Alcohol intoxication does not change [11C]cocaine pharmacokinetics in human brain and heart

Cardiovascular Risks of Simultaneous Use of Alcohol and Cocaine-A Systematic Review

Background: The simultaneous use of cocaine and alcohol is highly prevalent and is associated with high numbers of emergency department admissions, primarily due to cardiovascular complications. Aims: To answer the question of whether the co-use of cocaine and alcohol increases the cardiovascular risk compared to the use of cocaine alone. Method: A systematic review of human studies comparing the cardiovascular risk of co-used cocaine and alcohol with the use of cocaine alone. Results: Despite a higher myocardial workload induced by the co-use of cocaine and alcohol and the potentiation of cocaine's cardiovascular effects by alcohol, the findings on the risk and severity of cardiovascular symptoms due to combined use are inconsistent. However, the co-use of cocaine and alcohol clearly leads to higher mortality. Interestingly, the presence of cocaethylene, a unique metabolite generated only via a pharmacokinetic interaction between alcohol and cocaine, carries an 18- to 25-fold increase over the absence of cocaethylene (cocaine-alone users) in the risk of sudden death and is associated with myocardial injury and cardiac arrest, probably due to the inhibition of cardiac ion channels by cocaethylene. Conclusion: Despite the inconsistency in some of the results, it is concluded that the co-use of cocaine and alcohol poses an additional risk of cardiovascular fatalities compared to the use of cocaine alone.

Radiosynthesis, Preclinical, and Clinical Positron Emission Tomography Studies of Carbon-11 Labeled Endogenous and Natural Exogenous Compounds

The presence of positron emission tomography (PET) centers at most major hospitals worldwide, along with the improvement of PET scanner sensitivity and the introduction of total body PET systems, has increased the interest in the PET tracer development using the short-lived radionuclides carbon-11. In the last few decades, methodological improvements and fully automated modules have allowed the development of carbon-11 tracers for clinical use. Radiolabeling natural compounds with carbon-11 by substituting one of the backbone carbons with the radionuclide has provided important information on the biochemistry of the authentic compounds and increased the understanding of their in vivo behavior in healthy and diseased states. The number of endogenous and natural compounds essential for human life is staggering, ranging from simple alcohols to vitamins and peptides. This review collates all the carbon-11 radiolabeled endogenous and natural exogenous compounds synthesised to date, including essential information on their radiochemistry methodologies and preclinical and clinical studies in healthy subjects.

Cocaine influences alcohol-seeking behavior and relapse drinking in alcohol-preferring (P) rats

BACKGROUND

The results of several studies suggest that there may be common neurocircuits regulating drug-seeking behaviors. Common biological pathways regulating drug-seeking would explain the phenomenon that seeking for 1 drug can be enhanced by exposure to another drug of abuse. The objective of this study was to assess the time course effects of acute cocaine administration on ethanol (EtOH) seeking and relapse.

METHODS

Alcohol-preferring (P) rats were allowed to self-administer 15% EtOH and water. EtOH-seeking was assessed through the use of the Pavlovian spontaneous recovery (PSR) model, while EtOH-relapse drinking was assessed through the use of the alcohol-deprivation effect.

RESULTS

Cocaine (0, 1, or 10 mg/kg), injected immediately, 30 minutes, or 4 hours prior to the first PSR testing session, dose-dependently increased responding on the EtOH lever compared to extinction responses and responding by saline controls. Under relapse conditions, cocaine given immediately prior to the relapse session had no effect (1 mg/kg) or reduced responding (10 mg/kg). In contrast, cocaine given 4 hours prior to the relapse session markedly enhanced EtOH responding compared to saline.

CONCLUSIONS

The enhanced expression of EtOH-seeking and EtOH-relapse behaviors may be a result of a priming effect of cocaine on neuronal circuits mediating these behaviors. The effect of cocaine on EtOH-relapse drinking is indicative of the complex interactions that can occur between drugs of abuse; production of conflicting behaviors (immediate), and priming of relapse/seeking (4-hour delay).

Modulation of cocaine-induced place preferences by alcohol

Behavioral and physiological evidence suggests that alcohol modulates the effects produced by cocaine. To assess whether such modulation is evident with cocaine's affective properties, the present studies examined the effects of alcohol on cocaine-induced conditioned place preferences (CPP). In Experiment 1, male Sprague-Dawley rats were assigned to one of three groups based on whether they were conditioned with 20 mg/kg cocaine (Group C), 0.5 g/kg alcohol (Group A), or the combination (Group C/A). On the first conditioning trial, animals were injected with the drug(s) or vehicle and placed on one side of a place preference apparatus. On the next day, animals initially injected with drug received vehicle (and vice versa) and placed on the other side of the chamber. This cycle was repeated four times. Animals were then tested for their compartment preference. In Experiment 2, subjects were treated identically except that 1.5 g/kg alcohol was administered. In both experiments, Group C displayed a significant preference for the drug-paired compartment. Group A (in both experiments) showed no conditioned effect. In Experiment 1, Group C/A failed to display a significant preference, spending an amount of time in each compartment that was the numerical average of Groups C and A. In Experiment 2, the cocaine-induced preference was completely abated by 1.5 g/kg alcohol. These results indicate that alcohol produces a dose-dependent modulation of the affective properties of cocaine.

