Acute cocaine toxicity: the effect of agents in non-seizure-induced death

Preventative effects of aripiprazole and quetiapine on seizure and lethality in a mice cocaine toxicity model: an experimental study

Objective

To assess the effectiveness of pre-treatment with aripiprazole and quetiapine to prevent acute cocaine toxicity in a mouse model of cocaine toxicity.

Methods

This experimental study included three groups (n = 25 per group) of mice that were intraperitoneally injected with normal saline solution, 10 mg/kg quetiapine or 10 mg/kg aripiprazole 15 min before 105 mg/kg cocaine hydrochloride. When the cocaine administration was completed, researchers blinded to the study groups observed the mice in terms of seizures and death for a further 30 min.

Results

In the cocaine + quetiapine group, the mean ± SE time to the first seizure was 10.80 ± 2.27 min and seizure activity was detected in 18 mice (72%) by the end of the 30 min. In the cocaine + aripiprazole group, the mean ± SE time to the first seizure was 18.10 ± 1.94 min and seizure activity was detected in 15 mice (60%) by the end of the 30 min. When compared with the control group, there was a significant difference between the cocaine + quetiapine and cocaine + aripiprazole groups in terms of seizure activity. Survival time was increased in the cocaine + aripiprazole group compared with the control and cocaine + quetiapine groups.

Conclusion

Quetiapine and aripiprazole pre-treatment reduced seizure activity and delayed the onset of seizures compared with the control group.

Protective effects of minocycline, doxycycline and tetracycline on seizure and lethality in a mice cocaine toxicity model

INTRODUCTION

Acute cocaine intoxication is one of the important causes of admission to emergency department, especially in western countries. We aimed to compare the efficacies of tetracycline, minocycline, doxycycline in the prevention of seizures and deaths in mice due to cocaine intoxication.

METHODS

In the study, a total of 120 balb-c male mice weighing 25-30 g were randomized into 4 groups as tetracycline 255 mg/kg, minocycline 170 mg/kg, doxycycline 157 mg/kg, 0.5 ml saline (placebo). The doses of tetracycline, minocycline and doxycycline are the calculated ED50 values. The mice in the groups received 93 mg/kg cocaine intraperitoneally 10 min after drug administration. The dose of cocaine is 50% of the lethal dose. After cocaine injection, all mice were observed for 30 min in terms of cocaine toxicity findings. Mortality rates, death times, seizure activities, and seizure onset times of the mice were clinically evaluated in an observational way.

RESULTS

There were significant differences among all the groups in terms of seizure and lethality (p < 0.001). The ratio of animals with seizures was significantly lower in the minocycline (73.3%), and doxycycline (73.3%) groups (all p = 0.040). The ratio of animals with lethality was significantly lower in the minocycline (23.3%) group compared with vehicle (p < 0.001).

CONCLUSION

In our acute cocaine intoxication model, minocycline was effective in terms of lethality and preventing seizures, doxycycline was effective in preventing seizures.

Clinical Potential of an Enzyme-based Novel Therapy for Cocaine Overdose

It is a grand challenge to develop a truly effective medication for treatment of cocaine overdose. The current available, practical emergence treatment for cocaine overdose includes administration of a benzodiazepine anticonvulsant agent (e.g. diazepam) and/or physical cooling with an aim to relieve the symptoms. The inherent difficulties of antagonizing physiological effects of drugs in the central nervous system have led to exploring protein-based pharmacokinetic approaches using biologics like vaccines, monoclonal antibodies, and enzymes. However, none of the pharmacokinetic agents has demonstrated convincing preclinical evidence of clinical potential for drug overdose treatment without a question mark on the timing used in the animal models. Here we report the use of animal models, including locomotor activity, protection, and rescue experiments in rats, of drug toxicity treatment with clinically relevant timing for the first time. It has been demonstrated that an efficient cocaine-metabolizing enzyme developed in our previous studies can rapidly reverse the cocaine toxicity whenever the enzyme is given to a living rat, demonstrating promising clinical potential of an enzyme-based novel therapy for cocaine overdose as a successful example in comparison with the commonly used diazepam.

