Alcohol pretreatment increases preference for cocaine over monetary reinforcement

Ethanol inhibits dopamine uptake via organic cation transporter 3: Implications for ethanol and cocaine co-abuse

Concurrent cocaine and alcohol use is among the most frequent drug combination, and among the most dangerous in terms of deleterious outcomes. Cocaine increases extracellular monoamines by blocking dopamine (DA), norepinephrine (NE) and serotonin (5-HT) transporters (DAT, NET and SERT, respectively). Likewise, ethanol also increases extracellular monoamines, however evidence suggests that ethanol does so independently of DAT, NET and SERT. Organic cation transporter 3 (OCT3) is an emergent key player in the regulation of monoamine signaling. Using a battery of in vitro, in vivo electrochemical, and behavioral approaches, as well as wild-type and constitutive OCT3 knockout mice, we show that ethanol's actions to inhibit monoamine uptake are dependent on OCT3. These findings provide a novel mechanistic basis whereby ethanol enhances the neurochemical and behavioral effects of cocaine and encourage further research into OCT3 as a target for therapeutic intervention in the treatment of ethanol and ethanol/cocaine use disorders.

Addiction is driven by excessive goal-directed drug choice under negative affect: translational critique of habit and compulsion theory

Drug addiction may be a goal-directed choice driven by excessive drug value in negative affective states, a habit driven by strong stimulus-response associations, or a compulsion driven by insensitivity to costs imposed on drug seeking. Laboratory animal and human evidence for these three theories is evaluated. Excessive goal theory is supported by dependence severity being associated with greater drug choice/economic demand. Drug choice is demonstrably goal-directed (driven by the expected value of the drug) and can be augmented by stress/negative mood induction and withdrawal-effects amplified in those with psychiatric symptoms and drug use coping motives. Furthermore, psychiatric symptoms confer risk of dependence, and coping motives mediate this risk. Habit theory of addiction has weaker support. Habitual behaviour seen in drug-exposed animals often does not occur in complex decision scenarios, or where responding is rewarded, so habit is unlikely to explain most human addictive behaviour where these conditions apply. Furthermore, most human studies have not found greater propensity to habitual behaviour in drug users or as a function of dependence severity, and the minority that have can be explained by task disengagement producing impaired explicit contingency knowledge. Compulsion theory of addiction also has weak support. The persistence of punished drug seeking in animals is better explained by greater drug value (evinced by the association with economic demand) than by insensitivity to costs. Furthermore, human studies have provided weak evidence that propensity to discount cost imposed on drug seeking is associated with dependence severity. These data suggest that human addiction is primarily driven by excessive goal-directed drug choice under negative affect, and less by habit or compulsion. Addiction is pathological because negative states powerfully increase expected drug value acutely outweighing abstinence goals.

A concurrent pictorial drug choice task marks multiple risk factors in treatment-engaged smokers and drinkers

Concurrent choice tasks, where participants choose between a drug versus natural reward, predict dependence vulnerability in animals and humans. However, the sensitivity of concurrent choice tasks to multiple risk factors in treatment-engaged drug users has not been comprehensively tested. In experiment 1, 33 recently hospitalized smokers who were engaged with the smoking cessation service made forced choices between enlarging pictures of people smoking versus not smoking. In experiment 2, 48 drinkers who were engaged in an outpatient alcohol treatment service made forced choices between enlarging pictures of alcohol versus food. In these experiments, percent drug picture choice was significantly associated with dependence severity, craving, self-reported reasons for drug use (negative coping and cued craving), depression, anxiety, withdrawal intolerance, drug use frequency prior to treatment, and current abstinence status (coefficients ranged from r=0.39 to 0.66). The concurrent pictorial drug choice task is sensitive to multiple risk factors in clinical, treatment-engaged drug users, and may be used to identify individuals requiring more support, to test experimental treatment manipulations, and to translate to animal concurrent self-administration procedures.

Alcohol use disorder symptoms are associated with greater relative value ascribed to alcohol, but not greater discounting of costs imposed on alcohol

RATIONALE

Alcohol dependence is characterised by persistent drinking despite health, social and economic costs. Behavioural economics has proposed two explanations for the persistence of alcohol use despite costs. Dependent individuals may (a) ascribe excessively high value to alcohol, such that costs associated with alcohol are exceeded, and/or (b) they may discount (neglect) the costs associated with alcohol.

METHODS

To test these predictions, the current study recruited 127 student drinkers who reported varied alcohol use disorder symptom severity in the Alcohol Use Disorders Inventory Test (AUDIT; mean = 11.17, 69% above the hazardous cutoff). Participants made concurrent forced choices between alcohol and food points under conditions that manipulated the magnitude of points (1, 2 or 3) and the delay to receive points (0 or 3 s). Alcohol value was indexed by preferential choice of alcohol versus food points, whereas sensitivity to costs was indexed by the decrease in alcohol choice when food points were of greater magnitude (sensitivity to opportunity costs) and when alcohol points were delayed (sensitivity to delay costs).

RESULTS

Percent choice of alcohol over food varied consistently with the relative magnitude of reward points offered (p < .001) and with time delays imposed on reward points (p < .001). AUDIT scores were associated with greater alcohol versus food choice across all conditions (p = .001). As alcohol use disorder symptom severity increased, the sensitivity of alcohol choice to the relative magnitude of points (p = .29) and time delays (p = .62) remained unchanged, suggesting no differential discounting of opportunity or delay costs imposed on alcohol. In contrasts of AUDIT categories, there was comparable sensitivity to costs across groups defined as low-risk (N = 39), hazardous (n = 57), harmful (n = 20) and possible dependent drinkers (n = 11).

CONCLUSIONS

Alcohol use disorder symptom severity is associated with greater relative value ascribed to alcohol, but not with greater discounting of opportunity or delay costs imposed on alcohol. Despite limitations of the current study, it may be concluded that cost discounting plays a lesser role in dependence than previously thought.

Influence of Cocaine-Related Images and Alcohol Administration on Inhibitory Control in Cocaine Users

BACKGROUND

Alcohol use and impulsivity, including decreased inhibitory control, predict poor treatment outcomes for individuals with cocaine use disorders. This study sought to determine the effects of alcohol administration on inhibitory control following cocaine-related and neutral cues on the Attentional Bias-Behavioral Activation (ABBA) task in cocaine users. We hypothesized that the proportion of inhibitory failures would increase following cocaine, compared to neutral, cues. We further hypothesized that there would be an interaction between alcohol administration and task version, such that alcohol would impair inhibitory control following cocaine, but not neutral cues.

METHODS

Fifty current cocaine users completed this mixed-model, double-blind, placebo-controlled, crossover study over 2 experimental sessions. The ABBA task was completed following alcohol administration (0.0 and 0.65 g/kg). Subject-rated drug effect and physiological measures were collected prior to and after alcohol administration.

