oral oxycodone (0, 15, 45 mg/70 kg) on buprenorphine-maintained opioid addicts. As a 3: 1 morphine : oxycodone oral dose ratio yielded equivalent subjective and physiological effects in nondependent individuals, this ratio was used in the present study. Two self-administration laboratory procedures - that is, a drug versus money and a drug versus drug procedure - were assessed. Study participants (N=12) lived in the hospital and were maintained on 4 mg/day sublingual buprenorphine. When participants chose between drug and money, money was preferred over all drug doses; only high-dose oxycodone was self-administered more than placebo. When participants chose between drug and drug, both drugs were chosen more than placebo, high doses of each drug were chosen over low doses, and high-dose oxycodone was preferred over high-dose morphine. The subjective, performance-impairing, and miotic effects of high-dose oxycodone were generally greater than those of high-dose morphine. The study demonstrated that a 3: 1 oral dose ratio of morphine : oxycodone was not equipotent in buprenorphine-dependent individuals. Both self-administration procedures were effective for assessing the relative reinforcing effects of drugs; preference for one procedure should be driven by the specific research question of interest.

Effects of acute oral naltrexone on the subjective and physiological effects of oral D-amphetamine and smoked cocaine in cocaine abusers.

Despite the prevalent worldwide abuse of stimulants, such as amphetamines and cocaine, no medications are currently approved for treating this serious public health problem. Both preclinical and clinical studies suggest that the opioid antagonist naltrexone (NTX) is effective in reducing the abuse liability of amphetamine, raising the question of whether similar positive findings would be obtained for cocaine. The purpose of this study was to evaluate the ability of oral NTX to alter the cardiovascular and subjective effects of D-amphetamine (D-AMPH) and cocaine (COC). Non-treatment-seeking COC users (N=12) completed this 3-week inpatient, randomized, crossover study. Participants received 0, 12.5, or 50 mg oral NTX 60 min before active or placebo stimulant administration during 10 separate laboratory sessions. Oral AMPH (0, 10, and 20 mg; or all placebo) was administered in ascending order within a laboratory session using a 60-min interdose interval. Smoked COC (0, 12.5, 25, and 50 mg; or all placebo) was administered in ascending order within a laboratory session using a 14-min interdose interval. Active COC and AMPH produced dose-related increases in cardiovascular function that were of comparable magnitude. In contrast, COC, but not AMPH, produced dose-related increases in several subjective measures of positive drug effect (eg, high, liking, and willingness to pay for the drug). NTX did not alter the cardiovascular effects of AMPH or COC. NTX also did not alter positive subjective ratings after COC administration, but it did significantly reduce ratings of craving for COC and tobacco during COC sessions. These results show that (1) oral AMPH produces minimal abuse-related subjective responses in COC smokers, and (2) NTX reduces craving for COC and tobacco during COC sessions. Future studies should continue to evaluate NTX as a potential anti-craving medication for COC dependence.

Buprenorphine/naloxone as a promising therapeutic option for opioid abusing patients with chronic pain: reduction of pain, opioid withdrawal symptoms, and abuse liability of oral oxycodone.

Few studies have examined abuse of prescription opioids among individuals with chronic pain under buprenorphine/naloxone (Bup/Nx) maintenance. The current 7-week inpatient study assessed oral oxycodone self-administration by patients with chronic pain who had a history of opioid abuse. Participants (n=25) were transitioned from their preadmission prescribed opioid to Bup/Nx. All of the participants were tested under each of the sublingual Bup/Nx maintenance doses (2/0.5, 8/2 or 16/4 mg) in random order. During each maintenance period, participants could self-administer oxycodone orally (0, 10, 20, 40 or 60 mg prescription opioids) or receive money during laboratory sessions. Drug choice (percentage) was the primary dependent variable. Subjective ratings of clinical pain and withdrawal symptoms also were measured. Mann-Whitney tests compared percentage of drug choice for each active oxycodone dose to placebo. Logistic regression analyses identified correlates of oxycodone preference, defined as 60% or greater choice of oxycodone compared to money. Pain was significantly reduced while participants were maintained on Bup/Nx compared to preadmission ratings. No differences in percentage drug choice were observed between the active oxycodone doses and placebo under each Bup/Nx maintenance dose. However, factors associated with oxycodone preference were lower Bup/Nx maintenance dose, more withdrawal symptoms and more pain. These data suggest that Bup/Nx was effective in reducing pain and supplemental oxycodone use. Importantly, adequate management of pain and withdrawal symptoms by Bup/Nx may reduce oxycodone preference in this population.