Assessment of propofol, midazolam and ziprasidone, or the combinations for the prevention of acute cocaine toxicity in a mouse model

STUDY OBJECTIVE

To evaluate the effects of pretreatment, midazolam (M), propofol (P), ziprasidone (Z), and two combinations of [(midazolam plus propofol (MP); midazolam plus ziprasidone (MZ)] in mice models in the prevention of seizures, and death due to acute cocaine toxicity.

METHODS

180 male CF-1 mice were randomized to 6 groups (30/group) in this experimental study. The animals were administered intraperitoneal injections of M (2mg/kg), P (25mg/kg), Z (4mg/kg), MP (2mg/kg and 25mg/kg) and MZ (2mg/kg and 4mg/kg) or saline (S) as a pretreatment. 10min later, the mice were administered intraperitoneal injections of 105mg/kg cocaine. The groups were observed for cocaine-induced seizure and lethality.

RESULTS

The MP and MZ combinations showed the highest protective effect in terms of seizure and lethality relative to P and S (p<0.001). M and Z were found effective compared to P and S (p<0.001). There were no significant differences among MP and MZ, however there were significant differences between MP and Z in terms of lethality (p=0.05). There were no significant differences among MP, MZ, M and Z groups in terms of seizure (p>0.05). No death was observed in the MP combination group. Seizure rate was observed o be least in the MZ group with respect to the other groups.

CONCLUSION

According to our particular mouse model, this study suggests that MP and MZ combinations may be more effective than M or Z only for the prevention of cocaine-induced seizure and lethality. However, P alone does not prevent cocaine-induced seizure and lethality.

Benzodiazepines and antipsychotic medications for treatment of acute cocaine toxicity in animal models – A systematic review and meta-analysis

There are no controlled human studies to determine the efficacy of benzodiazepines or antipsychotic medications for prevention or treatment of acute cocaine toxicity. The only available controlled data are from animal models and these studies have reported inconsistent benefits. The objective of this study was to quantify the reported efficacy of benzodiazepines and antipsychotic medication for the prevention of mortality due to cocaine poisoning. We conducted a systematic review to identify English language articles describing experiments that compared a benzodiazepine or antipsychotic medication to placebo for the prevention of acute cocaine toxicity in an animal model. We then used these articles in a meta-analysis with a random-effects model to quantify the absolute risk reduction observed in these experiments. We found 10 articles evaluating antipsychotic medications and 15 articles evaluating benzodiazepines. Antipsychotic medications reduced the risk of death by 27% (95% CI, 15.2%–38.7%) compared to placebo and benzodiazepines reduced the risk of death by 52% (42.8%–60.7%) compared to placebo. Both treatments showed evidence of a dose-response effect, and no experiment found a statistically significant increase in risk of death. We conclude that both benzodiazepines and antipsychotic medications are effective for the prevention of lethality from cocaine toxicity in animal models.

Pretreatment with group I metabotropic glutamate receptors antagonists attenuates lethality induced by acute cocaine overdose and expression of sensitization to hyperlocomotor effect of cocaine in mice