RESULTS

Proportion of inhibitory failures was increased following cocaine-related cues compared to neutral cues independent of alcohol dose. Alcohol administration also produced prototypical subject-rated drug effects.

CONCLUSIONS

A better understanding of the relationship between alcohol consumption and inhibitory control in cocaine users could direct the development of interventions to decrease the risk of relapse in individuals who drink and display impaired inhibitory control.

Effects of ethanol on cocaine self-administration in monkeys responding under a second-order schedule of reinforcement

BACKGROUND

Concurrent alcohol use among cocaine abusers is common but the behavioral variables that promote co-abuse are not well understood. The present study examined the effects of intragastric (i.g.) ethanol (EtOH) administration in monkeys responding under a schedule of cocaine reinforcement in which extensive drug seeking was maintained by conditioned stimuli.

METHODS

Four adult male cynomolgus monkeys (Macaca fascicularis) were trained to respond under a second-order fixed-interval (FI) 600s (fixed-ratio (FR) 30:S) schedule of cocaine (0.003-0.56mg/kg/injection) presentation. Sessions ended after 5 injections or 90min had elapsed. Different EtOH doses (0.5-2.0g/kg, i.g.) were administered 30min before the session, typically on Tuesdays and Fridays. Blood ethanol concentrations (BECs) were also assessed. Pattern of FI responding was assessed by determining quarter-life (QL) values.

RESULTS

Cocaine self-administration was characterized as an inverted U-shaped function of dose; QL values increased monotonically with dose. EtOH pretreatments dose-dependently decreased self-administration at several cocaine doses in 3 of 4 monkeys. In one animal, EtOH increased low-dose cocaine-maintained responding. For all monkeys, QL values were increased by EtOH when low- and high-cocaine doses were self-administered, suggesting additive effects of EtOH and cocaine. Furthermore, BECs were not altered following cocaine self-administration.

CONCLUSIONS

The reductions in cocaine self-administration and the increases in QL values following EtOH, suggest that EtOH was enhancing cocaine-related conditioned reinforcement. A better understanding of the behavioral mechanisms that mediate the co-abuse of alcohol and cocaine will lead to improved treatments for both drugs.

Lack of effect of ethanol on cocaine prime-induced reinstatement of extinguished cocaine self-administration in rhesus monkeys

Cocaine and alcohol are commonly co-abused for reasons that are incompletely understood. Laboratory animal studies have suggested that, although the reinforcing effects of low cocaine doses are increased following chronic ethanol (EtOH) consumption, acute EtOH administration does not consistently alter cocaine self-administration. The present study examined whether EtOH influences another abuse-related effect of cocaine: reinstatement of extinguished responding. Rhesus monkeys that had previously consumed EtOH for 8 weeks (2.0 g/kg over 1 h, 5 days/week) self-administered up to 10 injections per day of 0.1 mg/kg cocaine under a fixed-interval 300-s schedule. After responding had been extinguished by substituting saline for cocaine, a pre-session infusion of saline or EtOH (0.5 or 1.0 g/kg, intravenously over 10 min) was followed by a 'priming' injection of saline or cocaine (intravenously). Responding was increased significantly by priming injections of cocaine, but not saline. EtOH infusions neither reinstated behavior when administered before a saline prime nor altered the priming effect of cocaine. The inability of EtOH to alter the response-reinstating ability of cocaine provides further evidence for a lack of acute behavioral interactions between cocaine and EtOH.

Alcohol Administration Increases Cocaine Craving But Not Cocaine Cue Attentional Bias

BACKGROUND

Alcohol consumption is a known antecedent to cocaine relapse. Through associative conditioning, it is hypothesized that alcohol increases incentive motivation for cocaine and thus the salience of cocaine-related cues, which are important in maintaining drug-taking behavior. Cocaine-using individuals display a robust cocaine cue attentional bias as measured by fixation time during the visual probe task. The purpose of this study was to evaluate the influence of alcohol administration on cocaine cue attentional bias using eye-tracking technology to directly measure attentional allocation.

METHODS

Twenty current cocaine users completed a double-blind, placebo-controlled, within-subjects study that tested the effect of 3 doses of alcohol (0.00, 0.325, and 0.65 g/kg) on cocaine cue attentional bias using the visual probe task with eye-tracking technology. The participant-rated and physiological effects of alcohol were also assessed.

RESULTS

Participants displayed a robust cocaine cue attentional bias following both placebo and alcohol administration as measured by fixation time, but not response time. Alcohol administration did not influence cocaine cue attentional bias, but increased craving for cocaine in a dose-dependent manner. Alcohol produced prototypic psychomotor and participant-rated effects.

CONCLUSIONS

Alcohol administration increases cocaine craving but not cocaine cue attentional bias. Alcohol-induced cocaine craving suggests that alcohol increases incentive motivation for cocaine but not the salience of cocaine-related cues.

Cocaine can generate a stronger conditioned reinforcer than food despite being a weaker primary reinforcer

The present study aimed to test the hypothesis that cues associated with drug-taking behavior become extra strong motivators of behavior compared with cues paired with non-drug reinforcers. In experiment 1, rats were trained to lever press for intravenous cocaine infusions and grain pellets. Each reinforcer was paired with a distinct audiovisual cue. When allowed to choose between these alternatives, rats chose grain on ~70-80 percent of trials. However, after extinguishing lever pressing, reintroduction of press-contingent cues during a test for cue-induced reinstatement generated more cocaine seeking than grain seeking (also observed on 3- and 8-week follow-up tests). To examine whether the same pattern of results would occur with two non-drug reinforcers, experiment 2 replicated experiment 1 using grain and sucrose as reinforcement alternatives. Rats chose sucrose over grain on ~70-80 percent of choice trials and also responded more for the sucrose cue than for the grain cue on the reinstatement test. The disconnect between primary and conditioned reinforcements in experiment 1 but not in experiment 2 suggests that drug cues may become exceptionally strong motivators of drug seeking. These results are consistent with cue-focused theories of addiction and may offer insight into the persistent cue-driven drug-seeking behavior observed in addiction.

Cocaine choice procedures in animals, humans, and treatment-seekers: Can we bridge the divide?

Individuals with cocaine use disorder chronically self-administer cocaine to the detriment of other rewarding activities, a phenomenon best modeled in laboratory drug-choice procedures. These procedures can evaluate the reinforcing effects of drugs versus comparably valuable alternatives under multiple behavioral arrangements and schedules of reinforcement. However, assessing drug-choice in treatment-seeking or abstaining humans poses unique challenges: for ethical reasons, these populations typically cannot receive active drugs during research studies. Researchers have thus needed to rely on alternative approaches that approximate drug-choice behavior or assess more general forms of decision-making, but whether these alternatives have relevance to real-world drug-taking that can inform clinical trials is not well-understood. In this mini-review, we (A) summarize several important modulatory variables that influence cocaine choice in nonhuman animals and non-treatment seeking humans; (B) discuss some of the ethical considerations that could arise if treatment-seekers are enrolled in drug-choice studies; (C) consider the efficacy of alternative procedures, including non-drug-related decision-making and 'simulated' drug-choice (a choice is made, but no drug is administered) to approximate drug choice; and (D) suggest opportunities for new translational work to bridge the current divide between preclinical and clinical research.

