Neuropharmacological and clinical aspects of alcohol withdrawal

Pregabalin for the Treatment of Drug and Alcohol Withdrawal Symptoms: A Comprehensive Review

Treatments for physical dependence and associated withdrawal symptoms following the abrupt discontinuation of prescription drugs (such as opioids and benzodiazepines), nicotine, alcohol, and cannabinoids are available, but there is still a need for new and more effective therapies. This review examines evidence supporting the potential use of pregabalin, an α2δ voltage-gated calcium channel subunit ligand, for the treatment of physical dependence and associated withdrawal symptoms. A literature search of the MEDLINE and Cochrane Library databases up to and including 11 December 2015 was conducted. The search term used was '(dependence OR withdrawal) AND pregabalin'. No other date limits were set and no language restrictions were applied. Works cited in identified articles were cross-referenced and personal archives of references also searched. Articles were included based on the expert opinions of the authors. There is limited evidence supporting the role of pregabalin for the treatment of physical dependence and accompanying withdrawal symptoms associated with opioids, benzodiazepines, nicotine, cannabinoids, and alcohol, although data from randomized controlled studies are sparse. However, the current evidence is promising and provides a platform for future studies, including appropriate randomized, placebo- and/or comparator-controlled studies, to further explore the efficacy and safety of pregabalin for the treatment of withdrawal symptoms. Given the potential for pregabalin misuse or abuse, particularly in individuals with a previous history of substance abuse, clinicians should exercise caution when using pregabalin in this patient population.

Dexmedetomidine alleviates ethanol withdrawal symptoms in the rat

The effect of dexmedetomidine, a selective alpha 2-adrenoceptor agonist, on ethanol withdrawal symptoms was studied in chronically ethanol-fed rats. After a 4-day ethanol intoxication period the rats were given s.c. injections of dexmedetomidine (3, 10, or 30 micrograms/kg) or saline (control group) at 10, 16, 22, and 39 h after the last dose of ethanol. The severity of ethanol withdrawal symptoms (rigidity, tremor, irritability, hypoactivity) was rated up to 58 h, blind to the treatments. The results showed that dexmedetomidine at doses 10 and 30 micrograms/kg significantly diminished the severity of the ethanol withdrawal reaction as measured by the sum score of the three most specific withdrawal signs (rigidity, tremor, and irritability). Dexmedetomidine at 10 micrograms/kg was the most effective dose, especially in the latter half of the withdrawal period (23-58 h after last dose of ethanol). The results suggest that dexmedetomidine in the treatment of ethanol withdrawal symptoms should be further studied.

Functional characterization of a kindling-like model of ethanol withdrawal in cortical cultured neurons after chronic intermittent ethanol exposure

Chronic ethanol exposure has been reported to alter NMDA and GABA(A) receptor function and gene expression in brain regions of animals and mammalian cultured cortical neurons. In the present study, we investigated the effects of another model of chronic, but intermittent, ethanol treatment (CIE) on GABA(A) and NMDA receptor systems in cortical neurons. CIE (50 mM ethanol, 12 h exposure/12 h withdrawal, 5 cycles) exposure produced increased [3H]MK-801 binding and diazepam insensitive binding sites as measured by [3H]Ro15-4513 binding to cortical cultured neuronal membranes, at 0 h following the last treatment cycle relative to control neurons. The NMDA mediated increase in intracellular calcium [Ca2+]i was also increased following similar CIE treatment. CIE treatment also increased the ability of pentylenetetrazol (PTZ) to inhibit GABA mediated 36Cl- influx relative to control neurons. These effects were not reversible following 1 week ethanol withdrawal, implying enhanced sensitivity of PTZ to inhibit GABA(A) receptor mediated inhibition, and an increased NMDA receptor function in CIE treated cortical neurons. These alterations are consistent with the behavioral studies in animals, and suggest that both GABA(A) and NMDA receptors play an important role in ethanol withdrawal following either chronic or CIE exposure. Furthermore, this provides a feasible in vitro model for further biochemical and molecular studies of the mechanism underlying the CIE induced kindling-like phenomenon observed in humans.