Cocaine abuse and dependence is a worldwide health problem. However, there are no currently approved medications to reduce cocaine abuse/relapse and toxicity. The aim of the present study was to test, whether group I metabotropic glutamate receptors (mGluRs) antagonists (mGluR1 and mGluR5) differentially regulate toxic versus behavioral effects of cocaine, both phenomena relevant to the psychopathology of cocaine addiction in humans. In the present study, we assessed the impact of mGluR1 antagonist-EMQMCM and mGluR5 antagonist-MTEP on the cocaine-induced lethality and the expression of sensitization to hyperlocomotor effect of cocaine in mice. Our study indicated that EMQMCM and MTEP, both substances at the doses of 5 and 10 mg/kg (but not 2.5 mg/kg), decreased cocaine-induced lethality produced by 75 mg/kg of cocaine, which was given acutely. The effect of EMQMCM was dose-dependent, and this compound at the dose of 10 mg/kg almost completely abolished the lethality induced by cocaine. MTEP reduced this cocaine effect at the doses of 5 and 10 mg/kg, equally. Furthermore, EMQMCM (1.25-5 mg/kg) at the doses of 2.5 and 5.0 mg/kg, and MTEP (2.5-10 mg/kg) only at the highest dose of 10 mg/kg, significantly reduced the expression of cocaine-induced (10 mg/kg) behavioral sensitization. Our results suggest that stimulation of mGluR1 and mGluR5 is involved in lethal effect of cocaine overdose and cocaine seeking behavior evaluated in behavioral sensitization test. However, the participation of mGluR1 in these cocaine effects seems to be dominant. Therefore, antagonists showing preferences towards mGluR1 might be useful in therapy of cocaine toxicity and abuse.

A bacterial cocaine esterase protects against cocaine-induced epileptogenic activity and lethality

STUDY OBJECTIVE

Cocaine toxicity results in cardiovascular complications, seizures, and death and accounts for approximately 20% of drug-related emergency department visits every year. Presently, there are no treatments to eliminate the toxic effects of cocaine. The present study hypothesizes that a bacterial cocaine esterase with high catalytic efficiency would provide rapid and robust protection from cocaine-induced convulsions, epileptogenic activity, and lethality.

METHODS

Cocaine-induced paroxysmal activity and convulsions were evaluated in rats surgically implanted with radiotelemetry devices (N=6 per treatment group). Cocaine esterase was administered 1 minute after a lethal dose of cocaine or after cocaine-induced convulsions to determine the ability of the enzyme to prevent or reverse, respectively, the effects of cocaine.

RESULTS

The cocaine esterase prevented all cocaine-induced electroencephalographic changes and lethality. This effect was specific for cocaine because the esterase did not prevent convulsions and death induced by a cocaine analog, (-)-2beta-carbomethoxy-3beta-phenyltropane. The esterase prevented lethality even after cocaine-induced convulsions occurred. In contrast, the short-acting benzodiazepine, midazolam, prevented cocaine-induced convulsions but not the lethal effects of cocaine.

CONCLUSION

The data showed that cocaine esterase successfully degraded circulating cocaine to prevent lethality and that cocaine-induced convulsions alone are not responsible for the lethal effects of cocaine in this model. Therefore, further investigation into the use of cocaine esterase for treating cocaine overdose and its toxic effects is warranted.

Ziprasidone, diazepam, or the combination for prevention of cocaine toxicity in a mouse model

BACKGROUND

Acute cocaine poisoning is a common problem in the United States. Sedation with benzodiazepines is the standard treatment, but animal studies have suggested that ziprasidone is also protective.

OBJECTIVES

To assess whether the combination of these two medications would offer more protection than either treatment alone.

METHODS

This was a randomized, blinded, placebo-controlled trial in CF-1 mice. The authors administered intraperitoneal injections of 2 mg/kg diazepam (group D), 4 mg/kg ziprasidone (group Z), the same dose of both drugs (group DZ), or saline 15 minutes before intraperitoneal administration of 105 mg/kg cocaine (an estimated lethal dose to 70%). The number of animals with seizures and apparent lethality over the following 30 minutes was recorded.

RESULTS

All treatments increased survival relative to placebo (relative risk: D = 2.6, Z = 2.3, DZ = 2.9) and decreased seizures (relative risk: D = 0.5, Z = 0.3, DZ = 0.02).

CONCLUSIONS

This study suggests that diazepam and ziprasidone have efficacy for preventing lethality from cocaine poisoning in an animal model but that the combination offers little addition to either therapy alone. However, the combination may be more effective for prevention of cocaine-induced seizures.