Effects of chronic binge-like ethanol consumption on cocaine self-administration in rhesus monkeys

BACKGROUND

Most cocaine abusers also abuse alcohol, but little is known about interactions that promote co-abuse. These experiments in rhesus monkeys determined the effects of >8 weeks of ethanol (EtOH) consumption on cocaine self-administration (n=6), effects of dopamine (DA) receptor antagonists on cocaine reinforcement (n=3-4 per drug) and the ability of the D2-like DA receptor agonist quinpirole to elicit yawning (n=3).

METHODS

Monkeys self-administered cocaine (0.0-1.0mg/kg/injection, i.v.) under a 300-s fixed-interval schedule and the above-listed variables were measured before EtOH exposure. Next, monkeys consumed a sweetened, 4% EtOH solution in the home cage under binge-like conditions: 1h, 5 days/week with daily intake equaling 2.0g/kg EtOH. After approximately 8 weeks, measures were re-determined, then EtOH drinking was discontinued. Finally, acute effects of EtOH on cocaine self-administration were determined by infusing EtOH (0.0-1.0g/kg. i.v.) prior to cocaine self-administration sessions (n=4).

RESULTS

In five of six monkeys, EtOH drinking increased self-administration of low cocaine doses but did not alter reinforcing effects of higher doses. Self-administration returned to baseline after EtOH access was terminated (n=3). Effects of DA receptor antagonists on cocaine self-administration were not consistently altered after EtOH consumption, but the ability of quinpirole to induce yawning was enhanced in two of three monkeys. Acute EtOH infusions only decreased self-administration of lower cocaine doses.

CONCLUSIONS

Taken together, the data suggest that long-term EtOH exposure can increase sensitivity to cocaine, possibly by increasing D3 receptor sensitivity. Data do not support a role for acute pharmacological interactions in promoting cocaine/EtOH co-abuse.

Effects of the combination of wheel running and atomoxetine on cue- and cocaine-primed reinstatement in rats selected for high or low impulsivity

BACKGROUND

Aerobic exercise and the attention-deficit/hyperactivity disorder medication, atomoxetine (ATO), are two monotherapies that have been shown to suppress reinstatement of cocaine-seeking in an animal model of relapse. The present study investigated the effects of combining wheel running and ATO versus each treatment alone on cocaine-seeking precipitated by cocaine and cocaine-paired cues in rats with differing susceptibility to drug abuse (i.e., high vs. low impulsive).

METHODS

Rats were screened for high (HiI) or low impulsivity (LoI) based on their performance on a delay-discounting task and then trained to self-administer cocaine (0.4 mg/kg/inf) for 10 days. Following 14 days of extinction, both groups were tested for reinstatement of cocaine-seeking precipitated by cocaine or cocaine-paired cues in the presence of concurrent running wheel access (W), pretreatment with ATO, or both (W+ATO).

RESULTS

HiI rats acquired cocaine self-administration more quickly than LoI rats. While both individual treatments and W+ATO significantly attenuated cue-induced cocaine seeking in HiI and LoI rats, only W+ATO was effective in reducing cocaine-induced reinstatement compared with vehicle treatment. There were dose-dependent and phenotype-specific effects of ATO with HiI rats responsive to the low but not high ATO dose. Floor effects of ATO and W on cue-induced reinstatement prevented the assessment of combined treatment effects.

CONCLUSIONS

These findings demonstrated greater attenuation of cue- versus cocaine-induced reinstatement by ATO and W alone and recapitulate impulsivity phenotype differences in both acquisition of cocaine self-administration and receptivity to treatment.

Reinstatement in a cocaine versus food choice situation: reversal of preference between drug and non-drug rewards

Recent studies show that when given a mutually exclusive choice between cocaine and food, rats almost exclusively choose food. The present experiment investigated potential shifts in preference between levers associated with either food or cocaine that might occur during extinction (food and cocaine no longer available) and during footshock-induced, cocaine-primed and food-primed reinstatement. During self-administration sessions where food and cocaine were simultaneously available, rats demonstrated a stable food preference, choosing food over cocaine on 83% of trials. During extinction when neither reinforcer was available, no preference between levers was evident and responding decreased until rats responded on the previously food- and cocaine-associated levers at equally low rates. Footshock resulted in a non-specific reinstatement of responding upon both levers, while cocaine priming resulted in a significant preference for cocaine seeking over food seeking. This suggests that the mechanism underlying footshock-induced reinstatement is distinct from that of cocaine-primed reinstatement. Food priming engendered a mild, non-specific increase in responding on both levers. Although rats generally prefer food over cocaine when presented with a choice between these primary reinforcers, the present results suggest that in certain situations, cocaine-seeking behavior prevails over food-seeking behavior.

The impact of disulfiram treatment on the reinforcing effects of cocaine: a randomized clinical trial

Background

Clinical trials indicate that disulfiram (250 mg/d) reduces cocaine use, though one study found that treatment with lower doses of disulfiram (62.5 and 125 mg/d) increased cocaine use. We conducted the present study to better understand how disulfiram alters the reinforcing effects of cocaine in cocaine users.

Methods

Seventeen non-treatment seeking, cocaine-dependent volunteers participated in this double-blind, placebo-controlled, laboratory-based study. A cross-over design was utilized in which participants received placebo in one phase and disulfiram (250 mg/d) in the other. Following three days of study medication participants completed two choice sessions. In one they made 10 choices between receiving an intravenous infusion of saline or money that increased in value (US$ 0.05–16) and in the other cocaine (20 mg) or money.

Results

Participants chose cocaine more than saline under both disulfiram and placebo conditions (p<0.05). Unexpectedly, disulfiram increased both the number of cocaine and saline infusion choices (p<0.05). We next examined the relationship between disulfiram dose and cocaine choices. Disulfiram dose (mg/kg bodyweight) was negatively correlated with number of choices for cocaine (p<0.05). Disulfiram also enhanced cocaine-induced increases in cardiovascular measures (p's<0.05–0.01).

Conclusions

Disulfiram's impact on the reinforcing effects of cocaine depends on dose relative to body weight. Our results suggest that the use of weight-based medication doses would produce more reliable effects, consistent with weight-based dosing used in pediatrics and in preclinical research.