Glutamate and benzodiazepine receptor autoradiography in rat brain after repetition of alcohol dependence

During repeated alcohol withdrawal, convulsive withdrawal behavior has been shown to be increased in a kindling-like manner in both clinical and experimental studies. In the present experiment, quantitative autoradiography was used to investigate binding of tritiated ligands to glutamate receptor subtypes and the benzodiazepine/GABA (BZ/GABA) receptor complex in rats exposed to 14 episodes of alcohol withdrawal. Seizures were detected in 25% of the animals during withdrawal episode 10-13. Repeated alcohol withdrawal resulted in a decrease in the number of [3H]-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid ([3H]-AMPA) binding sites in striatum and sub-regions of the entorhinal cortex, the cerebellum and the hippocampus, while the [3H]-flunitrazepam binding was down-regulated in the frontal cortex. There was no differences between the controls and the multiple withdrawal animals regarding the [3H]-dizocilpine ([3H]-MK801) binding and the [3H]-kainic acid binding. However, within the latter group, those animals in which withdrawal seizures were observed had increased [3H]-MK801 binding sites in focal regions of entorhinal cortex and hippocampus, compared to those in which seizures were not observed. The decreased AMPA binding suggested impaired glutamate neurotransmission. As such, this receptor probably did not contribute to alcohol withdrawal kindling, but rather was involved in seizure protective mechanisms during this process.

Metabolic mapping of the effects of chronic voluntary ethanol consumption in rats

The 2-[14C]deoxyglucose method was used to examine the effects of chronic, voluntary ethanol consumption on rates of local cerebral glucose utilization (LCGU). LCGU was measured in male Long-Evans rats immediately following the completion of a 60-min schedule-induced polydipsia drinking session. Three groups of animals were examined: animals with a history of ethanol consumption that received ethanol on the test day (ethanol-ethanol), animals with a similar ethanol history that were presented with water on the test day (ethanol-water), and a control group that received water throughout the experiment (water-water). Ethanol consumption on the test day resulted in a highly discrete pattern of metabolic changes, with significant decreases in glucose utilization in the hippocampal complex, habenula, anterior ventral thalamus, and mammillary bodies, whereas increases were observed in the nucleus accumbens and locus coeruleus. Rates of LCGU in the ethanol-water group were increased throughout all regions of the central nervous system examined, indicating that the long-term consumption of moderate ethanol doses that do not produce physical dependence can cause significant changes in functional brain activity.

Concurrent cocaine withdrawal is associated with reduced severity of alcohol withdrawal

The purpose of this study was to implement an empirical assessment of the clinical response to standard alcohol detoxification during withdrawal from both alcohol and cocaine. One hundred forty-nine males consecutively admitted in acute alcohol withdrawal to a hospital-based detoxification unit were studied. All subjects completed a 4-day chlordiazepoxide detoxification. Patients who used drugs other than cocaine were excluded. Fifty-five subjects withdrawing only from alcohol and 94 subjects withdrawing from both alcohol and cocaine, as evidenced by positive urinalysis and history, were studied. Both groups reported similar amounts of daily alcohol intake and had a similar age of onset of alcohol dependence. Parental alcoholism was equally frequent in both groups. Statistically, several variables were directly related to severity of alcohol withdrawal, including associated cocaine abuse, age, abnormal laboratory values, and duration of homelessness. As measured by the Alcohol Withdrawal Scale (AWS), alcohol withdrawal was less severe among cocaine users, not only at intake but throughout the 4-day detoxification. Singly addicted alcoholics were older and had longer drinking histories, more prior detoxifications, and more abnormal laboratory values than cocaine users. A multiple regression analysis demonstrated a significant relationship between cocaine and severity of alcohol withdrawal. Cocaine users more frequently requested reductions in chlordiazepoxide dosages than singly addicted alcoholics, complaining of dysphoria, sedation, and weakness. The severity of alcohol withdrawal was associated with recent cocaine use, age, laboratory abnormalities, and duration of homelessness. Concurrent cocaine withdrawal in the sample was associated with reduced severity of alcohol withdrawal. Possible neurobiological mechanisms, as well as study limitations affecting interpretation of the findings, are discussed. Tailored detoxification as opposed to standard detoxification regimens may be more appropriate for the clinical management of combined alcohol-cocaine withdrawal.