Functional Imaging for the Monitoring of Clinical Outcomes of Pharmacotherapy

Functional and anatomic imaging have been used almost exclusively for diagnostic purposes. Because pharmacotherapy is expected to alter organ function, functional imaging is ideally suited to assess drug effects. The application of functional imaging techniques for this purpose has recently emerged. This paper reviews application of radiopharmaceuticals and nuclear imaging techniques to the assessment of pharmacologic effects in neurology, psychiatry, cardiology, and oncology.

[(11)]Cocaine: PET studies of cocaine pharmacokinetics, dopamine transporter availability and dopamine transporter occupancy

Cocaine was initially labeled with carbon-11 in order to track the distribution and pharmacokinetics of this powerful stimulant and drug of abuse in the human brain and body. It was soon discovered that [(11)C]cocaine was not only useful for measuring cocaine pharmacokinetics and its relationship to behavior but that it is also a sensitive radiotracer for dopamine transporter (DAT) availability. Measures of DAT availability were facilitated by the development of a graphical analysis method (Logan Plot) for reversible systems which streamlined kinetic analysis. This expanded the applications of [(11)C]cocaine to studies of DAT availability in the human brain and allowed the first comparative measures of the degree of DAT occupancy by cocaine and another stimulant drug methylphenidate. This article will summarize preclinical and clinical research with [(11)C]cocaine.

PET imaging studies in drug abuse

In spite of the massive public health problem associated with drug abuse, effective treatments remain elusive. This is due in part to a relatively poor understanding of the neurochemical changes which drugs of abuse produce in the human brain and the relationship of these changes to the behavioral and addictive properties of drugs. With the development of modern imaging methods and a variety of labeled drugs and radiotracers, it has now become possible to track many aspects of drug pharmacokinetics and pharmacodynamics directly in the human brain and to relate these parameters to the behavioral and toxic properties of drugs.

REVIEW

In this article, we will highlight some examples of the use of Positron Emission Tomography to measure drug pharmacokinetics and pharmacodynamics and their relationship to addiction and to toxicity.

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.

The interaction of dopamine, cocaine, and cocaethylene with ethanol on central nervous system depression in mice

The interactions between dopamine, cocaine, cocaethylene, and ethanol were studied in Swiss-Webster mice. The loss of the righting reflex (LORR) was used as a measure of CNS depression. Animals were injected intraperitoneally (IP) with ethanol (4.0 g/kg). which caused a LORR. Immediately upon regaining of the righting reflex, mice were injected intracerebroventricularly (ICV) with saline, dopamine (0.1, 0.5, or 1.0 mumol/kg), cocaine (1, 15, or 25 mumol/kg), or cocaethylene (1, 15, or 25 mumol/kg). In the presence of systemic ethanol, all three compounds produced CNS depression in a dose-dependent manner. The dopamine D2-receptor antagonist sulpiride and the D1-receptor antagonist fluphenazine were given acutely ICV with dopamine in the presence of systemic ethanol to examine whether these antagonists could block the return to the LORR produced by dopamine. Sulpiride, however, actually enhanced the interaction between ethanol and dopamine in a dose-dependent manner as measured by the LORR; fluphenazine neither blocked nor enhanced the effect of dopamine in the presence of systemic ethanol. In addition, these antagonists had no effect on cocaine- and cocaethylene-induced CNS depression in the presence of systemic ethanol. The results of this study showed that the neurotransmitter dopamine and both cocaine and cocaethylene can promote further CNS depression in the presence of systemic ethanol, and that dopamine was significantly more potent than cocaine and cocaethylene as measured by the return to the LORR.

Individual and combined effects of ethanol and cocaine on intracellular signals and gene expression

1. Ethanol and cocaine are drugs of abuse that can produce long-lived changes in behavior, including dependence. 2. A common set of neural pathways appears to mediate the addictive actions of ethanol and cocaine. 3. Many prominent aspects of drug dependence may be the result of alterations in intracellular signals as well as specific patterns of gene expression. 4. For instance, changes in G proteins and cAMP, phosphorylation of proteins and induction of c-fos and zif/268 in specific drug-sensitive brain regions may represent adaptive changes in response to a drug-dependent state. 5. The concurrent use of ethanol and cocaine is the most prevalent pattern of drug abuse in humans. However, the number of studies investigating the behavioral and molecular effects of this combination are few. 6. Emerging evidence indicates a possible antagonistic effect of ethanol and cocaine action on transcription factor function. In addition, cocaethylene (a psychoactive metabolite derived from combined ethanol and cocaine exposure) has significant effects on gene expression as well.