Trial Registration

Clinicaltrials.gov NCT00729300

Efficacy of disulfiram and Twelve Step Facilitation in cocaine-dependent individuals maintained on methadone: a randomized placebo-controlled trial

BACKGROUND

Cocaine use remains a major problem within methadone maintenance programs. Disulfiram's efficacy in reducing cocaine use has been demonstrated in several trials, but its relative efficacy among individuals who use versus abstain from alcohol remains unclear. Treatment approaches which seek to enhance substance users' involvement in self-help activities (Twelve Step Facilitation, TSF) have been associated with better outcomes among alcohol and cocaine users, but have rarely been evaluated among methadone-maintained cocaine-opioid users.

METHODS

We conducted a randomized, placebo-controlled, double blind (for medication condition), factorial (2×2) trial with 4 treatment conditions: Disulfiram plus TSF, disulfiram plus standard counseling only, placebo plus TSF, and placebo plus standard counseling in the context of a community-based methadone maintenance program. Participants (N=112) received either disulfiram (250 mg/d) or placebo in conjunction with daily methadone maintenance.

RESULTS

Assignment to TSF was associated with less cocaine use throughout treatment and a higher number of cocaine-negative urines. While there were no significant main effects of disulfiram versus placebo, individuals without an alcohol use disorder demonstrated greater reductions in cocaine use over time when assigned to disulfiram.

CONCLUSIONS

TSF appears feasible in this methadone maintenance program and was associated with modest reductions in cocaine use, an often intractable problem in this setting. Support for the efficacy of disulfiram was weaker, as it appeared effective only for those without a current alcohol use disorder for this sample.

Preference for gamma-hydroxybutyrate (GHB) in current users

Gamma-hydroxybutyrate (GHB) is a drug with significant abuse potential. The present study aimed to assess the relative value of escalating doses of GHB to current GHB users via the Multiple Choice Procedure (MCP), and to validate that the dose rated highest with the MCP would be self-administered at a greater rate than placebo. Participants were 5 current GHB users who were not currently trying to stop using GHB. To examine the value of escalating doses of GHB, the following doses of GHB were used: 0 (placebo), 12.5, 25, 37.5, and 50 mg/kg. Participants typically assigned higher doses of GHB had higher crossover points on the MCP. During choice sessions, participants made repeated choices between administering GHB, placebo or nothing. All participants selected GHB exclusively (5 out of 5 instances) except for one participant who selected GHB on 4 out of 5 instances, thus 96% (i.e., 24/25) of choices were for active GHB. Based on these data, GHB appears likely to function as a dose-dependent reinforcer for humans based on our sample.

Concurrent alcohol dependence among methadone-maintained cocaine abusers is associated with greater abstinence

Concurrent alcohol dependence (AD) among polysubstance abusers has been associated with negative consequences, although it may not necessarily lead to poor treatment outcomes. One of the most efficacious treatments for cocaine abuse is contingency management (CM), but little research has explored the impact of AD on abstinence outcomes, particularly among patients in methadone maintenance. Using data from three trials of CM for cocaine use, we compared baseline characteristics and posttreatment and follow-up cocaine outcomes between methadone-maintained, cocaine-dependent patients (N = 193) with and without concurrent AD, randomized to standard care (SC) with or without CM. Patients with and without concurrent AD had similar baseline characteristics, with the exception that AD patients reported more alcohol use. AD patients achieved longer durations of cocaine abstinence and were more likely to submit a cocaine-negative sample at follow-up than non-AD patients. Patients randomized to CM achieved better outcomes than those randomized to SC, but there was no interaction between treatment condition and AD status. These findings suggest that cocaine-using methadone patients with AD achieve greater cocaine abstinence than their non-AD counterparts and should not necessarily be viewed as more difficult to treat.

Randomized, double blind, placebo-controlled trial of disulfiram for the treatment of cocaine dependence in methadone-stabilized patients

This study examined the dose-related efficacy of disulfiram for treating cocaine dependence in methadone-stabilized cocaine dependent participants.

DESIGN

One hundred and sixty-one cocaine- and opioid-dependent volunteers were entered into a 14-week, double blind, randomized, placebo-controlled clinical trial at two sites.

METHODS

Participants were stabilized on methadone during weeks 1-2 and received disulfiram at 0, 62.5, 125 or 250 mg/day during weeks 3-14. All participants also received weekly cognitive behavioral therapy. Thrice-weekly urine samples and weekly self-reported drug use assessments were obtained.

RESULTS

Baseline subject characteristics, retention and drug use did not differ across groups. Outcome analyses were performed on those who participated beyond week 2. Opioid-positive urine samples and self-reported opioid use did not differ by treatment group. The prevalence of alcohol use was low prior to and during the trial and did not differ by treatment group. Cocaine-positive urines increased over time in the 62.5 and 125 mg disulfiram groups and decreased over time in the 250 mg disulfiram and placebo groups (p < 0.0001). Self-reported cocaine use increased in the 125 mg disulfiram group relative to the other three treatment groups (p = 0.04).

CONCLUSIONS

Disulfiram may be contraindicated for cocaine dependence at doses <250 mg/day. Whether disulfiram at higher doses is efficacious in reducing cocaine use in dually cocaine and opioid dependent individuals needs to be determined.

Monetary alternative reinforcers more effectively decrease intranasal cocaine choice than food alternative reinforcers

Cocaine dependence continues to be a significant public health concern. Contingency management, wherein alternative reinforcers are made available upon cocaine abstinence, has shown promise for decreasing cocaine use. Other research has modeled this effect and demonstrated that alternative reinforcers also reduce cocaine self-administration in the laboratory. Results from both clinical and laboratory studies suggest that the type and value of alternative reinforcers influences their ability to decrease drug choice. The purpose of the present experiment was to determine the effect of money or food alternative reinforcers, valued at $0.01, 0.25, 0.50 and 1.00, on intranasal cocaine (4 [placebo] and 30 mg) choice. Cocaine was chosen to a greater extent than placebo across alternative reinforcer types and values, but the monetary alternative reinforcer suppressed drug choice to a greater degree than the food reinforcer. These results are concordant with previous findings and suggest that money may be a more effective alternative reinforcer for decreasing cocaine use. Future research should determine the sensitivity of this model to specific behavioral aspects of contingency management and whether food could compete with drugs as reinforcers in humans under laboratory conditions.

