Neurobiological adaptations to psychostimulants and opiates as a basis of treatment development

A morphine/heroin vaccine with new hapten design attenuates behavioral effects in rats

Heroin use has seriously threatened public heath in many countries, but the existing therapies continue to have many limitations. Recently, immunotherapy has shown efficacy in some clinical studies, including vaccines against nicotine and cocaine, but no opioid vaccines have been introduced in clinical studies. The development of a novel opioid antigen designed specifically for the prevention of heroin addiction is necessary. A morphine-keyhole limpet hemocyanin conjugate was prepared and administered subcutaneously in rats. Antibody titers in plasma were measured using an enzyme-linked immunosorbent assay (ELISA). Competitive ELISA was used to assess the selectivity of the antibodies. Dopamine concentrations in the nucleus accumbens in rats after vaccine administration were determined by high-performance liquid chromatography with electrochemical detection. The effects of the vaccine on the heroin-primed restatement of self-administration and locomotor sensitization were evaluated. A novel hapten, 6-glutarylmorphine, was produced, and the vaccine generated a high antibody titer response. This vaccine displayed specificity for both morphine and heroin, but the anti-morphine antibodies could not recognize dissimilar therapeutic opioid compounds, such as buprenorphine, methadone, naloxone, naltrexone, codeine, and nalorphine. The morphine antibody significantly decreased morphine-induced locomotor activity in rats after immunization. Importantly, rats immunized with this vaccine did not exhibit heroin-primed reinstatement of heroin seeking when antibody levels were sufficiently high. The vaccine reduced dopamine levels in the nucleus accumbens after morphine administration, which is consistent with its behavioral effects. These results suggest that immunization with a novel vaccine is an effective means of inducing a morphine-specific antibody response that is able to attenuate the behavioral and psychoactive effects of heroin.

Pharmacotherapies for problematic psychostimulant use: a review of current research

This review summarizes the current status of clinical research on pharmacotherapies for problematic psychostimulant use. The use of psychostimulants, including amphetamine, cocaine and ecstasy, is increasingly a feature of Australian life as is the presentation of patients with psychostimulant disorders. A lack of experience, resources and treatment options have constrained the response of treatment services to such problems. Despite extensive research, particularly in the area of cocaine, no pharmacotherapy has been proven effective in the management of psychostimulant disorders. The harms associated with problematic psychostimulant use warrant further controlled research in innovative approaches integrated with psychosocial interventions.

Development and evaluation of the heroin abstainers' cue-sensitization questionnaire

In order to develop the heroin abstainers' cue-sensitization questionnaire (HACSQ), and evaluate its reliability and validity, during March and April in 2006, the cross-sectional sample survey and cluster sampling were adopted among 939 volunteer participants who were heroin abstainers from 5 compulsive detoxification centers in China. The data were collected by the self-report questionnaires. The reliability analysis included Cronbach's alpha coefficient, split reliability and test-retest reliability, while construction validity was analyzed in the light of exploratory and confirmatory factor analysis. Based upon the exploratory factor analysis, 4 factors were extracted, which were social emotion cue (SEC), direct implement cue (DIC), personnel cue (PC) and indirect implement cue (IIC), and they together explained 64.52% variance. According to the data, test-retest reliability coefficient ranged from 0.57 to 0.63, and Cronbach's alpha coefficient ranged from 0.86 to 0.95 across the 4 factors and HACSQ. The adjusted goodness of fit index was 0.75. It was suggested that the HACSQ demonstrated good validities and reliabilities, and may be used as a reliable assessment tool for the cue-sensitization among the heroin abstainers.

The principles of agonist pharmacotherapy for psychostimulant dependence

ISSUES

Psychostimulant dependence is a chronic, relapsing condition which is highly treatment refractory. No medications to date have been any more successful than placebo in reducing psychostimulant use in dependent patients. Agonist strategies have attracted limited attention.

APPROACH

Successful examples of agonist pharmacotherapy in the treatment of heroin and nicotine dependence are first considered. Agonist pharmacological approaches to the treatment of psychostimulant dependence are then examined, based on the dopamine receptor agonist and indirect dopamine agonist strategies. Finally, the potential extension of the concept of agonist pharmacotherapy to include the novel non-amphetamine-type stimulant, modafinil, is discussed.

