Flupenthixol as a potential pharmacotreatment of alcohol and cocaine abuse/dependence

Increased elasticity of sucrose demand during hyperdopaminergic states in rats

RATIONALE

Deficits in cost-benefit decision-making are a core feature of several psychiatric disorders, including substance addiction, eating disorders and bipolar disorder. Mesocorticolimbic dopamine signalling has been implicated in various processes related to cognition and reward, but its precise role in reward valuation and cost-benefit trade-off decisions remains incompletely understood.

OBJECTIVES

We assessed the role of mesocorticolimbic dopamine signalling in the relationship between price and consumption of sucrose, to better understand its role in cost-benefit decisions.

METHODS

Dopamine neurons in the ventral tegmental area (VTA) were chemogenetically activated in rats, and a behavioural economics approach was used to quantify the relationship between price and consumption of sucrose. Motivation for sucrose was also assessed under a progressive ratio (PR) schedule of reinforcement. To further gauge the role of dopamine in cost-benefit trade-offs for sucrose, the effects of treatment with D-amphetamine and the dopamine receptor antagonist alpha-flupentixol were assessed.

RESULTS

Chemogenetic activation of VTA dopamine neurons increased demand elasticity, while responding for sucrose under a PR schedule of reinforcement was augmented upon stimulation of VTA dopamine neurons. Treatment with amphetamine partially replicated the effects of chemogenetic dopamine neuron activation, whereas treatment with alpha-flupentixol reduced free consumption of sucrose and had mixed effects on demand elasticity.

CONCLUSIONS

Stimulation of mesocorticolimbic dopaminergic neurotransmission altered cost-benefit trade-offs in a complex manner. It reduced the essential value of palatable food, increased incentive motivation and left free consumption unaltered. Together, these findings imply that mesocorticolimbic dopamine signalling differentially influences distinct components of cost expenditure processes aimed at obtaining rewards.

Implication of dopaminergic modulation in operant reward learning and the induction of compulsive-like feeding behavior in Aplysia

Feeding in Aplysia provides an amenable model system for analyzing the neuronal substrates of motivated behavior and its adaptability by associative reward learning and neuromodulation. Among such learning processes, appetitive operant conditioning that leads to a compulsive-like expression of feeding actions is known to be associated with changes in the membrane properties and electrical coupling of essential action-initiating B63 neurons in the buccal central pattern generator (CPG). Moreover, the food-reward signal for this learning is conveyed in the esophageal nerve (En), an input nerve rich in dopamine-containing fibers. Here, to investigate whether dopamine (DA) is involved in this learning-induced plasticity, we used an in vitro analog of operant conditioning in which electrical stimulation of En substituted the contingent reinforcement of biting movements in vivo. Our data indicate that contingent En stimulation does, indeed, replicate the operant learning-induced changes in CPG output and the underlying membrane and synaptic properties of B63. Significantly, moreover, this network and cellular plasticity was blocked when the input nerve was stimulated in the presence of the DA receptor antagonist cis-flupenthixol. These results therefore suggest that En-derived dopaminergic modulation of CPG circuitry contributes to the operant reward-dependent emergence of a compulsive-like expression of Aplysia's feeding behavior.

Therapeutic drug monitoring of common antipsychotics

The aim of this review is to provide information for interpreting outcome results from monitoring of antipsychotics in biological samples. A brief overview of the working mechanisms, pharmacological effects, drug interactions, and analytical methods of classical and atypical antipsychotics is given. Nineteen antipsychotics were selected based on their importance in the worldwide market as follows: amisulpride, aripiprazole, asenapine, bromperidol, clozapine, flupenthixol, haloperidol, iloperidone, lurasidone, olanzapine, paliperidone, perphenazine, pimozide, pipamperone, quetiapine, risperidone, sertindole, sulpiride, and zuclopenthixol. A straightforward relationship between administered dose, plasma or serum concentration, clinical outcome, or adverse effects is often lacking. Nowadays, focus lies on therapeutic drug monitoring and individualized therapy to find adequate treatment, to explain treatment failure or nonresponse, and to check patient compliance. However, extensive research in this field is still mandatory.

