Buprenorphine + naloxone plus naltrexone for the treatment of cocaine dependence: the Cocaine Use Reduction with Buprenorphine (CURB) study

AIMS

To examine the safety and effectiveness of buprenorphine + naloxone sublingual tablets (BUP, as Suboxone(®) ) provided after administration of extended-release injectable naltrexone (XR-NTX, as Vivitrol(®) ) to reduce cocaine use in participants who met DSM-IV criteria for cocaine dependence and past or current opioid dependence or abuse.

METHODS

This multi-centered, double-blind, placebo-controlled study, conducted under the auspices of the National Drug Abuse Treatment Clinical Trials Network, randomly assigned 302 participants at sites in California, Oregon, Washington, Colorado, Texas, Georgia, Ohio, New York and Washington DC, USA to one of three conditions provided with XR-NTX: 4 mg/day BUP (BUP4, n = 100), 16 mg/day BUP (BUP16, n = 100, or no buprenorphine (placebo; PLB, n = 102). Participants received pharmacotherapy for 8 weeks, with three clinic visits per week. Cognitive behavioral therapy was provided weekly. Follow-up assessments occurred at 1 and 3 months post-intervention. The planned primary outcome was urine drug screen (UDS)-corrected, self-reported cocaine use during the last 4 weeks of treatment. Planned secondary analyses assessed cocaine use by UDS, medication adherence, retention and adverse events.

RESULTS

No group differences were found between groups for the primary outcome (BUP4 versus PLB, P = 0.262; BUP16 versus PLB, P = 0.185). Longitudinal analysis of UDS data during the evaluation period using generalized linear mixed equations found a statistically significant difference between BUP16 and PLB [P = 0.022, odds ratio (OR) = 1.71] but not for BUP4 (P = 0.105, OR = 1.05). No secondary outcome differences across groups were found for adherence, retention or adverse events.

CONCLUSIONS

Buprenorphine + naloxone, used in combination with naltrexone, may be associated with reductions in cocaine use among people who meet DSM-IV criteria for cocaine dependence and past or current opioid dependence or abuse.

Achieving cannabis cessation -- evaluating N-acetylcysteine treatment (ACCENT): design and implementation of a multi-site, randomized controlled study in the National Institute on Drug Abuse Clinical Trials Network

Despite recent advances in behavioral interventions for cannabis use disorders, effect sizes remain modest, and few individuals achieve long-term abstinence. One strategy to enhance outcomes is the addition of pharmacotherapy to complement behavioral treatment, but to date no efficacious medications targeting cannabis use disorders in adults through large, randomized controlled trials have been identified. The National Institute on Drug Abuse Clinical Trials Network (NIDA CTN) is currently conducting a study to test the efficacy of N-acetylcysteine (NAC) versus placebo (PBO), added to contingency management, for cannabis cessation in adults (ages 18-50). This study was designed to replicate positive findings from a study in cannabis-dependent adolescents that found greater odds of abstinence with NAC compared to PBO. This paper describes the design and implementation of an ongoing 12-week, intent-to-treat, double-blind, randomized, placebo-controlled study with one follow-up visit four weeks post-treatment. Approximately 300 treatment-seeking cannabis-dependent adults will be randomized to NAC or PBO across six study sites in the United States. The primary objective of this 12-week study is to evaluate the efficacy of twice-daily orally-administered NAC (1200 mg) versus matched PBO, added to contingency management, on cannabis abstinence. NAC is among the first medications to demonstrate increased odds of abstinence in a randomized controlled study among cannabis users in any age group. The current study will assess the cannabis cessation efficacy of NAC combined with a behavioral intervention in adults, providing a novel and timely contribution to the evidence base for the treatment of cannabis use disorders.

Strategies for safety reporting in substance abuse trials

BACKGROUND

Reporting all adverse events (AEs) and serious adverse events (SAEs) in substance use disorder (SUD) clinical trials has yielded limited relevant safety information and has been burdensome to research sites.

