Choice of blind methadone dose increases by methadone maintenance patients

The behavioral economics of drug dependence: towards the consilience of economics and behavioral neuroscience

In this chapter, we review the research in this growing field by first discussing the concepts related to price and consumption (demand), its applications to the study of drug consumption and drug seeking, and the impact of other commodities on drug consumption. We then review the discounting of future commodities and events among the addicted, review the most recent research examining the neural correlates of discounting, and describe and review the new theory of addiction that results from that research. We conclude by addressing the next research steps that these advances engender.

Morphine actions in the rat forebrain: role of protein kinase C

Acute administration of morphine induces expression of the immediate-early gene (IEG) c-Fos in dorsomedial striatum, portions of cerebral cortex, and in several midline-intralaminar thalamic nuclei, partly via a trans-synaptic mechanism that involves activation of glutamate receptors. Because activation of protein kinase C (PKC) may occur following the activation of glutamate receptors, we determined whether pharmacological inhibition of PKC would attenuate morphine-induced c-Fos expression, and whether acute administration of morphine would induce translocation of PKC. The selective PKC antagonist NPC 15437 given 30 min prior to morphine significantly decreased morphine-induced c-Fos expression in striatum and cingulate cortex, but not in centrolateral thalamus. In another experiment, rats were given an acute dose of morphine, and immunocytochemical analysis was performed for the betaI and betaII isoforms of PKC. Morphine induced a rapid and transient translocation of PKC betaII, but not betaI, from perinuclear spots to plasma membrane in numerous cortical and striatal neurons. Prior administration of naloxone blocked this response. Ultrastructural studies confirmed translocation from Golgi apparatus to plasma membrane 15 min after morphine injection. Double immunocytochemistry at the light microscopic level demonstrated co-localization of translocated PKC betaII and c-Fos in some cortical neurons 90 min after morphine injection. These results support a role for PKC, especially PKC betaII, in the rapid effects of morphine on the brain.

Behavioral economics of concurrent ethanol-sucrose and sucrose reinforcement in the rat: effects of altering variable-ratio requirements

These experiments examined the own-price and cross-price elasticities of a drug (ethanol mixed with 10% sucrose) and a nondrug (10% sucrose) reinforcer. Rats were presented with ethanol-sucrose and sucrose, both available on concurrent independent variable-ratio (VR) 8 schedules of reinforcement. In Experiment 1, the variable ratio for the ethanol mix was systematically raised to 10, 12, 14, 16, 20, and 30, while the variable ratio for sucrose remained at 8. Five of the 6 rats increased ethanol-reinforced responding at some of the increments and defended baseline levels of ethanol intake. However, the rats eventually ceased ethanol-reinforced responding at the highest variable ratios. Sucrose-reinforced responding was not systematically affected by the changes in variable ratio for ethanol mix. In Experiment 2, the variable ratio for sucrose was systematically increased while the ethanol-sucrose response requirement remained constant. The rats decreased sucrose-reinforced responding and increased ethanol-sucrose-reinforced responding, resulting in a two- to 10-fold increase in ethanol intake. Experiment 3 examined the substitutability of qualitatively identical reinforcers: 10% sucrose versus 10% sucrose. Increases in variable-ratio requirements at the preferred lever resulted in a switch in lever preference. Experiment 4 examined whether 10% ethanol mix substituted for 5% ethanol mix, with increasing variable-ratio requirements of the 5% ethanol. All rats eventually responded predominantly for the 10% ethanol mix, but total amount of ethanol consumed per session did not systematically change. In Experiment 5, the variable-ratio requirements for both ethanol and sucrose were simultaneously raised to VR 120; 7 of 8 rats increased ethanol-reinforced responding while decreasing sucrose-reinforced responding. These data suggest that, within this ethanol-induction procedure and within certain parameters, demand for ethanol-sucrose was relatively inelastic, and sucrose consumption was independent of ethanol-sucrose consumption. Demand for sucrose, on the other hand, was relatively elastic, and ethanol-sucrose readily substituted for it. The results are discussed in terms of applying a behavioral economic approach to relationships between drug and nondrug reinforcers.

The behavioral economics of concurrent drug reinforcers: a review and reanalysis of drug self-administration research

In economics, goods can function as substitutes, complements, or be independent of one another. These concepts refer to increases, decreases, or no change in the consumption of one item as the price of a second item increases. This review examined whether these economic terms can be used to describe relationships between concurrently available reinforcers in drug self-administration research. Sixteen drug self-administration studies that examined the effects of concurrent reinforcers were identified through a MEDLINE search. Across these studies, the following substances were employed: caffeinated coffee, cocaine, etonitazene, ethanol, heroin, food, methadone, morphine, nicotine cigarettes, pentobarbital, phencyclidine, sucrose and water. These studies were reanalyzed and the results were shown to be consistent with these economic notions. These analyses also showed that relationships among the concurrently available reinforcers were reliable within and across studies, that concurrently available reinforcers can affect each other asymmetrically, and that the relative price may determine the magnitude of effect for substitutes. These findings suggest that these economic concepts may be useful in characterizing the type and magnitude of interactions between concurrently available reinforcers and may suggest potential mechanisms that determine these relationships.