Comparison of effect of ethanol and anticonvulsants on cardiovascular drug-modified cocaine toxicity

The anticonvulsant (AC drug)- or ethanol (EtOH)-modified effects of cardiovascular (CV) drugs against cocaine (COCA)-induced toxicity were examined in male ICR mice. Nontoxic doses of the CV drugs nimodipine (NIMO), prazosin (PRA), phentolamine (PHEN), propranolol (PRO), and enalapril (ENA) were used with or without the AC drugs diazepam (DZP), phenobarbital (PHB), phenytoin (PHY), and EtOH. Each CV drug combined with or without each AC drug was administered intraperitoneally (IP) 5 min before an IP injection of COCA 75 mg/kg. Of the CV drugs examined, PRA 5 mg/kg and PHEN 5 mg/kg protected against COCA-induced seizures, but only the alpha1-adrenergic blocking agent PRA protected against COCA-induced deaths. Of the AC drugs examined, DZP 5 mg/kg and PHB 50 mg/kg, as well as EtOH 3 g/kg, attenuated the severity of the COCA-induced seizures, but only PHB protected against COCA-induced deaths. The total mortality rate was significantly, often synergistically, decreased compared to the COCA-only group when the appropriate CV drugs were combined with the AC drugs: PRA 5 mg/kg in the EtOH-cotreated groups, PRA 5 mg/kg, PHEN 5 mg/kg or ENA 10 mg/kg in the DZP-cotreated groups, and NIMO 5 mg/kg, PRA 5 mg/kg, PHEN 5 mg/kg, or PRO 10 mg/kg in the PHB-cotreated groups. The decrease in the COCA concentration in the blood and/or brain was not always accompanied by an attenuation of the mortality rate. However, the attenuation of severe seizures by a single PRA, PHEN, DZP, or PHB cotreatment was accompanied by a decrease in the brain COCA concentration.

Cocaine and lidocaine have additive inhibitory effects on the GABAA current of acutely dissociated hippocampal pyramidal neurons

Inhibition mediated by gamma-aminobutyric acid (GABA) is a major target for the central actions of cocaine and lidocaine, which can result in seizures, especially when these drugs are abused in combination. In the present study, we investigated how cocaine and lidocaine interact to depress GABA current (IGABA), recorded by the whole-cell technique in freshly isolated rat hippocampal neurons. Cocaine depressed IGABA in a concentration dependent manner, such that cocaine was more potent against lower than higher GABA concentrations: the cocaine IC50 was 0.13, 0.62 and 1.2 mM for GABA at 2, 10 and 100 microM, respectively. Cocaine depressed IGABA to the same extent in the absence and presence of 1 microM tetrodotoxin, indicating that cocaine inhibition of IGABA is distinct from its Na+ channel blocking action. Lidocaine reversibly depressed IGABA evoked by 10 microM GABA, with an IC50 of 9.8 mM. In the presence of 3 mM lidocaine, 0.3 mM cocaine depressed IGABA (10 microM GABA) to 30+/-7%. The significantly greater depression by the combined agents (p<0.05) indicates additive effects on the GABA receptor/channel complex, which are likely to contribute to the additive convulsant effects noted when these drugs are abused in combination.

Brain beta-endorphin immunoreactivity as an index of cocaine and combined cocaine-ethanol toxicities