Abstinence-contingent reinforcement and engagement in non-drug-related activities among illicit drug abusers

Methadone-maintained cocaine abusers (N = 78) were randomly assigned to 1 of the following 52-week interventions: (a) usual care only (UC), (b) take-home methadone doses contingent on cocaine- and opiate-negative results (THM), or (c) take-home methadone doses for cocaine- and opiate-negative results and monetary-based vouchers contingent on cocaine-negative urinalysis results (THM + V). Cocaine use was assessed by urinalysis on a thrice-weekly schedule. Frequency and enjoyability of non-drug-related activities were assessed with the Pleasant Events Schedule (PES) at baseline, midtreatment, and end of treatment. The THM + V condition achieved the greatest abstinence from cocaine and opiate use, followed by the THM and UC conditions. The THM + V condition had the highest PES frequency ratings at midtreatment and at the end of treatment, followed by the THM and UC conditions. There were significant differences between the THM + V and UC conditions on 10 of 12 PES-derived subscales. Analyses revealed that abstinence mediated the effects of treatment condition on frequency ratings. There were no significant differences in enjoyability ratings. These results suggest that when contingency-management interventions increase abstinence from drug abuse, they also increase engagement in non-drug-related activities in naturalistic settings.

Facilitating the adoption of contingency management for the treatment of substance use disorders

Contingency management (CM) is an effective treatment strategy for addressing many types of substance abuse disorders and associated problems. Nonetheless, CM protocols have not been widely embraced by community-based treatment providers. Exploration of the viability of CM outside of a research context remains largely an academic pursuit. In this paper, we outline several areas that may hinder the transfer of CM technology into community-based practice settings, review the literature that may address these barriers, and offer suggestions to researchers for overcoming them.

Medications development: Successes and challenges

The National Institute on Drug Abuse has funded a medications program that has concentrated on the development of medications for opiate and cocaine dependence. Levomethadyl acetate (LAAM) and buprenorphine and buprenorphine/naloxone sublingual tablets were developed in conjunction with pharmaceutical partners and approved by the Food and Drug Administration. The remaining challenges for medications development for opiate dependence involves Phase IV studies in special populations, for example, pregnant opiate-dependent patients, and to translate neuroscience-based findings into treatments. Several marketed medications have shown initial efficacy to reduce cocaine use in well-controlled clinical trials. Disulfiram has been shown to reduce cocaine use in several clinical trials, while baclofen, modafinil, naltrexone, ondansetron, tiagabine, and topiramate have shown preliminary efficacy in initial clinical studies. Confirmatory studies of many of these medications is underway. More recently, the NIDA medications program has evaluated medications for their ability to reduce methamphetamine use. To date, no medications tested have shown efficacy to reduce methamphetamine use. Both marketed medications and investigational agents will be tested. Finally, NIDA has begun to test medications for efficacy to reduce cannabis use. Initial studies are underway. Both agonist and antagonist approaches will be evaluated. Additionally, medications will be tested in cannabis-dependent patients for the management of insomnia, withdrawal, and concurrent depression.

Influence of the duration of abstinence on the relative reinforcing effects of cigarette smoking

RATIONALE

Sustaining smoking abstinence during the initial weeks of a cessation effort is highly correlated with long-term smoking abstinence. However, experimental research is needed to establish a direct causal relationship between achieving early abstinence and lowered relapse risk.

OBJECTIVE

In the present study, we tested whether a period of sustained abstinence directly decreases the relative reinforcing effects of cigarette smoking.

METHODS

Participants were 63 adult smokers who were randomized into one of three conditions: 14-day (14C), 7-day (7C), and 1-day (1C) contingent payment for smoking abstinence. Smoking status was assessed three times per day for 14 consecutive days using breath carbon monoxide monitoring and an abstinence criterion of < or = 4 ppm. In the 14C condition, monetary payment was contingent on abstinence for all 14 days; in the 7C condition, payment was noncontingent for days 1-7 and contingent for days 8-14; in the 1C condition, payment was noncontingent for days 1-13 and contingent for day 14. On day 14, all participants completed a 3-h preference session under controlled laboratory conditions wherein they could make a maximum of 20 exclusive choices between options to smoke (two puffs/choice) or earn money (0.25 dollars/choice). Preference was deemed an index of the relative reinforcing effects of smoking and money.

RESULTS

A significantly lower proportion of participants in the 14C condition ever chose the smoking option (19%) compared to those in the 7C (57%) or 1C (62%) conditions.

CONCLUSIONS

These results provide experimental evidence that sustained abstinence can decrease the relative reinforcing effects of smoking, an effect that may be related to the commonly observed decrease in relapse risk among those who are able to sustain smoking abstinence during the initial weeks of a cessation effort.

Pharmacotherapy and other treatments for cocaine abuse and dependence

PURPOSE OF REVIEW

This review examines progress being made in the treatment of cocaine abuse and dependence, with a particular focus on pharmacotherapies. Medications with apparently very different mechanisms of action have been reported to reduce cocaine use in controlled clinical trials in outpatient settings. This review will summarize the latest findings in this area.

RECENT FINDINGS

Of all the medications tested to date, disulfiram has demonstrated the most consistent effect to reduce cocaine use. Several medications have been reported to reduce cocaine use in double-blind, placebo-controlled clinical trials, namely baclofen, modafinil, tiagabine, and topiramate. All pharmacotherapy trials in cocaine-dependent patients include a behavioral therapy that is common to all participants. Consequently, these pharmacotherapy trials can be considered to evaluate whether the medication is adding to the effect of the behavioral therapy.

SUMMARY

Confirmatory clinical studies are necessary to replicate the initial efficacy findings for baclofen, modafinil, tiagabine, and topiramate. More research is needed in both cocaine and cocaine-alcohol dependent populations. Once confirmatory studies have been carried out, testing of rational medication combinations with different behavioral therapies is an obvious next step to increase the ability to manage cocaine dependence.

A behavioural economic analysis of alcohol, amphetamine, cocaine and ecstasy purchases by polysubstance misusers

Behavioural economic models of substance choice describe the relationship between changes in unit price and consumption. As the majority of UK non-dependent substance misusers are polysubstance misusers, we investigated the influence of price upon hypothetical purchases of alcohol, amphetamine, cocaine and ecstasy. Forty-three current polysubstance misusers (25 males, 18 females; mean age 21.3 +/- 2.8) were recruited into the study. As the price of alcohol rose, demand was inelastic. Amphetamine was a substitute for alcohol, cocaine was a compliment drug and ecstasy was independent. Demand for amphetamine was elastic as its price rose, but only alcohol was identified as a substitute drug and other drug purchases were independent of amphetamine price. As the price of cocaine increased, demand was elastic. Alcohol and ecstasy were substitute drugs but amphetamine purchase was independent, indicating asymmetrical substitution of alcohol and cocaine. Finally, demand for ecstasy was also elastic, but only cocaine substituted as ecstasy price rose. These results extend previous findings in substance dependent populations using behavioural economic models and support the opinion that purchasing substances is a complex process, involving both socio-economic and psychopharmacological factors. Whilst subjects expressed a preference for ecstasy, these behavioural findings indicated that alcohol was their drug of choice when economic considerations were brought into play. Self-reported drug preference, although facilitating between subjects experimental design, may therefore not accurately represent real world polysubstance misuse.