Preference for high- versus low-potency marijuana

With many drugs of abuse, humans and other species display a preference for higher doses (or more potent dosage forms) over lower doses (or less potent dosage forms). The present study was designed to determine whether this generalization would hold for marijuana smoking by humans. Twelve regular marijuana smokers participated in two independent and identical choice trials in which, on separate sessions, they first sampled marijuana of two different potencies (0.63% and 1.95% delta-9-tetrahydrocannabinol; THC) and then, on the next session, chose which of the two, as well as how much, to smoke. During sampling sessions, the high-potency marijuana produced a greater heart rate increase and greater subjective effects than the low-potency marijuana. Subjects chose the high-potency marijuana significantly more often than the low-potency marijuana (21 out of 24 choice occasions). These results support the hypothesis that the reinforcing effects of marijuana, and possibly its abuse liability, are positively related to THC content.

Abuse liability studies of opioid agonist-antagonists in humans

Prediction of the abuse liability of a drug before it reaches the market is complicated by the fact that there are many factors that influence the actual abuse of a drug. Laboratory methods used in humans to assess the abuse liability of the opioids are reviewed and illustrative studies of morphine and the agonist-antagonist opioids, pentazocine, butorphanol, nalbuphine and buprenorphine, are presented. Three assessment methods, subjective effect measurement, self-administration and drug discrimination, provide information relevant to measuring reinforcing efficacy, a major determinant of the degree to which a drug is sought and self-administered by abusers. Physical dependence capacity, which can contribute to sustained drug use, is evaluated in direct addiction and substitution/suppression studies. Withdrawal precipitation studies measure antagonist activity which might limit abuse. The results of testing the agonist-antagonist opioids are generally consistent across these various methods and consistent with historical experience with these drugs, suggesting that these methods are useful in predicting abuse liability of novel opioids.

Major psychotherapeutic modalities for heroin addiction: a brief overview

This article provides a brief overview of recent literature on major psychotherapeutic modalities for heroin addiction. These modalities include psychotherapy, behavior therapy, cognitive-behavioral therapy, family therapy, social skills training approaches, and therapeutic communities. It highlights studies with stronger research design and methodology, many of which are theory-based, and discusses what appear to be the "active ingredients" in these modalities which contribute to successful treatment outcome. It concludes that there is an increasing convergence of theory and research in the field of heroin addiction treatment, making the designing of treatment programs based on empirical knowledge more feasible.

Contingency management in methadone maintenance: effects of reinforcing and aversive consequences on illicit polydrug use

Treatment outcomes were compared for an intervention emphasizing reinforcement for abstinence from illicit drug use and an alternative intervention which combined the same reinforcement contingencies with aversive consequences for unauthorized drug use. Sixteen polydrug abusing methadone maintenance patients were randomly assigned to one of two treatment groups. Both groups received the opportunity to take methadone doses away from the clinic (take-home dose) as reinforcement for submitting urines testing negative for illicit substances. A regular weekly take-home dose of methadone could be earned for every 2 weeks of verified abstinence from unauthorized drugs, up to a maximum of three take-home doses per week. The combined intervention group had an additional contingency which involved a reduction in methadone dose as an aversive consequence for submitting urine samples testing positive for illicit substances. Specifically, 10% of the patient's daily methadone dose was lost for each week in which two of three urines tested positive for illicit drugs. An examination of the urinalysis results indicated no between group differences. Overall, 8% of the 12-week baseline urinalysis results tested negative for illicit substances while 42% tested negative for unauthorized substances during the 20 weeks of treatment intervention. At the end of the intervention period, nine subjects remained in treatment with three patients in each group receiving at least once weekly take-home privileges. Of the seven subjects no longer in treatment, five were in the combined intervention group.(ABSTRACT TRUNCATED AT 250 WORDS)

Combined behavioral and pharmacological treatment of alcoholic methadone patients

Alcoholism is a prevalent and often debilitating problem among methadone maintenance patients. In this study, the efficacy of a contingency management program in the treatment of three severely alcoholic methadone patients was examined using within-subject experimental designs. The contingency management program made continuation in methadone maintenance contingent upon daily disulfiram consumption. Failure to consume disulfiram resulted in the transfer of the patient to another methadone program. This treatment resulted in clinically significant decreases in alcohol consumption and improvements in clinic attendance.

Effect of methadone dose contingencies on urinalysis test results of polydrug-abusing methadone-maintenance patients

Drug abuse outcomes were examined during 2 contingency management procedures in which the size of the methadone dose was determined by recent urinalysis test results. Twenty polydrug-abusing methadone-maintenance patients were exposed to one of two specific altered dose consequences: a positive incentive procedure in which dose could only increase above baseline levels as a result of drug-free urines and a negative incentive procedure in which dose could only decrease below original baseline levels as a result of drug-positive urines. About 13% of urinalysis test results were drug-free during a 10-week pre-study baseline period while about 40-50% of urines were drug-free for both treatment groups during an 18-week intervention period. About half of the subjects in each study condition showed marked improvement during the intervention, while the other half failed to improve their urine test results. Treatment failures in the dose decrease as compared with the dose increase condition were more likely to drop out of the study. The study showed that size of the methadone dose can be effectively used as a consequence to influence illicit drug use during treatment. The study suggests that positive reinforcement as compared with aversive control procedures can produce an equivalent number of successful cases while avoiding dropout among patients who fail to respond to treatment.