The lethal effects of ethanol and cocaine and their combination in mice: implications for cocaethylene formation

The HS line of mice was used to determine the LD50 values for cocaine and ethanol, as well as for cocaethylene, the enzymatic product of their coadministration. The LD50 of cocaethylene was found to be significantly lower than that of cocaine, and both were more potent in their lethality than ethanol. When a low-lethality dose of cocaine was administered with a nonlethal dose of ethanol, the result was a significant increase in the prevalence of lethality. Thus, the lethal effects of the dose of cocaine used were increased by the dose of ethanol administered such that the two drugs in combination were equipotent to cocaethylene. The results are discussed in light of the ability of the liver, via transestification, to rapidly form cocaethylene from cocaine in addition to ethanol's ability to decrease the catabolism of cocaine. Thus, the possibility exists that the increased lethality observed is produced by both the production of the more lethal cocaethylene and sustained levels of cocaine.

Premorbid behaviors produced by cocaine, ethanol and cocaethylene in the mouse

1. The premorbid behaviors produced by the administration of cocaine, ethanol, their combination, as well as a metabolite produced by their co-administration, viz. cocaethylene, were defined, determined and quantified in the HS strain of mice. 2. The LD50 for ethanol was 9.71 g/kg in males and 9.45 g/kg in females, whereas the LD50 values in male and female mice for cocaine were 101.55 and 90.00 mg/kg, respectively. 3. The data indicate that clonic-tonic seizures continued into status epilepticus after cocaine administration and prior to cocaine-induced lethality. In contrast, administration of the cocaine-ethanol metabolite cocaethylene produced status epilepticus without producing clonic-tonic seizures yet still resulted in lethality. 4. Thus, both cocaine and cocaethylene may produce their lethal effects in mice through neuro-regulatory mechanisms mediating protracted seizure induction.

Acute administration of alcohol blocks cocaine-induced striatal c-fos immunoreactivity protein in the rat

Immediate-early genes, such as c-fos, are induced in the brain by cocaine and other psychotropic drugs. This induction is thought to be mediated via the activation of dopamine D1 and glutamate N-methyl-D-aspartate (NMDA) receptor subtypes. Because alcohol selectively blocks NMDA receptor function, we determined the ability of alcohol to block the expression of c-fos normally induced by systemic cocaine exposure in perikarya of the rat striatum. Acute administration of alcohol (2 g/kg; IP) approximately 30 min prior to a single cocaine (20 mg/kg) injection significantly reduced the patchy appearance of intensely immunoreactive gene signal in dorsal-central quadrants of the caudate putamen. Separate administration of three doses of alcohol alone (1, 2, or 3 g/kg) was ineffectual in inducing FOS-like protein in this or other regions of the rat brain. The blockade of the encoded protein by alcohol was partial in magnitude reminiscent of that produced by MK-801 and related NMDA receptor antagonist drugs. Furthermore, the blockade of cocaine-induced FOS-like protein by alcohol occurred at a dose which produced a blood alcohol concentration of approximately 180 mg/dl (40 mM), comparable to that detected in intoxicating humans. Considering the fact that the concomitant use of alcohol and cocaine is the most common substance abuse pattern found in the addictive population, the present results suggest an antagonist effect exerted by these two drugs at the transcriptional level and further support the consensus that NMDA receptors are the plausible surface-target elements mediating some of the effects of alcohol and cocaine.

Comparative PET studies of the kinetics and distribution of cocaine and cocaethylene in baboon brain

Recent studies have suggested that cocaethylene, an active metabolite of cocaine found in blood and postmortem brain of individuals self-administering cocaine and alcohol, may play a role in the increased toxicity seen when coadministering these 2 drugs. We have used positron emission tomography (PET) and carbon-11 (t1/2:20.4 min) labeled cocaine and cocaethylene to compare the short-term kinetics of cocaine and cocaethylene in baboon brain. The regional uptake of [11C]cocaine cocaethylene in baboon brain. The regional uptake of [11C]cocaine ([11C]COC) and [11C]cocaethylene ([11C]CE), 5-8 mCi and 4-6 micrograms, in baboon brain (n = 7) were similar but clearance from whole brain (global, GL) and from striatum (SR), thalamus (TH), and cerebellum (CB) was slower for cocaethylene. Steady-state distribution volumes (DV) were not significantly different in the striatum but were greater for cocaethylene in the thalamus, cerebellum, and whole brain. Debenzoylation of cocaethylene proceeded at about one-third the rate of cocaine, as determined by in vitro incubation of labeled cocaethylene and labeled cocaine with baboon plasma and with purified horse butyryl-cholinesterase (EC 3.1.1.8). Even though the slower clearance of cocaethylene could lead to longer tissue exposures and potentially accentuated or different physiological effects relative to cocaine, the difference between the 2 drugs is not large. Thus it is more likely that the direct actions of cocaine and alcohol on some organs, rather than cocaethylene, account for this enhanced toxicity.