OBJECTIVE

This article describes a new strategy utilizing standard data elements for AE and SAEs that defines a threshold to reduce unnecessary safety reporting burden in SUD clinical trials and describes retrospective review and prospective preliminary data on the strategy's safety reporting impact.

METHODS

We developed a new strategy to standardize safety reporting and tailor reporting to the trial intervention risk. Protocols and safety data from 17 SUD clinical trials were reviewed. Retrospective analysis of five of these studies and prospective application to new studies is described.

RESULTS

Across the 17 previously completed trials, a total of 11,220 AEs and 1330 SAEs were reported in the 6737 participants. Wide variability in AE and SAE reporting rates were noted based on trial type and inconsistent reporting strategies. Application of the new, tailored safety strategy retrospectively and prospectively reduces reporting burden of irrelevant safety events.

CONCLUSION

Comparison of the previous reporting strategies used in SUD trials to the new strategy demonstrates a more consistent safety system with a reduction in safety reporting burden while maintaining appropriate safety monitoring.

SCIENTIFIC SIGNIFICANCE

Safety assessments should be tailored to the participant risks based on the trial intervention. The current strategies could be applied to safety assessments across all clinical trials in SUDs.

Pharmacological dissociation of the motor and electrical aspects of convulsive status epilepticus induced by the cholinesterase inhibitor soman

In an effort to validate methods to be used in a screen for drugs effective as anticonvulsants for soman-induced convulsions, scopolamine (0.2 mg/kg) or diazepam (1 mg/kg) were given (i.m.) to male guinea pigs as a pretreatment 30 min before a convulsant dose of soman. Pyridostigmine, atropine and pralidoxime chloride also were given to counteract the lethality of soman. All animals challenged with soman and which did not receive either diazepam or scopolamine exhibited convulsive status epilepticus (SE), identified by continuous electrographic seizure activity (EGSA) and continuous motor convulsions. Despite the presence of continuous motor convulsions in all animals pretreated with diazepam and challenged with soman, EGSA was not observed in five of the seven animals. Continuous motor convulsions developed in four of seven animals pretreated with scopolamine and challenged with soman, but EGSA was not observed in any scopolamine-pretreated guinea pig. Neuronal necrosis was observed in the hippocampus, thalamus, amygdala, and cerebral and pyriform cortices in each animal with EGSA, but not brain damage was found in subjects without EGSA. Thus, although convulsions, EGSA and brain damage normally occur together in animals exposed to soman, the convulsions can be pharmacologically dissociated from the EGSA and brain damage, demonstrating that the clinically manifested convulsions are not dependent on EGSA recorded from the cortex or on abnormal activity which leads to neuronal necrosis in the forebrain.

Local norepinephrine depletion and learning-related neuronal activity in cingulate cortex and anterior thalamus of rabbits

Multi-unit neuronal activity was recorded in posterior cingulate cortex (area 29) and the anterior ventral (AV) thalamic nucleus during discriminative instrumental avoidance learning wherein a response (stepping in an activity wheel) to a 0.5-s tone (CS+) prevented a foot-shock 5 s after CS+ onset. Presentations of a different tone (CS-) on 50% of the conditioning trials in an irregular sequence with the CS+ did not predict shock and thus required no response. Two groups of rabbits received intracranial micro-injections of 6-hydroxydopamine (6-OHDA) to locally deplete the NE in area 29 or the AV nucleus. Vehicle was injected in the non-depleted area in each group and a third group received vehicle injections in both areas. Dopamine neurons in subjects that received 6-OHDA were protected by pre-treatment with GBR-12909. Neuronal data were collected during two pre-training sessions in response to the tones only and when the tones and shock were presented unpaired. Thalamically depleted rabbits made more, and cortically depleted rabbits made fewer, avoidance responses than controls during the early stages of behavioral acquisition, and cortically depleted rabbits made fewer responses than controls and thalamically depleted rabbits during extinction testing administered after the completion of acquisition. One effect of NE depletion on neuronal activity was entirely local: elimination of neuronal sensitization effects (enhanced discharges elicited by tones during the unpaired tone-shock pre-training treatment relative to pre-training with tones only). Other neuronal effects of NE depletion were system-wide, i.e., they occurred whether the depletion was cortical or thalamic.(ABSTRACT TRUNCATED AT 250 WORDS)