A comparison among tapentadol tamper-resistant formulations (TRF) and OxyContin® (non-TRF) in prescription opioid abusers.

AIMS: To examine whether tamper-resistant formulations (TRFs) of tapentadol hydrochloride extended-release (ER) 50 mg (TAP50) and tapentadol hydrochloride 250 mg (TAP250) could be converted into forms amenable to intranasal (study 1) or intravenous abuse (study 2). DESIGN: Randomized, repeated-measures study designs were employed. A non-TRF of OxyContin® 40 mg (OXY40) served as a positive control. No drug was taken in either study. SETTING: The studies took place in an out-patient setting in New York, NY. PARTICIPANTS: Twenty-five experienced, healthy ER oxycodone abusers participated in each study. MEASUREMENTS: The primary outcome for study 1 was the percentage of participants who indicated that they would snort the tampered tablets, while the primary outcome for study 2 was the percentage yield of active drug in solution. Other descriptive variables, such as time spent manipulating the tablets, were also examined to characterize tampering behaviors more clearly. FINDINGS: Tampered TRF tablets were less desirable than the tampered OXY40 tablets. Few individuals were willing to snort the TRF particles (TAP50: 24%, TAP250: 16%; OXY40: 100% P < 0.001). There was less drug extracted from the TAP50 tablet than from the OXY40 tablet (3.52 versus 37.02%, P = 0.008), and no samples from the TAP250 tablets contained analyzable solutions of the drug. It took participants longer to tamper with the TAPs (study 1: TAP50 versus OXY40, P < 0.01; TAP250 versus OXY40, P < 0.01; study 2: TAP250 versus OXY40, P < 0.05). CONCLUSIONS: Tamper-resistant formulations of taptentadol (pain relief) tablets do not appear to be well-liked by individuals who tamper regularly with extended-release oxycodone tablets. Employing tamper-resistant technology may be a promising approach towards reducing the abuse potential of tapentadol extended-release.

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.

Effects of repeated oxycodone administration on its analgesic and subjective effects in normal, healthy volunteers.

Tolerance to the analgesic effects of opioids has been demonstrated in laboratory animals after repeated drug administration; yet, this effect has been studied less frequently under controlled laboratory conditions in humans. This within-subject, double-blind, placebo-controlled study was designed to determine whether tolerance developed to the analgesic, subjective, and physiological effects of the commonly prescribed opioid oxycodone when it was administered daily for 5 days. The effects of oxycodone (0, 5, and 20 mg/70 kg, orally) were compared, using a within-session cumulative dosing procedure, on the first and fifth days of the 'daily' dosing phase to assess for tolerance; active oxycodone was administered on the second and fourth days of the daily dosing phase. Changes in the effects of oxycodone were also compared when the medication was only administered on the first and the fifth day of a 5-day 'intermittent' dosing phase; placebo medication was administered on the second and fourth days of the intermittent dosing phase. A 9-day 'washout' period occurred between phases during which no medication was administered. Healthy volunteers (N=10) with no history of drug dependence or current drug use participated in this outpatient study. Analgesia was assessed using the cold pressor test, pain and drug effects were measured using a variety of questionnaires, and pupil diameter was monitored as an index of physiological effects. When administered daily, no differences were observed in oxycodone-induced analgesia between the first and the fifth days, but tolerance did develop to some of the positive subjective effects of oxycodone. In contrast, oxycodone-induced analgesia and participant ratings of some positive subjective drug effects were greater on the fifth compared with the first day of the intermittent dosing phase. No differences in the miotic effects of oxycodone between the first and the fifth days of either dosing phase were detected. Although obtained under limited experimental conditions, these findings suggest that tolerance may not develop to the analgesic effects of therapeutic doses of oxycodone under short-term daily dosing conditions, even though some of its subjective effects may decrease. These data also suggest that intermittent administration may enhance the analgesic effects of oxycodone, while also increasing some of the drug's positive subjective effects related to abuse liability.