Cocaine, but not alcohol, reinstates cocaine-induced place preferences

Alcohol has been reported to modulate the reinforcing and aversive properties of cocaine. Given these effects, the present study examined whether this interaction could be extended to cocaine seeking using the conditioned place preference (CPP) procedure. Specifically, 31 drug-naive, male Sprague-Dawley rats were injected every other day (for 8 days) with either 20 mg/kg cocaine or vehicle in an alternating sequence prior to being restricted to a drug or vehicle side of a place preference chamber for 30 min. On Day 9, subjects were given 15-min access to the entire chamber to assess compartment preference. Animals then underwent extinction by pairing both compartments with vehicle for an additional 8 days. Extinction was assessed in the same manner as place conditioning. The animals were then given priming injections of vehicle, 15 mg/kg cocaine, 0.5 or 1.0 g/kg alcohol on the day following the extinction test. Pairing 20 mg/kg cocaine with a specific compartment resulted in a significant place preference. Breaking the relation between the compartment and the drug by pairing both compartments with vehicle extinguished this preference. Interestingly, only 15 mg/kg cocaine was able to reinstate the cocaine-induced place preference, suggesting that the ability to reinstate cocaine seeking may be drug specific.

Efficacy of disulfiram and cognitive behavior therapy in cocaine-dependent outpatients: a randomized placebo-controlled trial

CONTEXT

Disulfiram has emerged as a promising treatment for cocaine dependence, but it has not yet been evaluated in general populations of cocaine users.

OBJECTIVES

To compare the effectiveness of disulfiram therapy with that of a placebo condition in reducing cocaine use and to compare the effectiveness of 2 active behavioral therapies-cognitive behavior therapy (CBT) and interpersonal psychotherapy (IPT)-in reducing cocaine use.

DESIGN

Randomized, placebo-controlled, double-masked (for medication condition), factorial (2 x 2) trial with 4 treatment conditions: disulfiram plus CBT, disulfiram plus IPT, placebo plus CBT, and placebo plus IPT.

SETTING

A community-based outpatient substance abuse treatment program.

PATIENTS

A total of 121 individuals meeting the criteria for current cocaine dependence.

INTERVENTIONS

Patients received either disulfiram (250 mg/d) or placebo in identical capsules. Medication compliance was monitored using a riboflavin marker procedure. Both behavioral therapies (CBT and IPT) were manual guided and were delivered in individual sessions for 12 weeks.

MAIN OUTCOME MEASURES

Random regression analyses of self-reported frequency of cocaine use and results of urine toxicology screens.

RESULTS

Participants assigned to disulfiram reduced their cocaine use significantly more than those assigned to placebo, and those assigned to CBT reduced their cocaine use significantly more than those assigned to IPT (P<.01 for both). Findings were consistent across all study samples (eg, intention to treat, treatment initiators, and treatment completers). Benefits of disulfiram use and CBT were most pronounced for participants who were not alcohol dependent at baseline or who fully abstained from drinking alcohol during treatment. Adverse effects experienced by participants who received disulfiram were mild and were not considerably different from those experienced by participants who received placebo.

CONCLUSIONS

Disulfiram and CBT are effective therapies for general populations of cocaine-dependent individuals. Disulfiram seems to exert a direct effect on cocaine use rather than through reducing concurrent alcohol use.

Clinical Implications of Reinforcement as a Determinant of Substance Use Disorders

Extensive scientific evidence indicates that reinforcement plays an important role in the genesis, maintenance, and recovery from substance use disorders. In this chapter, we review recent clinical research from laboratory, clinic, and naturalistic settings examining the role of reinforcement in substance use disorders. Well-controlled human laboratory studies are reviewed characterizing orderly interactions between the reinforcing effects of drugs and environmental context that have important implications for understanding risk factors for substance use disorders and for the development of efficacious interventions. Recent treatment-outcome studies on voucher-based contingency management and community reinforcement therapy are reviewed demonstrating how reinforcement and related principles can be used to improve outcomes across a wide range of different substance use disorders and populations. Overall, the chapter characterizes a vigorous area of clinical research that has much to contribute to a scientific analysis of substance use disorders.

Behavioral and physiological effects of cocaine in humans following triazolam

RATIONALE

Cocaine abuse represents a significant public health problem. Gamma-aminobutyric acid (GABA) agonists may attenuate the behavioral effects of cocaine and may be effective pharmacotherapies for cocaine abuse and dependence.

OBJECTIVES

The aim of this experiment was to determine the combined effects of oral cocaine (0 and 300 mg) and triazolam (0 and 0.5 mg), a GABA(A) modulator, in 10 individuals with recent histories of cocaine use.

METHODS

Volunteers received each of the four possible drug combinations in mixed order. Drug effects were assessed using a battery of subject-rated drug-effect questionnaires and physiological indices.

RESULTS

Cocaine alone produced prototypical stimulant-like subject-rated drug effects (e.g., increased ratings of High, Like Drug, and Willing to Take Drug Again). Triazolam alone produced sedative-like effects (e.g., increased scores on the Pentobarbital, Chlorpromazine, Alcohol Group [PCAG] scale of the Addiction Research Center Inventory [ARCI]). Triazolam pretreatment did not significantly attenuate the subject-rated effects of cocaine.

CONCLUSIONS

While the results of this study do not support the utility of GABA(A) modulators as pharmacotherapies for cocaine abuse, future research should test other benzodiazepines (e.g., alprazolam) using more sophisticated methods (e.g., dose-response curves for the drugs alone and in combination) and behavioral arrangements (e.g., drug discrimination).

The behavioral economics of cigarette smoking: The concurrent presence of a substitute and an independent reinforcer

The present study examined the consumption of cigarettes and two alternative reinforcers in dependent smokers. Cigarette price (response requirement) increased across sessions while alternatives were available at a fixed price in four phases of availability: (1). cigarettes alone; (2). cigarettes and nicotine gum; (3). cigarettes and money; and (4). cigarettes, nicotine gum, and money. Cigarette consumption decreased with increasing price throughout. In the cigarette and nicotine gum phase, nicotine gum consumption increased with cigarette price, indicating nicotine gum to be a substitute for cigarettes. In the cigarette and money phase, money consumption increased slightly with cigarette price, indicating money to be an independent reinforcer for cigarettes. When all three reinforcers were present, money again served as an independent reinforcer. During this phase, nicotine gum consumption increased marginally, but the small magnitude of increase suggests that nicotine gum functioned as an independent reinforcer rather than a substitute. Cigarette consumption decreased modestly when nicotine gum was available, and to a larger extent when money or both alternatives were available. The results highlight the potential for an independent reinforcer such as money to be more effective at reducing drug use than a pharmacological substitute.