Dizocilpine (MK-801) arrests status epilepticus and prevents brain damage induced by soman

The involvement of the NMDA receptor in the neurotoxicity induced by soman, an organophosphorus compound which irreversibly inhibits cholinesterase, was studied in guinea pigs. The drug MK-801 (0.5, 1 or 5 mg/kg, i.p.) was given as a pretreatment before a convulsant dose of soman or as a posttreatment (30, 100 or 300 micrograms/kg, i.m.) 5 min after the development of soman-induced status epilepticus. Pyridostigmine, atropine and pralidoxime chloride were also given to each subject to counteract the lethality of soman. All subjects that were challenged with soman and given the vehicle for MK-801 (saline) exhibited severe convulsions and electrographic seizure activity. Neuronal necrosis was found in the hippocampus, amygdala, thalamus and the pyriform and cerebral cortices of those subjects surviving for 48 hr. Pretreatment with 0.5 or 1 mg/kg doses of MK-801 did not prevent nor delay the onset of seizure activity but did diminish its intensity and led to its early arrest. At the largest dose (5 mg/kg), MK-801 completely prevented the development of seizure activity and brain damage. Posttreatment with MK-801 prevented, arrested or reduced seizure activity, convulsions and neuronal necrosis in a dose-dependent manner. The NMDA receptor may play a more critical role in the spread and maintenance, rather than the initiation of cholinergically-induced seizure activity.

Effects of cingulate cortical lesions on avoidance learning and training-induced unit activity in rabbits

This study extends an ongoing analysis of the neural mediation of discriminative avoidance learning in rabbits. Electrolytic lesions encompassing anterior and posterior cingulate cortex (area 24 and 29) or ibotenic acid lesions in area 24 only were made prior to avoidance conditioning wherein rabbits learned to step in response to a tone conditional stimulus (CS+) in order to avoid a brief, response-terminated 1.5 mA. foot-shock unconditional stimulus (US). The US was presented 5 s after CS+ onset, in the absence of a prior stepping response. The rabbits also learned to ignore a different tone (CS-) not followed by the US. Multi-unit activity of the caudate and medial dorsal (MD) thalamic nuclei, projection targets of the cingulate cortex, was recorded during learning in all rabbits. Activity was also recorded in area 29 in the rabbits with area 24 lesions. Learning in rabbits with combined lesions was severely impaired and it was moderately retarded after lesions in area 24. MD thalamic and caudate training-induced neuronal discharge increments elicited by the CS+ were enhanced in rabbits with lesions, suggesting a suppressive influence of cingulate cortical projections on this activity. Early-, but not late-developing training-induced unit activity in area 29c/d was absent in rabbits with area 24 lesions, indicating that area 24 is a source of early-developing area 29 plasticity. These results are consistent with hypotheses of a theoretical working model, stating that: a) learning depends on the integrity of two functional systems, a mnemonic recency system comprised by circuitry involving area 24 and the MD nucleus and a mnemonic primacy system comprised by circuitry involving area 29 and the anterior thalamic nuclei; b) corticothalamic information flow in these systems suppresses thalamic CS elicited activity in trained rabbits; c) corticostriatal information flow is involved in avoidance response initiation. An absence of rhythmic theta-like neuronal bursts in area 29b in rabbits with area 24 lesions is attributable to passing fiber damage.

Neuronal encoding of conditional stimulus duration in the cingulate cortex and the limbic thalamus of rabbits

Neuronal activity in cingulate cortex was recorded during discriminative active avoidance conditioning of rabbits. In one subpopulation of neurons, brief (200 and 500 ms) conditional stimuli (CSs) elicited greater average cingulate cortical training-induced neuronal discharges during conditioned response acquisition than did a long (5,000 ms) CS, and the amount of neuronal discrimination between CS+ and CS- was greater in response to the brief CSs than to the long CS. Neurons in a different subpopulation did not encode CS duration per se but were sensitive to the novelty of the CS duration. Medial dorsal and anteroventral thalamic neurons were suppressed by novel CS durations that activated novelty-sensitive neurons in related cingulate cortical areas. These results are discussed in relation to a theoretical model of the neural mediation of avoidance conditioning.