The present study examines alterations in the cytoplasmic immunoreactivity of brain beta-endorphin, an endogenous opioid peptide regarded as the mediator of both euphoria and antinociceptive systems, in relation to toxicities due to cocaine and combined cocaine-ethanol. Beta-endorphin-immunoreactive cells were visualized and counted in adjacent sections from male rat brains at the level of the arcuate nucleus. In this region, cytoplasmic beta-endorphin immunoreactivity is prevalent. An intraperitoneal injection of cocaine (75 or 15 mg/kg) was given 15 min after an intraperitoneal injection of 3 g/kg ethanol or vehicle. With a fatally toxic dose (75 mg/kg) of cocaine, the number of neurons exhibiting cytoplasmic beta-endorphin immunoreactivity (immunoreactive nerve cells) was significantly increased immediately after the drug administration. Ethanol further enhanced the effects of both 15 and 75 mg/kg of cocaine. When the immunoreactivity was visually estimated by computer imaging analysis, lightly stained, weakly immunoreactive cells with photographic light absorption values greater than 50% were enhanced in the cocaine-ethanol groups compared to the cocaine only groups. Fatal toxicities were only observed in the groups treated with the high cocaine doses (75 mg/kg), with or without ethanol. In these groups, the number of strongly immunoreactive cells had increased significantly compared to the other groups. In the group treated with the high cocaine dose (75 mg/kg) plus ethanol, an increased frequency of late deaths that occurred over 1 h after the drug administration was observed, together with a decreased severity of cocaine-induced seizures and an early enhancement of weakly immunoreactive cells. Unlike the strongly immunoreactive cells, the weakly immunoreactive cells appeared to be continuously enhanced, based on an experiment examining beta-endorphin immunoreactivity at 24 h after an injection of 50 mg/kg cocaine.

Cocaine depresses GABAA current of hippocampal neurons

Although blockade of dopamine re-uptake and the resulting elevation of excitatory agonists is commonly thought the primary mechanism of cocaine-induced seizures, it is possible that other neurotransmitters such as gamma-aminobutyric acid (GABA) are involved. To examine this possibility, the effects of cocaine on the whole cell GABA current (IGABA) of freshly isolated rat hippocampal neurons were investigated with the patch-clamp technique. Preincubation or acute application of cocaine reversibly suppressed IGABA. The IC50 was 127 microM when cocaine was applied before the application of GABA. The concentration-response relations of cocaine in various GABA concentrations revealed that cocaine inhibited IGABA non-competitively. This effect of cocaine appeared to be independent of voltage. The present study suggests that the GABA receptor/channel complex is also a target for cocaine's action. The suppression of IGABA may contribute to cocaine-induced seizures.

Relation of cocaine use to seizures and epilepsy

PURPOSE

Cocaine can provoke seizures, exacerbate a preexisting seizure disorder, or cause an ischemic or hemorrhagic stroke that leads to seizures. To determine the importance of cocaine use in patients with and without epilepsy, we studied these relations and other risk factors for seizures and the mode of cocaine use.

METHODS

We reviewed all charts of emergency department visits and hospitalizations of patients with discharge diagnoses simultaneously listing seizures, epilepsy, and cocaine use during a 24-month period. Data collected included patient age, sex, route of cocaine use, seizure description and duration of epilepsy, provocative factors, results of electroencephalography and computed tomography, treatment, and outcome.

RESULTS

Of 67,668 adult emergency department visits and 25,768 adult admissions, 1,900 were cocaine related, and 58 of these also had seizures or epilepsy. Seizure occurrences were approximately equally distributed among groups with idiopathic epilepsy, remote symptomatic localization-related epilepsy, cerebrovascular disease, and acute symptomatic seizures due to cocaine use alone. Less frequently, seizures were cryptogenic or symptomatic of metabolic abnormalities.

CONCLUSIONS

Cocaine use can reduce seizure threshold in patients with underlying epilepsy as a direct toxic effect or indirectly by contributing to poor compliance with antiepileptic drug treatment, poor diet, or poor sleep habits. In 12 of the 58 patients, cocaine appeared to be the only provocative factor. This may be a less significant risk factor for epilepsy than either alcohol or head trauma.