Effects of concurrent use of alcohol and cocaine

The combination of alcohol and cocaine is popular among drug users, perhaps because of more intense feelings of 'high' beyond that perceived with either drug alone, less intense feelings of alcohol-induced inebriation and tempering of discomfort when coming down from a cocaine 'high'. A review is presented of the medical literature on psychological and somatic effects and consequences of combined use of alcohol and cocaine in man. The search was carried out with Medline, the Science Citation Index/Web of Science and Toxline. Exclusion and inclusion criteria for this search are identified. There is generally no evidence that the combination of the two drugs does more than enhance additively the already strong tendency of each drug to induce a variety of physical and psychological disorders. A few exceptions must be noted. Cocaine consistently antagonizes the learning deficits, psychomotor performance deficits and driving deficits induced by alcohol. The combination of alcohol and cocaine tends to have greater-than-additive effects on heart rate, concomitant with up to 30% increased blood cocaine levels. Both prospective and retrospective data further reveal that co-use leads to the formation of cocaethylene, which may potentiate the cardiotoxic effects of cocaine or alcohol alone. More importantly, retrospective data suggest that the combination can potentiate the tendency towards violent thoughts and threats, which may lead to an increase of violent behaviours.

Treating antisocial behavior: a context for substance abuse prevention

A large body of literature illustrates an association between antisocial behavior and substance abuse. In the present paper, this association is reviewed from a behavioral-economic standpoint. It is suggested that childhood antisocial behavior is a behavioral complement of substance abuse, and that prosocial behavior is a substitute for substance abuse. Based on this formulation, efforts to reduce or prevent antisocial behavior may be conceptualized as prevention programs for substance abuse. Four empirically supported approaches for the treatment of antisocial behavior are reviewed with respect to their promise for preventing and treating substance abuse. Taken together, they suggest that successful interventions for substance abuse may occur at various points over the course of development, beginning in infancy and extending into adolescence.

A behavioral economic analysis of polydrug abuse in alcoholics: asymmetrical substitution of alcohol and cocaine

Economic concepts can be used to assess how drug prices affect consumption patterns. Increases in price for a commodity typically result in reductions in consumption. Demand is considered elastic if decreases in consumption are proportionally greater than increases in price, and inelastic if they are proportionally smaller than rises in price. The price of one commodity can also affect consumption of others. Commodities can function as substitutes, complements or independents, and these concepts refer to increases, decreases, or no change in the consumption of one item as the price of another increases. This study evaluated the effects of drug prices on hypothetical drug-purchasing decisions in 53 alcohol abusers. Experiments 1, 2, and 3 examined how alcohol, cocaine, and Valium prices, respectively, influenced purchases of alcohol, cocaine, Valium, heroin, marijuana and nicotine. As price of alcohol rose in Experiment 1, alcohol purchases decreased and demand for alcohol was inelastic. Cocaine was a complement to alcohol, but other drugs purchases were independent of alcohol prices. In Experiment 2, demand for cocaine was elastic as its price increased. Alcohol was a substitute for cocaine, but other drug purchases did not change significantly. In Experiment 3, demand for Valium was elastic as its price rose, and all other drug purchases were independent of Valium prices. Hypothetical choices were reliable between and within subjects and associated with urinalysis results and lifetime histories of drug abuse. These results suggest that, among alcohol abusers, cocaine is a complement to alcohol, but alcohol is a substitute for cocaine.

Modulating effect of alcohol use on cocaine use

Clinical observations have indicated that alcohol may be employed by cocaine/crack users to attenuate negative effects of cocaine, especially when "coming down" from a cocaine binge. This issue was examined by interviewing 66 dual cocaine/alcohol users, with opiate dependence histories, enrolled in methadone treatment. A path analysis model was specified to test several hypotheses concerning the possible modulating effects of alcohol use on cocaine use. About 60% of the subjects reported often employing alcohol to ameliorate discomfort associated with tapering or ceasing cocaine/crack use. The main findings were: (a) more intense cocaine/crack craving and feeling that cocaine/crack use was out of control both led to increased use of alcohol to come down; (b) the more frequently alcohol was used to come down, the less use of cocaine/crack; and (c) more cocaine/crack use and more use of alcohol to come down both led to increased heavy alcohol use. Thus, treating alcohol abuse in this population must take into account the important function it serves in modulating cocaine/crack use.

Cocaine and alcohol interactions in the rat: effect of cocaine and alcohol pretreatments on cocaine pharmacokinetics and pharmacodynamics

This experiment was designed to investigate the effect of pretreatment with cocaine and alcohol on cocaine pharmacokinetics and pharmacodynamics. Four groups of rats (n = 8 per group) received one of the following pretreatments for two weeks: none, alcohol (10% v/v in drinking water), cocaine (15 mg/kg/day ip), and alcohol+cocaine (10% v/v in drinking water + 15 mg/kg/day ip). On the day of the experiment, cocaine was administered (30 mg/kg, ip) to each rat, either alone or in combination with alcohol (5 g/kg, po), in a balanced crossover experimental design. Plasma and brain ECF concentrations of cocaine and its three metabolites: benzoylecgonine, norcocaine, and cocaethylene were assayed by HPLC-UV. The percent change in brain dopamine concentration, mean arterial blood pressure, and heart rate were determined simultaneously. A sigmoid-E(max) model was used to describe the brain cocaine concentration-neurochemical effect (dopamine) relationship, and an indirect pharmacodynamic response model was used to describe the plasma cocaine concentration-cardiovascular effect relationships. Alcohol pretreatment led to significant increase in cocaine AUC(p), alpha(t1/2), and beta(t1/2). Cocaine pretreatment significantly increased cocaine bioavailability, absorption rate constant, TBC, and the formation clearance of cocaethylene. Acute alcohol coadministration with cocaine increased cocaine AUC(p) and bioavailability, reduced the fraction of cocaine dose converted to benzoylecgonine, and increased the formation of norcocaine. These results indicate that the pharmacokinetics of cocaine, either administered alone or in combination with alcohol, is significantly altered due to prior cocaine and/or alcohol use. Both cocaine and alcohol pretreatments increased the E(max) for dopamine, with no effect on the EC(50). Acute alcohol coadministration with cocaine significantly increased the E(max) for dopamine and reduced the EC(50). Cocaine pretreatment significantly decreased the I(max) for blood pressure, IC(50), and R(max). For the heart rate response, both alcohol and cocaine pretreatments significantly increased the IC(50), with no effect on I(max). These results indicate that both cocaine and alcohol pretreatments as well as acute alcohol coadministration lead to significant alterations in cocaine pharmacodynamics that are due, at least in part, to the changes in cocaine pharmacokinetics. If similar effects occur in humans, chronic cocaine and alcohol abusers may respond differently to cocaine administration compared to naïve users and may be at higher risks of cocaine central nervous system toxicity.