Conditional stimulus probability and activity of hippocampal, cingulate cortical, and limbic thalamic neurons during avoidance conditioning in rabbits

Past studies of the neuronal correlates of avoidance conditioning in rabbits have led to a model of information flow among structures of the limbic system. A hypothesis of the model is that unexpected stimuli activate certain hippocampal and cingulate cortical neurons. This activity in turn suppresses or "limits" the firing of limbic thalamic neurons. This hypothesis is tested in relation to stimuli classified as unexpected or expected on the basis of their incidence or "probability." Multi-unit and field potential responses in the anterior and posterior cingulate cortices (AC and PC), the dentate gyrus (DG), and the anterior ventral (AV) and medial dorsal (MD) thalamic nuclei were recorded during the acquisition and performance of a locomotor conditioned response (CR). The CR, stepping in an activity wheel in response to a 0.5-s tone (CS+), prevented the occurrence of a shock US scheduled 5 s after CS+ onset. The rabbits also learned to ignore a different tone (CS-), not predictive of the US. Training was given daily (120 trials, 60 with each CS in an irregular sequence) until behavioral discrimination reached criterion. After criterion, asymmetric probability (AP) sessions were given, in which the CS+/CS- proportions were .2/.8 or .8/.2. The AP sessions were the same as conditioning sessions except for the probability manipulation. A significant discriminative response, i.e., a greater neuronal discharge to the CS+ than to the CS-, developed in all regions during behavioral acquisition. The unit response in the AP sessions was enhanced in all areas by rare presentation of the CS-, compared with the equal and frequent CS- conditions. Rare presentation of the CS+ enhanced the unit response in the cortical areas (AC, PC, and DG), but it suppressed the firing of limbic thalamic (AV and MD) neurons. These results were supportive of the model. Rare CS+ presentations did not alter AV and PC neuronal activity in rabbits with subicular lesions, a result suggesting that an intact hippocampus is essential for normal neuronal responses to stimulus probability in the cingulate cortex and limbic thalamus.

MK-801 protects against seizures induced by the cholinesterase inhibitor soman

MK-801, a novel anticonvulsant which is a potent N-methyl-d-aspartate antagonist, attenuated or blocked seizures and convulsions induced by the irreversible organophosphorus anticholinesterase inhibitor soman. Guinea pigs chronically instrumented for electrocorticogram recording were given a low dose (1 mg/kg) or a high dose (5 mg/kg) of MK-801 or saline vehicle 30 min prior to receiving 2 x LD50 of soman. All animals were treated with atropine methylnitrate and pralidoxime chloride 30 sec after soman injection. All saline control subjects exhibited severe seizures and convulsions shortly after receiving soman. Low dose MK-801 greatly attenuated and high dose MK-801 completely blocked seizure activity. Animals treated with MK-801 recovered faster and had a much greater probability of survival for 48 hr after soman exposure than did controls. This is the first demonstration of the involvement of the excitatory amino acid neurotransmitter system in seizures and convulsions induced by a cholinesterase inhibitor.

Anterior and medial thalamic lesions, discriminative avoidance learning, and cingulate cortical neuronal activity in rabbits