Ethanol withdrawal is associated with increased extracellular glutamate in the rat striatum

Extracellular glutamate was measured by microdialysis in the striatum of ethanol-dependent, freely behaving rats following withdrawal from chronic ethanol treatment. Within 12 h from withdrawal, extracellular glutamate rose to 255% of that in control, chronic sucrose-treated rats. Glutamate output remained elevated for the subsequent 12 h and returned to control levels within 36 h from the interruption of the treatment. The changes in glutamate were time-locked to the overt physical signs of withdrawal. In 12-h ethanol-withdrawn rats an ethanol challenge suppressed the withdrawal signs and reduced the extracellular glutamate. The NMDA receptor antagonist, dizocilpine, reduced both the physical signs of withdrawal and glutamate output. In contrast, diazepam reduced the withdrawal signs but failed to change the glutamate levels. These findings suggest that the increased extraneuronal glutamate reflects overactivity of excitatory neurotransmission during withdrawal. Furthermore, they provide a biochemical rationale for the use of NMDA receptor antagonists and ethanol itself in the treatment of ethanol withdrawal syndrome.

Prevention of ethanol-induced sympathetic overactivity and degeneration by dexmedetomidine

The effects of dexmedetomidine, a selective alpha 2-adrenoceptor agonist, on rat sympathetic neurons were studied during a 12-day, heavy ethanol exposure. Adult male Wistar rats were given ethanol or isocaloric sucrose three times a day by intragastric intubation. Both acute (a single dose of 300 micrograms/kg p.o.) and chronic (100 micrograms/kg x 2 P.O. throughout the experiment) effects of dexmedetomidine were tested. The superior cervical ganglia (SCG) of the ethanol-exposed, non-dexmedetomidine-treated rats showed an abnormally high overall level of tyrosine hydroxylase immunoreactivity (TH-IR) and catecholamine histofluorescence. However, a subpopulation of neurons had apparently lost their catecholamine synthetic activity, as they exhibited no TH-IR or catecholamine fluorescence. The ethanol-exposed ganglia also showed structural alterations (e.g., decreased neuronal size and increased occurrence of vacuolated neurons). In the ethanol-exposed, chronically dexmedetomidine-treated group, by contrast, the SCG exhibited TH-IR and catecholamine fluorescence intensities comparable to those seen in the control ganglia. All the structural parameters studied, as well, were at the control level in the chronically dexmedetomidine-treated group. The single dose of dexmedetomidine offered only marginal protection against the ethanol-induced alterations. These results suggest that chronic dexmedetomidine treatment may prevent ethanol-induced overactivity and degeneration of catecholaminergic neurons.

Chronic ethanol treatment upregulates the NMDA receptor function and binding in mammalian cortical neurons

In the present study, we investigated the effects of chronic ethanol exposure on NMDA-mediated increase in intracellular calcium concentration ([Ca2+]i) by means of fluorescent measurement of [Ca2+]i with Fura-2AM in mammalian cortical cultured neurons, and the radioligand [3H]MK-801 binding to cortical neuronal membranes. Chronic exposure of the cortical neurons to ethanol (50 mM, 5 days) did not produce any change in the cell protein, morphological appearance, and the resting [Ca2+]i; however, it significantly enhanced the NMDA-mediated increase in [Ca2+]i. The EC50 value of NMDA was not significantly altered following chronic ethanol exposure, however, its Emax value was increased by approximately 45%. Furthermore, chronic ethanol exposure increased the specific [3H]MK-801 binding in cortical neuronal membrane preparation by approximately 30%. The enhancement of the NMDA-mediated increase in [Ca2+]i and the increase in [3H]MK-801 specific binding were reversed following 48 h ethanol withdrawal. Additionally, this enhanced NMDA response and the increased [3H]MK-801 specific binding were susceptible to blockade by the concomitant chronic exposure of the cortical neurons to the NMDA receptor competitive (20 microM CPP), and non-competitive (1 microM MK-801) antagonists, but not by the non-NMDA receptor antagonist, CNQX (10 microM), and the L-type calcium channel blocker, nitrendipine (10 microM). Taken together, these results suggest that chronic ethanol exposure upregulated the NMDA receptor function and binding in cortical cultured neurons, and this increased NMDA receptor function is a NMDA receptor-mediated process. This altered NMDA receptor function may be responsible for the chronic ethanol-induced behavioral consequences and withdrawal syndrome associated with chronic ethanol exposure.