Differential effects of NMDA receptor and dopamine receptor antagonists on cocaine toxicities

Cocaine produces not only euphoric effects but also a wide range of detrimental effects, including seizures and lethality. The present study examined the involvement of the N-methyl-D-aspartate (NMDA) subtype of the glutamate receptors and the dopamine D1 and D2 receptors in seizure activity and lethality observed following single and repeated injections of cocaine in ddY mice. Repeated injections of 60 mg/kg cocaine resulted in the development of sensitization to the convulsant effects of cocaine during an initial 3 or 4 days, followed by the development of tolerance at day 5 and day 6. Repeated injections of 90 mg/kg cocaine augmented the lethal effect of cocaine progressively over the course of treatment. Treatment with 0.1-0.4 mg/kg of the noncompetitive NMDA receptor antagonist, MK-801, prevented the development of sensitization to cocaine-induced seizures in a dose-dependent manner, and attenuated partially the cocaine-induced lethality. In contrast, treatment with 10-50 mg/kg of the dopmaine D2 receptor antagonist, sulpiride, had no effects on the development of sensitization and tolerance to cocaine-induced seizures. On the other hand, treatment with 0.1-0.5 mg/kg of the dopamine D1 receptor antagonist, SCH 23390, not only prolonged the latency to 90 mg/kg cocaine-induced seizures but also delayed the development of sensitization to the convulsant effects of cocaine. The increased lethality observed following repeated injection of cocaine was unaffected by treatment with SCH 23390, but was severely aggravated by treatment with sulpiride.(ABSTRACT TRUNCATED AT 250 WORDS)

Serotonergic mediation of cocaine seizures in mice

We used genetically heterogeneous HS mice to investigate the effects of drugs that alter brain concentrations of serotonin on cocaine-induced convulsions and lethality. The racemer of fenfluramine, which increases synaptic serotonin, was coadministered with a dose (60 mg/kg, intraperitoneally) of cocaine that does not produce status epilepticus or death. This drug combination significantly increased the occurrence and decreased the time of onset of status epilepticus, but did not affect lethality. Likewise, 2.5 mg/kg of the D-isomer, of fenfluramine increased the occurrence of status epilepticus. Neither isomer effected lethality. When 2.5 mg/kg cinanserin, a drug that antagonizes postsynaptic serotonergic receptors, was coadministered with a higher (95 mg/kg) dose of cocaine, the time of onset of status epilepticus was significantly increased, whereas lethality was reduced. The results are discussed in light of the action of cocaine upon serotonin neurons and the relationship between seizurogenic activity and cocaine-induced lethality.

Flumazenil induces seizures and death in mixed cocaine-diazepam intoxications

STUDY HYPOTHESIS

Administration of the benzodiazepine antagonist flumazenil may unmask seizures in mixed cocaine-benzodiazepine intoxication.

DESIGN

Male Sprague-Dawley rats received 100 mg/kg cocaine IP alone, 5 mg/kg diazepam alone, or a combination of diazepam and cocaine. Three minutes later, groups were challenged with vehicle or flumazenil 5 or 10 mg/kg IP. Animal behavior, seizures (time to and incidence), death (time to and incidence), and cortical EEG tracings were recorded.

INTERVENTIONS

Administration of flumazenil to animals after they had received a combination dose of cocaine and diazepam.

RESULTS

In group 1, animals received cocaine followed by vehicle. This resulted in 100% developing seizures and death. Group 2 received diazepam alone followed by vehicle. Animals became somnolent and none died. Group 3 received diazepam followed by 5 mg/kg flumazenil. Animals became somnolent after diazepam and then active after flumazenil administration. In group 4, a combination of cocaine and diazepam was administered simultaneously. This resulted in no overt or EEG-detectable seizures and a 50% incidence of death. Group 5 received a similar combination of cocaine and diazepam, followed later by 5 mg/kg flumazenil. This resulted in an increased incidence of seizures, 90% (P < .01), and death, 100% (P < or = .01), compared with group 4. Group 6 received cocaine and diazepam followed by 10 mg/kg flumazenil. This also resulted in an increased incidence of seizures, 90% (P < or = .01), and death, 90% (P < or = .05), compared with group 4.

CONCLUSION

Flumazenil can unmask seizures and increase the incidence of death in a model of combined cocaine-diazepam intoxications.