Four groups of male albino rabbits were trained to perform a conditioned response (CR, stepping in an activity wheel) to an acoustic (pure tone) conditional stimulus (CS+). A 1.5-2.0 mA shock unconditional stimulus (US) delivered through the grid floor of the wheel was administered 5 s after CS+ onset, but stepping during the CS-US interval prevented the US. The rabbits were also trained to ignore a second tone (a negative conditional stimulus or CS-) of different auditory frequency than the CS+, that was presented in an irregular order on half of the conditioning trials but never followed by the US. One group had bilateral electrolytic lesions in the medial dorsal (MD) thalamic nucleus, a second group had combined bilateral lesions in the MD and the anterior thalamic nuclei, and a third group had no lesions. The fourth group was composed of rabbits with combined lesions that resulted in only partial damage in the anterior and MD nuclei. In all rabbits, multi-unit activity and field potentials were recorded from the cingulate cortical projection targets of the MD and anterior nuclei. The average rate of acquisition in rabbits with MD and partial lesions was not significantly different from that in controls, but the asymptotic performance in rabbits with lesions was significantly impaired, relative to that in controls. None of the rabbits that had the combined MD and anterior thalamic lesions reached the acquisition criterion. The average proportion of trials in which these rabbits performed avoidance responses during their final training sessions was 0.3, compared to 0.8 in controls. The unconditioned response was not significantly affected by the lesions, nor was there any indication that the lesions impaired the sensory processing of the CSs. These results and the massive training-induced neuronal discharges shown in past studies to occur in the limbic thalamic neurons indicate that these neurons are importantly involved in the circuitry that mediates discriminative avoidance conditioning in rabbits. The training-induced neuronal activity in cingulate cortex was dramatically attenuated in rabbits with lesions. Differences in the degree of this attenuation between lesion conditions and with respect to training stages were discussed in relation to a theoretical working model of limbic thalamic and cingulate cortical associative functions.

Conditional stimulus probability and activity of hippocampal, cingulate cortical, and limbic thalamic neurons during avoidance conditioning in rabbits

Past studies of the neuronal correlates of avoidance conditioning in rabbits have led to a model of information flow among structures of the limbic system. A hypothesis of the model is that unexpected stimuli activate certain hippocampal and cingulate cortical neurons. This activity in turn suppresses or "limits" the firing of limbic thalamic neurons. This hypothesis is tested in relation to stimuli classified as unexpected or expected on the basis of their incidence or "probability." Multi-unit and field potential responses in the anterior and posterior cingulate cortices (AC and PC), the dentate gyrus (DG), and the anterior ventral (AV) and medial dorsal (MD) thalamic nuclei were recorded during the acquisition and performance of a locomotor conditioned response (CR). The CR, stepping in an activity wheel in response to a 0.5-s tone (CS+), prevented the occurrence of a shock US scheduled 5 s after CS+ onset. The rabbits also learned to ignore a different tone (CS-), not predictive of the US. Training was given daily (120 trials, 60 with each CS in an irregular sequence) until behavioral discrimination reached criterion. After criterion, asymmetric probability (AP) sessions were given, in which the CS+/CS- proportions were .2/.8 or .8/.2. The AP sessions were the same as conditioning sessions except for the probability manipulation. A significant discriminative response, i.e., a greater neuronal discharge to the CS+ than to the CS-, developed in all regions during behavioral acquisition. The unit response in the AP sessions was enhanced in all areas by rare presentation of the CS-, compared with the equal and frequent CS- conditions. Rare presentation of the CS+ enhanced the unit response in the cortical areas (AC, PC, and DG), but it suppressed the firing of limbic thalamic (AV and MD) neurons. These results were supportive of the model. Rare CS+ presentations did not alter AV and PC neuronal activity in rabbits with subicular lesions, a result suggesting that an intact hippocampus is essential for normal neuronal responses to stimulus probability in the cingulate cortex and limbic thalamus.

Posterior cingulate cortical lesions eliminate learning-related unit activity in the anterior cingulate cortex

The frequency of multi-unit neuronal firing in response to tonal conditional stimuli increases, and the neuronal responses become discriminative in character, in the anterior and posterior subfields of the cingulate cortex (Brodmann's Area 24 and 29, respectively) during the course of discriminative avoidance conditioning in rabbits. Bilateral electrolytic lesions of the dorsal subicular complex eliminated the training-induced excitatory response in both cortical subfields, suggesting that subiculocortical projection fibers are essential for this effect. Yet, available data indicate that the subicular projection reaches only Area 29, not Area 24. Here we test the hypothesis that the subicular influence attains Area 24 via a synaptic relay in Area 29. The results showed in keeping with the hypothesis, that bilateral aspirative or electrolytic lesions in Area 29 eliminated the training-induced neuronal responses in Area 24. As in the case of subicular lesions, the Area 29 lesions increased the amplitude of the macropotentials in Area 24. These results are discussed in relation to a model of the interactions of the cingulate cortex, hippocampus and the limbic thalamic nuclei during learning.