Levo-tetrahydropalmatine inhibits cocaine's rewarding effects: experiments with self-administration and brain-stimulation reward in rats

It was recently reported that levo-tetrahydropalmatine (l-THP), a dopamine (DA) D1 and D2 receptor antagonist purified from the Chinese herb Stephanie, appears to be effective in attenuating cocaine self-administration, cocaine-triggered reinstatement and cocaine-induced conditioned place preference in preclinical animal models. The present study was designed to contrast l-THP's effects on cocaine self-administration under fixed-ratio (FR) and progressive-ratio (PR) reinforcement, and to study l-THP's effects on cocaine-enhanced brain stimulation reward (BSR). Systemic administration of l-THP produced dose-dependent, biphasic effects, i.e., low-to-moderate doses (1, 3, 10 mg/kg) increased, while a high dose (20 mg/kg) inhibited cocaine self-administration behavior under FR2 reinforcement. The increased cocaine self-administration is likely a compensatory response to a reduction in cocaine's rewarding effects, because the same low doses of l-THP dose-dependently attenuated cocaine self-administration under PR reinforcement and also attenuated cocaine-enhanced BSR. These attenuations of PR cocaine self-administration and cocaine-enhanced BSR are unlikely due to l-THP-induced sedation or locomotor inhibition, because only 10 mg/kg, but not 1-3 mg/kg, of l-THP inhibited locomotion, sucrose self-administration and asymptotic operant performance in the BSR paradigm. In vivo microdialysis demonstrated that l-THP slightly elevates extracellular nucleus accumbens DA by itself, but dose-dependently potentiates cocaine-augmented DA, suggesting that a postsynaptic, rather than presynaptic, DA receptor antagonism underlies l-THP's actions on cocaine reward. Together, the present data, combined with previous findings, support the potential use of l-THP for treatment of cocaine addiction.

New developments in the pharmacotherapy of cocaine abuse

Despite huge advances in the neuroscience of substance abuse and dependence in the past 20 years, no approved pharmacological treatment exists for cocaine abuse. The available drugs for the treatment of cocaine abuse are poorly effective, hence the need for new compounds to be screened and tested for efficacy: targeting symptoms might improve the effectiveness of the treatment of cocaine abuse and dependence. On the basis of the known neurochemistry of cocaine, some target compounds have been studied: among others, BP-897, a D3 partial agonist; vanoxerine, a highly selective inhibitor of dopamine uptake; aripiprazole, a partial mixed-action agonist approved for the treatment of schizophrenia. Recently modafinil, approved for the treatment of narcolepsy, proved effective in favouring cocaine abstinence in cocaine-abusing people. Some placebo-controlled studies also reported the effectiveness of topiramate, a licensed antiepileptic drug, and of tiagabine, a gamma-aminobutyric acid (GABA) re-uptake inhibitor also approved as an anticonvulsant; both compounds increased cocaine abstinence with no serious adverse events. Promising results came from two more compounds acting on the GABA circuits, baclofen and valproic acid. Finally disulfiram, prescribed with active psychosocial therapy, was found to favour higher retention rates and longer abstinence periods from both alcohol and cocaine in polydrug-abusing patients. An alternative approach rests on the use of vaccines, to date in the experimental stage still. Psychosocial treatments are a useful companion in the pharmacotherapy of cocaine abuse, with group therapy and contingency management therapies improving motivation and social functioning, particularly in patients abusing alcohol as well.

Antipsychotic drug treatment of schizophrenic patients with substance abuse disorders

BACKGROUND/AIM

In recent years, there has been a growing interest in developing adequate treatments for patients with a diagnosis of schizophrenia and a comorbid substance use disorder (SUD). In the present paper we aim to critically review published reports on the use of conventional and second-generation antipsychotics in the treatment of patients with schizophrenia and comorbid SUD, to provide clinicians with a clearer view of the pharmacological treatment of this highly prevalent dual diagnosis based upon the evidence arising from the scientific literature.