Corticosterone increases severity of acute withdrawal from ethanol, pentobarbital, and diazepam in mice

It has been suggested that withdrawal from several subclasses of central nervous system (CNS) depressants involves common underlying mechanisms. For example, mice genetically selected for severe ethanol withdrawal convulsions (Withdrawal Seizure Prone or WSP) have also been found to express severe withdrawal following treatment with barbiturates and benzodiazepines. Corticosteroids appear to modulate severity of withdrawal from CNS depressants. Therefore, it was hypothesized that corticosterone would enhance withdrawal convulsions following acute ethanol, pentobarbital, and diazepam in WSP mice. Corticosterone (20 mg/kg) administered following each of these drugs significantly increased severity of handling-induced convulsions during withdrawal. Corticosterone did not affect pre-withdrawal convulsion scores or handling-induced convulsions of drug-naive mice. These results suggest that withdrawal convulsions following acute ethanol, pentobarbital, and diazepam are sensitive to modulation by corticosterone and they support the hypothesis that stress may increase drug withdrawal severity.

Chronic ethanol intoxication induces differential effects on GABAA and NMDA receptor function in the rat brain

The effect of long-term treatment with ethanol was investigated on the function of gamma-aminobutyric acid A (GABAA) and N-methyl-d-aspartic acid (NMDA) receptors. Rats were rendered ethanol-dependent by repeated forced administration of a 20% ethanol solution (12 to 18 g/kg/day po) for 6 days and tested while still intoxicated or at different time intervals after withdrawal. t-[35S]Butylbicyclophosphorothionate (35S-TBPS) binding was increased by 30% in cortical homogenates of rats killed 1 to 3 hr after last ethanol administration, when compared with saline-treated animals. However, GABA-stimulated 36Cl- uptake and its enhancement by flunitrazepam was decreased in the ethanol-treated animals. 35S-TBPS binding and 36Cl- influx measured 9 to 24 hr following the last ethanol injection, when withdrawal signs were present, were unmodified with respect to saline-treated rats. Moreover, the effects of both isoniazid and FG 7142 on 35S-TBPS binding were unchanged in ethanol-dependent rats tested at 1 to 3 and 9 to 24 hr, compared with controls. In contrast, ethanol-withdrawn rats tested at 9 to 24 hr showed a dramatic enhancement in their sensitivity to the convulsant action of isoniazid (50 to 250 mg/kg, sc). The same animals were also more susceptible to the convulsant action of NMDA (0.5 to 5 micrograms/5 microliters/rat intracerebroventricularly) and kainic acid (12 mg/kg, ip), and this effect was paralleled by an enhancement (+25%) in the density of 3H-MK 801 recognition sites in the hippocampus.(ABSTRACT TRUNCATED AT 250 WORDS)

Seizure threshold to lidocaine is decreased following repeated ECS (electroconvulsive shock)

Seizure susceptibility to lidocaine was investigated in rats which had received repeated ECS (electroconvulsive shock). In the first experiment three groups of rats received an ECS daily for 18 days, an ECS weekly for 18 weeks, and 18 sham treatments, respectively. Twelve weeks after the last ECS all rats received a lidocaine challenge (LC) in the form of an intraperitoneal (IP) injection of lidocaine (65 mg/kg). After the injection the animals were observed for occurrence of motor seizures. A total of 67% (10/15), 47% (7/15), and 0% (0/18) of the daily, weekly, and sham groups, respectively, had motor seizures in response to the LC. In the second experiment five groups of rats received an ECS daily for 0, 1, 6, 18, and 36 days, respectively. Eighteen weeks after the last ECS all rats received an LC and 0% (0/15), 13% (2/15), 20% (3/15), 53% (8/15), and 58% (7/12), respectively, developed seizures in response to the LC. In the third experiment two groups of rats received daily ECS and sham-ECS, respectively. Twenty-four hours after the last ECS all rats received an LC. A total of 60% (9/15) of the ECS group and 0% (0/10) of the sham-ECS group had seizures in response to the LC.(ABSTRACT TRUNCATED AT 250 WORDS)