Anterior thalamic discriminative neuronal responses enhanced during learning in rabbits with subicular and cingulate cortical lesions

The neuronal discharge that develops in the anterior ventral thalamic nucleus (AVN) in response to a task-relevant stimulus during learning is enhanced in rabbits with damage in the cingulate and subicular (hippocampal) cortical areas that project to this nucleus. These results indicate that the corticothalamic projections limit the anterior thalamic response but they do not appear to contribute causally to its development. Thus, the discriminative neuronal response is owed to interactions that occur wholly within the subcortical domain of the AVN. The production of this neural code for significant stimuli may be the principal function of the AVN. The enhanced thalamic discharges may be a neural cause of behavioral hyperactivity in animals and amnesia in humans with hippocampal damage.

Anterior thalamic lesions and neuronal activity in the cingulate and retrosplenial cortices during discriminative avoidance behavior in rabbits

Bilateral electrolytic lesions of the anteroventral (AV) nucleus of the thalamus given after training impaired retention performance (extinction and reacquisition) of rabbits in a differential avoidance conditioning task. In addition, the lesions abolished the excitatory, discriminative multiple-unit discharges that had developed in the cingulate and retrosplenial cortices to the auditory conditional stimuli (CSs) during the course of behavioral acquisition, prior to the induction of the lesions. The excitatory discharges were supplanted in the subjects with lesions by CS-elicited reduction of neuronal firing to levels below the prestimulus baseline. Lesions given before training did not disrupt behavioral acquisition, but they did eliminate the excitatory tone-elicited neuronal discharges that normally occur in the cortex before and during training. The CS-elicited reduction of neuronal firing did not occur at the beginning of training in the subjects given lesions before training, but it developed during the course of training. The lesions did not eliminate the excitatory and discriminative neuronal activity of the prefrontal cortex. These results demonstrate that excitatory and discriminative neuronal discharges in the cingulate and retrosplenial cortices are critically dependent on the connections of these areas with the anterior thalamic nuclei. Also the lesion-induced disruption of performance during extinction and reacquisition but not during original learning confirms a prediction from past electrophysiological studies, that the AV thalamic nucleus is involved in the mediation of the maintenance and retention of the conditioned avoidance behavior, but not in its original acquisition.

Anterior thalamic lesions and neuronal activity in the cingulate and retrosplenial cortices during discriminative avoidance behavior in rabbits

Bilateral electrolytic lesions of the anteroventral (AV) nucleus of the thalamus given after training impaired retention performance (extinction and reacquisition) of rabbits in a differential avoidance conditioning task. In addition, the lesions abolished the excitatory, discriminative multiple-unit discharges that had developed in the cingulate and retrosplenial cortices to the auditory conditional stimuli (CSs) during the course of behavioral acquisition, prior to the induction of the lesions. The excitatory discharges were supplanted in the subjects with lesions by CS-elicited reduction of neuronal firing to levels below the prestimulus baseline. Lesions given before training did not disrupt behavioral acquisition, but they did eliminate the excitatory tone-elicited neuronal discharges that normally occur in the cortex before and during training. The CS-elicited reduction of neuronal firing did not occur at the beginning of training in the subjects given lesions before training, but it developed during the course of training. The lesions did not eliminate the excitatory and discriminative neuronal activity of the prefrontal cortex. These results demonstrate that excitatory and discriminative neuronal discharges in the cingulate and retrosplenial cortices are critically dependent on the connections of these areas with the anterior thalamic nuclei. Also the lesion-induced disruption of performance during extinction and reacquisition but not during original learning confirms a prediction from past electrophysiological studies, that the AV thalamic nucleus is involved in the mediation of the maintenance and retention of the conditioned avoidance behavior, but not in its original acquisition.