METHODS

A search of the relevant literature from Medline, PsycLIT and EMBASE databases, included in the Science Citation Index, and available up to November 2006 was conducted using the terms: 'schizophrenia', 'substance use disorder' and 'antipsychotics'.

RESULTS

While research on the use of conventional antipsychotics has remained limited, the majority of studies suggest the effectiveness of second-generation antipsychotics, particularly clozapine, for patients with schizophrenia and a comorbid substance use disorder.

CONCLUSION

In the absence of randomized controlled trials that could provide more reliable information, clinical decisions may need to rely on indirect data provided by the increasing number of case reports, open trials and retrospective studies showing a decrease in cigarette smoking, alcohol, cocaine or cannabis use and an improvement of overall psychiatric symptoms.

Manipulation of catechol-O-methyl-transferase (COMT) activity to influence the attenuation of substance seeking behavior, a subtype of Reward Deficiency Syndrome (RDS), is dependent upon gene polymorphisms: A hypothesis

There are common genetic mechanisms responsible for both drug effects and subsequent seeking behavior. In 1996, we coined the term Reward Deficiency Syndrome (RDS). Past and current treatment of substance seeking behavior, a subtype of Reward Deficiency Syndrome (RDS), is considered by most to be inadequate. Recently, we evaluated a complex named Synaptamine [Haveos (SG8839R)]. The main difference with an older studied variant and the latest variant is the inclusion of a proprietary form of Rhodiola rosea, a known catechol-O-methyl-transferase inhibitor (COMT) to potentially enhance the activity of presynaptic released dopamine. In this regard, based on the current literature we hypothesize that manipulation of catechol-O-methyl-transferase (COMT) activity to influence the attenuation of substance seeking behavior, is dependent upon gene polymorphisms. In this regard we hypothesize that carrying the LL genotype with low COMT activity should as theorized, increase the reward induced by substance-induced dopamine release and may indeed increase the propensity to type 1 alcoholism and possibly other drugs that activate the dopaminergic system. Thus when alcohol is present in low COMT LL genotype, increasing COMT activity, not inhibiting it should assist in the reduction of social consumption or abuse. Alternatively, under physiological conditions (no psychoactive substances present (e.g. alcohol) carrying the DRD2 A1 allele with associated low D2 receptors should, as theorized, increase craving behavior because of a low or hypodopaminergic state causing the individual to seek out substances that increase the release of dopamine for subsequent activation of unbound D2 sites in the nucleus accumbens. Thus, in the absence of alcohol or other psychoactive drugs (dopamine releasers), especially during recovery or rehabilitation, decreasing, not increasing COMT activity, should result in enhanced synaptic dopamine as physiologically released, thereby proliferating D2 receptors while reducing stress, increasing well-being, reducing craving behavior and preventing relapse. Based on this hypothesis, we believe that adding the COMT inhibitor R. rosea (as Rhodimin) to our amino-acid and chromium combination in DUI offenders and other illegal drug-related crimes, increases the potential for more targeted neurochemical rebalancing and enhanced relapse prevention. Finally, we hypothesize that these data coupled together provide evidence that the combination of enkephalinase inhibition, neurotransmitter precursor loading, brain tryptophan enhancing and COMT inhibition as well as DNA analysis of the individual's genome, may be useful as an adjunct to therapy when used in outpatient recovery, specifically to assist in reducing craving behavior and preventing relapse.

Quetiapine in patients with comorbid schizophrenia-spectrum and substance use disorders: an open-label trial

BACKGROUND

Preliminary evidence suggests that clozapine relieves the craving for psychoactive substances in schizophrenia patients. Quetiapine shares crucial pharmacological properties with clozapine. Promising results have been described with quetiapine therapy in patients with psychosis and substance use disorder.

METHODS

Based on Diagnostic and Statistical Manual of Mental Disorders - fourth edition (DSM-IV) criteria, patients were diagnosed with comorbid schizophrenia-spectrum and substance use disorders. Patients were switched to quetiapine for a 12-week open-label trial. Craving, quantities used, days of consumption, and severity of substance abuse were assessed every 3 weeks. Alcohol and Drug Use Scales were administered on baseline and end-point. Psychiatric symptoms, depressive symptoms, extrapyramidal symptoms, and cognition were also assessed at baseline, week 6 and week 12.