Acute physiological and behavioral effects of oral cocaine in humans: a dose-response analysis

The present study was designed to assess the acute physiological and behavioral effects of a wide range of doses of oral cocaine HCL (placebo, 50, 100, 200, and 300 mg). Nine volunteers (eight males and one female) with recent histories of cocaine use resided on a general inpatient psychiatry unit while they participated. Drug doses were administered in a double-blind fashion under medical supervision, but for safety purposes, they were administered in ascending order. The physiological, subject-rated, and performance effects of oral cocaine HCL were assessed before drug administration and periodically afterwards for 5 h. Oral cocaine HCL increased heart rate and blood pressure as a graded function of dose, but the magnitude of these effects were not clinically significant. Oral cocaine HCL produced positive subject-rated drug effects (e.g. increased ratings of good effects, like drug, and willing to take again), but did not affect performance. Consistent with the pharmacokinetics of oral cocaine HCL, drug effects were generally discernible from placebo 0.5-1 h after administration, peaked approximately 1 h after administration, and progressively abated during the remainder of the experimental session. The results of this experiment demonstrate that across a six-fold range of doses oral cocaine HCL is well tolerated by individuals with recent histories of cocaine use and can be safely administered under controlled laboratory and medical conditions.

Preclinical research on cocaine self-administration: environmental determinants and their interaction with pharmacological treatment

It has been asserted that any comprehensive understanding of cocaine abuse and its treatment will require attention to both behavioral and pharmacological variables. Although the preclinical literature evaluating the effects of pharmacological variables on cocaine self-administration has been extensively reviewed, no comprehensive review of the effects of environmental variables on cocaine self-administration has been published. The present review summarizes and critiques the preclinical findings on environmental determinants of cocaine self-administration. The influence of environmental variables on the effects of pharmacological interventions on cocaine self-administration are also described. Several environmental variables have been shown to affect cocaine self-administration, including unit dose, schedule of cocaine delivery, schedules of nondrug stimuli, behavioral history, conditioned stimuli, food deprivation, exposure to stress, and rearing environment. Among these variables, unit dose, schedule of cocaine delivery, availability of alternative nondrug reinforcers, food deprivation, and rearing environment have also been shown to alter pharmacological treatment effects on cocaine self-administration. Thus, drug effects on cocaine self-administration are malleable and dependent upon the environmental context within which they occur. Suggestions for future research on the effects of these and other environmental variables on cocaine self-administration and its pharmacological treatment are presented.

Cocaine metabolism in humans after use of alcohol. Clinical and research implications

The simultaneous administration of cocaine and alcohol implies a pharmacological interaction at pharmacodynamic and pharmacokinetic levels. The latter involves an alteration of cocaine kinetics and metabolism, as well as the biosynthesis of newly active metabolites, such as cocaethylene. Cocaethylene is metabolized along the same pathways as cocaine. Its detection in biological samples indicates the combined consumption of cocaine and alcohol. From epidemiological and toxicological data, it has been suggested that the combination of alcohol and cocaine produces an increased toxicity in addition to behavioral changes. There has been some debate regarding the contribution of cocaethylene to this rise of toxicity. Its pharmacological and toxicological profile is very similar to cocaine. During the interaction of both substances, the rise in cocaine plasma concentrations can explain many of cardiovascular and behavioral effects observed. The contribution of cocaethylene to the interaction is probably minor; its effects are likely additive to those of cocaine. Perhaps its longer elimination half-life can help in understanding long-lasting effects of the alcohol-cocaine combination.

Disulfiram effects on acute cocaine administration

Disulfiram (Antabuse) is being used in outpatient clinical trials to determine its efficacy as a treatment for cocaine dependence. This inpatient randomized, double-blind, placebo-controlled, within-subjects study was conducted to determine whether disulfiram (placebo, 250 or 500 mg/day) alters responses to acute intranasal cocaine (placebo, 1 or 2 mg/kg) administration. Effects of disulfiram on cocaine pharmacokinetics, physiological, and behavioral responses were determined. Disulfiram treatment increased plasma cocaine concentrations three to six times and significantly increased cocaine-associated cardiovascular responses, but did not significantly alter behavioral responses to cocaine. These interactions should be considered in the decision regarding disulfiram treatment in cocaine dependent patients.

Cocaine and alcohol synergism in taste aversion learning

Female Long-Evans rats were given 20-min access to saccharin followed by injections of alcohol and cocaine, alone and in combination. Although there was no significant interaction between alcohol and cocaine when cocaine was given intraperitoneally (IP), aversions induced by the drug combination when cocaine was administered subcutaneously (SC) were significantly greater than those induced by either drug alone. Further, the aversions induced by the combination were significantly greater than the summed effects of the individual drugs administered alone, indicating a synergistic interaction between cocaine and alcohol. It was suggested that this synergism might result from a summation of the effects of alcohol, cocaine, and cocaethylene, a unique and toxic metabolite of cocaine produced when alcohol is coadministered. To assess the role of cocaethylene in the present design, additional taste aversion assessments were performed in which saccharin was paired with either IP or SC injections of cocaethylene. Although cocaethylene was found to induce aversions, the summed changes in consumption from baseline produced by cocaine, alcohol, and cocaethylene were significantly less than the changes produced by cocaine and alcohol in combination. These results indicate that the synergistic interaction between cocaine and alcohol in the present design cannot be attributed solely to summation of the effects of the individual drugs and the metabolite cocaethylene. Additional mechanisms by which cocaethylene might contribute to the synergistic interaction between cocaine and alcohol, as well as the role pharmacokinetic interactions between cocaine and alcohol might have in the interaction, were discussed.

Treatment outcome of cocaine-alcohol dependent patients

Cocaine dependent patients (n = 27) with and without concurrent alcohol dependence disorder were compared on measures of substance use, addiction severity (ASI), coping, and psychopathology taken before, during, and after outpatient relapse prevention treatment for cocaine dependence. At pre-treatment, the cocaine-alcohol (CA) group reported more frequent alcohol use, and more severe alcohol and family/social problems compared to the cocaine-only (CO) group. By the end of treatment, both groups reported significantly fewer days of alcohol and cocaine use, with sustained reductions observed at 24 weeks following treatment. On most of the addiction severity and psychiatric symptomatology scales, results indicated overall improvement as a function of time, however scores remained relatively 'worse' in the CA group. Implication of these findings and the need for specific programming in the treatment of dual drug use are explored.

The influence of alternative reinforcers on cocaine use and abuse: a brief review

This report reviews experimental studies conducted with nonhuman and human subjects demonstrating that: a) cocaine's abuse liability is, in part, a function of its positive reinforcing effects, b) cocaine use is operant behavior, c) the degree of behavioral control that cocaine exerts as a reinforcer is malleable and dependent on environmental context, and d) increasing the availability of alternative, nondrug reinforcers can significantly disrupt the acquisition and maintenance of cocaine use and abuse. Implications of these observations for effective prevention and treatment of cocaine abuse are discussed.