CONCLUSIONS

Agonist approaches appear to be viable with risks outweighed by benefits in carefully selected, monitored and motivated patients. On the other hand, the effectiveness of indirect agonists such as dexamphetamine and methylphenidate are not established. Further research is required to determine optimal treatment models (whether maintenance or withdrawal), effective safe dosages and duration (short or long term).

Antagonist treatment of opioid withdrawal translational low dose approach

Although antagonist drugs are receiving increasing attention in the treatment of opioid withdrawal, the mechanisms of interaction of opiate agonists and antagonists remain largely to be investigated. We focused on the effects of very low quantities of opiate antagonists, following the clinical indication of their potential utility in detoxification. Upon reviewing the evidence on the administration of small doses of naloxone and naltrexone in the presence of agonist drugs, the effects of low-dose naltrexone during opiate administration and withdrawal are described. The application of a translational methodology allowed completing the clinical design with behavioral and cellular information obtained from a specifically developed animal model. The initial results indicate that low doses of naltrexone may help reducing the manifestation of opioid withdrawal, offer suggestions for further investigations and confirm the utility of a translational research approach to the clinical neurobiology of drug addiction.

Topiramate in Opiate Withdrawal-Comparison with Clonidine and with Carbamazepine/Mianserin

There are some rationales for developing anticonvulsants for the treatment of substance abuse. The blockade of the AMPA/kainate subtype of glutamate receptor by topiramate may be of particular interest, as preclinical studies of withdrawal from opioids suggest that whilst AMPA-receptor antagonists may not be able to prevent tolerance or dependence from developing, they may ameliorate both physical and emotional consequences of withdrawal.

METHODS

Ten consecutively admitted patients treated with topiramate were compared in a retrospective naturalistic drug utilization observation study with 10 consecutively admitted patients treated with clonidine and with 10 consecutively admitted patients treated with a carbamazepine/ mianserin combination.

RESULTS

In 9 cases of the clonidine group and in 7 carbamazepine/mianserin treated patients the dose had been reduced, whereas this occurred in only 2 topiramate treated patients (p < 0.01). Patients in the topiramate group received less p.r.n. myorelaxant medication than the two other groups, and there was a significant difference between the three groups with regard to p.r.n. analgesics (p < 0.05), topiramate and clonidine treated patients receiving fewer analgesics than the carbamazepine/mianserin group.

CONCLUSIONS

Compared to clonidine and carbamazepine/mianserin, a detoxification scheme using high initial and then decreasing doses of topiramate appeared to be appropriate for most patients and as associated with less analgesic and myorelaxant comedication, indicating a more promising efficacy at the used doses.

The effect of sertraline and environmental context on treating depression and illicit substance use among methadone maintained opiate dependent patients: a controlled clinical trial

Psychiatric comorbidity, particularly depressive disorders, is associated with continued substance use and poor social functioning among methadone maintained patients. Evidence suggests similar neurochemical and environmental pathways may link the two disorders and it is reasonable to hypothesize that pharmacological and environmental factors play important roles in the treating comorbid depression and substance use. The present study tested the efficacy of sertraline for treating syndromally defined depressive disorders among non-abstinent methadone maintained opiate dependent patients. The moderating effects of environmental context on treatment outcome were also examined. Ninety-five patients were randomized in a 12-week, double-blind, placebo-controlled trial of sertraline, a serotonin-selective re-uptake inhibitor. There was no main effect of sertraline on either depression or substance use outcomes. However, sertraline demonstrated significant ameliorative effects on depression among patients with a more positive environment or less negative environment. The odds of being abstinent from heroin and cocaine were greater for patients on sertraline in environments with relatively less adversity. The findings support the hypothesis that contextual factors moderate the efficacy of pharmacological treatment for depression among methadone patients. They also suggest future research should examine a pharmacological treatment that is combined with a behavioral intervention targeting the accessibility of reinforcement or reducing the impact of aversive environmental interactions.