RESULTS

Twenty-four schizophrenia-spectrum patients were included in the last observation carried forward (LOCF) analyses, responding to one or more of the following substance use disorders: cannabis (15 patients), alcohol (10 patients), and other psychoactive substances (nine patients). Overall, severity of substance abuse improved during the study. Less weekly days were spent on drugs of abuse. A decrease in the weekly Canadian dollars spent on psychoactive substances was also observed. Cognition, psychiatric, depressive, and extrapyramidal symptoms also significantly improved (p < 0.05).

CONCLUSIONS

In this open-label, uncontrolled trial, significant improvements were noted in substance abuse, psychiatric symptoms, extrapyramidal symptoms, and cognition during quetiapine therapy. The study suffered from three main limitations: (1) the open-label design of the study; (2) the patients' poor compliance; and (3) the small sample size involved. Controlled studies on the use of quetiapine in dual diagnosis schizophrenia are warranted to confirm that the effects are drug-related.

EFFECTS OF ARIPIPRAZOLE ON ALCOHOL INTAKE IN AN ANIMAL MODEL OF HIGH-ALCOHOL DRINKING

AIMS

This study examined the effects of aripiprazole, a novel atypical antipsychotic drug with partial agonist properties at dopamine D2 receptors, on the voluntary limited access alcohol drinking of alcohol-preferring AA (Alko, Alcohol) rats.

METHODS

AA rats were taught to drink 10% alcohol in a 4 h limited access paradigm. Effects of acute aripiprazole (0, 0.3, 1.0, and 3.0 mg/kg) on the limited access alcohol drinking were studied. In repeated treatment experiment, aripiprazole (0, 1.0, and 6.0 mg/kg) was administered once daily over five successive days. To reveal any effect by aripiprazole not selective for alcohol drinking, 0.025% saccharin solution was substituted for alcohol during the 4 h limited access, and acute treatments were repeated. The effects of aripiprazole on ambulatory locomotor activity were tested with doses that were used in the acute experiments.

RESULTS

Acute aripiprazole at the doses of 0.3, 1.0, and 3.0 mg/kg had no effect on alcohol drinking. Repeated treatment with the aripiprazole dose of 6.0 mg/kg significantly diminished alcohol drinking at the 1 h time point. This dose had no effect on saccharin drinking when given acutely. Acute aripiprazole at the doses of 1.0, 3.0, and 6.0 mg/kg significantly suppressed locomotor activity.

CONCLUSIONS

Aripiprazole decreased limited access alcohol drinking in AA rats, but only at a high dose that also strongly suppressed locomotor activity.

Alcohol drinking of alcohol-preferring AA rats is differentially affected by clozapine and olanzapine

Clinical evidence suggests that atypical antipsychotic drugs might reduce alcohol drinking and help to maintain abstinence. This study aimed to compare the effects of two widely used atypical antipsychotic drugs clozapine and olanzapine on alcohol intake in alcohol-preferring AA (Alko, Alcohol) rats that were taught to drink 10% alcohol in a 4 h limited access paradigm. Effects of acute clozapine (0, 0.3, 1.0 and 5.0 mg/kg) and olanzapine (0, 0.1, 0.5 and 1.25 mg/kg) treatments on the limited access alcohol drinking were studied. In repeated treatment experiment, clozapine (1.0 mg/kg) or olanzapine (0.5 mg/kg) was administered once daily, before limited access alcohol drinking session, over 5 successive days. To reveal any effect of the drugs selective for alcohol drinking, alcohol was exchanged with 0.1% saccharin solution for the 4 h limited access, and acute treatments were repeated. Effects of the drugs on ambulatory locomotor activity were tested with doses that were used in the acute experiments. Acute clozapine treatment had no effect on either alcohol or saccharin drinking, but olanzapine significantly reduced 4 h alcohol drinking. Repeated olanzapine treatment significantly reduced 4 h alcohol drinking when compared with vehicle or clozapine, but a tolerance developed to this effect. Repeated clozapine treatment produced no significant effect compared with vehicle. Both drugs significantly reduced locomotor activity. In conclusion, the atypical antipsychotic olanzapine non-selectively reduced alcohol drinking, while clozapine failed to do so, even if both were administered at pharmacologically effective doses.

Agents in Development for the Management of Cocaine Abuse

Cocaine abuse is a serious health problem in many areas of the world, yet there are no proven effective medications for the treatment of cocaine dependence. Preclinical studies suggest that the reinforcing effect of cocaine that promotes its abuse is mediated by blockade of the presynaptic dopamine transporter. This results in increased dopamine activity in the mesolimbic or meso-accumbens dopamine reward system of brain. Development of new medications to treat cocaine dependence has focused on manipulation of this dopamine system, either by direct action on dopamine binding sites (transporter or receptors) or indirectly by affecting other neurotransmitter systems that modulate the dopamine system. In principle, a medication could act via one of three mechanisms: (i) as a substitute for cocaine by producing similar dopamine effects; (ii) as a cocaine antagonist by blocking the binding of cocaine to the dopamine transporter; or (iii) as a modulator of cocaine effects by acting at other than the cocaine binding site. The US National Institute on Drug Abuse has a Clinical Research Efficacy Screening Trial (CREST) programme to rapidly screen existing medications. CREST identified four medications warranting phase II controlled clinical trials: cabergoline, reserpine, sertraline and tiagabine. In addition, disulfiram and selegiline (deprenyl) have been effective and well tolerated in phase II trials. However, selegiline was found ineffective in a recent phase III trial. Promising existing medications probably act via the first or third aforementioned mechanisms. Sustained-release formulations of stimulants such as methylphenidate and amfetamine (amphetamine) have shown promise in a stimulant substitution approach. Disulfiram and selegiline increase brain dopamine concentrations by inhibition of dopamine-catabolising enzymes (dopamine-beta-hydroxylase and monoamine oxidase B, respectively). Cabergoline is a direct dopamine receptor agonist, while reserpine depletes presynaptic stores of dopamine (as well as norepinephrine and serotonin). Sertraline, baclofen and vigabatrin indirectly reduce dopamine activity by increasing activity of neurotransmitters (serotonin and GABA) that inhibit dopamine activity. Promising new medications act via the second or third aforementioned mechanisms. Vanoxerine is a long-acting inhibitor of the dopamine transporter which blocks cocaine binding and reduces cocaine self-administration in animals. Two dopamine receptor ligands that reduce cocaine self-administration in animals are also undergoing phase I human safety trials. Adrogolide is a selective dopamine D(1) receptor agonist; BP 897 is a D(3) receptor partial agonist.A pharmacokinetic approach to treatment would block the entry of cocaine into the brain or enhance its catabolism so that less cocaine reached its site of action. This is being explored in animals using the natural cocaine-metabolising enzyme butyrylcholinesterase (or recombinant versions with enhanced capabilities), catalytic antibodies, and passive or active immunisation to produce anti-cocaine binding antibodies. A recent phase I trial of a "cocaine vaccine" found it to be well tolerated and producing detectable levels of anti-cocaine antibodies for up to 9 months after immunisation.

Drug craving and addiction: integrating psychological and neuropsychopharmacological approaches

In the present review, an integrated approach to craving and addiction is discussed, which is based on recent insights from psychology and neuropsychopharmacology. An integrated model explains craving and relapse in humans by the psychological mechanism of "attentional bias" and provides neuropsychopharmacological mechanisms for this bias. According to this model, cognitive processes mediate between drug stimulus and the subject's response to this stimulus and subsequent behavioral response (e.g., drug use, relapse). According to the model, a conditioned drug stimulus produces an increase in dopamine levels in the corticostriatal circuit, in particular the anterior cingulate gyrus, amygdala, and nucleus accumbens, which in turn serves to draw the subject's attention towards a perceived drug stimulus. This process results in motor preparation and a hyperattentive state towards drug-related stimuli that, ultimately, promotes further craving and relapse. Evidence for this attentional bias hypothesis is reviewed from both the psychopharmacological and the neuroanatomical viewpoints. The attentional bias hypothesis raises several suggestions for clinical approaches and further research.

Risperidone reduces limited access alcohol drinking in alcohol-preferring rats

An atypical antipsychotic drug risperidone reduced ethanol drinking of ethanol-preferring Alko, Alcohol (AA) rats in a limited access paradigm. Its effect was transient at a dose known to preferentially antagonize the 5-HT(2) receptors (0.1 mg/kg, s.c.), but long-lasting when the dose was increased to 1.0 mg/kg that also blocks dopamine D(2) receptors. Risperidone also reduced dose-dependently locomotor activity and limited access saccharin intake of the AA rats, indicating that its effect on ethanol drinking was not selective. Risperidone at 0.1 mg/kg given before four successive daily ethanol-drinking sessions significantly reduced the ethanol intake. These data from an animal model of high ethanol intake suggest that risperidone should be tested in various populations of alcoholics for reducing ethanol consumption.

Rapid assessment of choice between cocaine and food in rhesus monkeys: effects of environmental manipulations and treatment with d-amphetamine and flupenthixol

The present study describes a procedure that permits rapid assessment of environmental and pharmacological factors that may influence the choice between cocaine and food in rhesus monkeys. Daily 2 h sessions were divided into five components. During each component, monkeys (N=4) chose between i.v. cocaine (0-0.1 mg/kg/injection) and food (0, 1, or 3 food pellets). Up to 10 reinforcers were available during each component, and different discriminative stimuli were associated with each magnitude of each reinforcer. Cocaine choice was directly related to cocaine dose, and a cocaine choice dose-effect curve could be determined in a single experimental session. The choice between cocaine and food was influenced by the schedules of cocaine and food reinforcement, the magnitude of the food reinforcer, and the amount of noncontingent food provided outside the experimental session. These results confirm and extend previous findings with other choice procedures and validate the sensitivity of the present procedure to environmental manipulations. The choice between cocaine and food could also be influenced by treatment with candidate pharmacotherapies for cocaine abuse and dependence. The "agonist" medication d-amphetamine produced rightward shifts in the cocaine choice dose-effect curve and decreased cocaine choice, whereas the "antagonist" medication flupenthixol had little effect on cocaine choice. Overall, these results suggest that this choice procedure may be useful for the evaluation of both environmental determinants of cocaine use and candidate pharmacotherapies for the treatment of cocaine abuse.

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.

Effect of flupenthixol on subjective and cardiovascular responses to intravenous cocaine in humans

The effects of oral flupenthixol and intramuscular (i.m.) flupenthixol decanoate in combination with intravenous (i.v.) cocaine were evaluated in male cocaine abusers. Participants resided at an inpatient research unit for 27 days followed by an 11-day outpatient period. Oral flupenthixol (2.5 or 5.0 mg; p.o.) followed by flupenthixol decanoate (10 or 20 mg; i.m.) and placebo were investigated in individuals who were randomly assigned to one of three groups under double-blind conditions (placebo, low or high dose flupenthixol). During the inpatient period, participants had four fixed cocaine dosing sessions; each session they were administered four doses of i.v. cocaine (approx. 48 mg/70 kg), spaced 14 min apart. These sessions occurred once before medication (baseline phase), once following oral medication (oral phase), and twice following intramuscular medication (IM phase). Out of 23 participants, 18 completed the study; 4 of the 5 non-completers were in the high dose flupenthixol group. Overall, there were few subjective, cardiovascular, or cocaine pharmacokinetic differences between the placebo group and the low dose flupenthixol group, indicating that the low dose of flupenthixol was well tolerated, but ineffective. In the high dose flupenthixol group, two out of seven individuals (29%) experienced a dystonic reaction following oral flupenthixol and were medically discharged. Taken together, these findings indicate that flupenthixol is not a good candidate for treating cocaine abusers.