The biological basis of benzodiazepine dependence

Evaluation of safety and side effects in the process of anti-anxiety drug development *

As with other drugs it is necessary to look for changes induced by anxiolytics on vital signs, laboratory parameters and adverse events. In return, in a more specific way for anxiolytics, we will look at side effects at the central nervous system level with psychological and physiological battery tests. We will also assess the safety of use of anxiolytics in certain specific conditions, such as overdose or withdrawal and in certain populations such as the elderly, neonates and children. The assessment of safety and side effects, whatever the drug type studied, must come early in the developing process of a drug (phases I, II and III).

Neuroadaptive processes in GABAergic and glutamatergic systems in benzodiazepine dependence

Knowledge of the neural mechanisms underlying the development of benzodiazepine (BZ) dependence remains incomplete. The gamma-aminobutyric acid (GABA(A)) receptor, being the main locus of BZ action, has been the main focus to date in studies performed to elucidate the neuroadaptive processes underlying BZ tolerance and withdrawal in preclinical studies. Despite this intensive effort, however, no clear consensus has been reached on the exact contribution of neuroadaptive processes at the level of the GABA(A) receptor to the development of BZ tolerance and withdrawal. It is likely that changes at the level of this receptor are inadequate in themselves as an explanation of these neuroadaptive processes and that neuroadaptations in other receptor systems are important in the development of BZ dependence. In particular, it has been hypothesised that as part of compensatory mechanisms to diazepam-induced chronic enhancement of GABAergic inhibition, excitatory mechanisms (including the glutamatergic system) become more sensitive [Behav. Pharmacol. 6 (1995) 425], conceivably contributing to BZ tolerance development and/or expression of withdrawal symptoms on cessation of treatment, including increased anxiety and seizure activity. Glutamate is a key candidate for changes in excitatory transmission mechanisms and BZ dependence, (1) since there are defined neuroanatomical relationships between glutamatergic and GABAergic neurons in the CNS and (2) because of the pivotal role of glutamatergic neurotransmission in mediating many forms of synaptic plasticity in the CNS, such as long-term potentiation and kindling events. Thus, it is highly possible that glutamatergic processes are also involved in the neuroadaptive processes in drug dependence, which can conceivably be considered as a form of synaptic plasticity. This review provides an overview of studies investigating changes in the GABAergic and glutamatergic systems in the brain associated with BZ dependence, with particular attention to the possible differential involvement of N-methyl-D-aspartate and alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors in these processes.

Nightmares and panic disorder associated with carvedilol overdose

OBJECTIVE

To report a case of nightmares and sleep disorder associated with improper use of carvedilol, an alpha/beta-blocker, and to model the time course of receptor occupancy in this patient.

CASE SUMMARY

A 41-year-old man with panic disorder had been treated with alprazolam 1.2 mg/d (3 times daily), carvedilol 10 mg/d (once in the morning), and etizolam 0.5 mg (for anxiety attack). Although the physical and psychological symptoms gradually improved, he reported nightmares and panic attacks. An interview revealed that he had been taking carvedilol 5 mg twice a day after lunch and dinner on his own initiative, in addition to the prescribed dosage. The patient was asked to take carvedilol 10 mg only after breakfast, as had been advised. Consequently, the sleep disorder and nightmares disappeared.

METHODS

We calculated the time courses of beta(2)-adrenoceptor binding occupancy in the central nervous system after oral administration of carvedilol with the ordinary and improper regimens by using pharmacokinetic/pharmacodynamic parameters obtained from the literature.

RESULTS

Compared with the ordinary dose of carvedilol 10 mg once a day, the improper regimen (10 mg after breakfast followed by 5 mg after lunch and dinner) increases the beta(2)-adrenoceptor binding occupancy at night (2300) to as high as the mean beta(2)-adrenoceptor binding occupancy after an ordinary dose of propranolol.

CONCLUSIONS

The sleep disorder and nightmares experienced by this patient had been induced by elevation of central beta(2)-adrenoceptor binding occupancy at night as the result of improper use of carvedilol.

Experiences of long-term tranquillizer use: a psychodynamic perspective

The aim of the article is to analyse narrative descriptions and experiences of long-term tranquillizer use. The analysis is based on a Danish in-depth study of 50 informants with a self-diagnosed dependency on tranquillizers. The theoretical analysis is dependent on psychodynamic reasoning. Further, the psychodynamic perspective is integrated within a multi-dimensional model that considers biological, cognitive, identity, gender and social learning factors. The analysis reveals the possibility of achieving a detailed understanding of the dynamic processes involved in the development of long-term tranquillizer use. Important themes frequently mentioned in the clients' descriptions are traumatic childhood experiences, identity problems, life crises in adulthood and difficulties in stopping taking psychotropic drugs.

Identity, cognitive structure, and long-term tranquillizer use: a multidimensional approach

The article discusses different theoretical perspectives that are relevant in analysing long-term tranquillizer use. The theories mentioned are, e.g., behavioral theory models, cognitive models, humanistic and existential models, transpersonal identity models, psychodynamic reasoning, sociological and anthropological perspectives. A multidimensional model focusing on the connection between identity structure and long-term tranquillizer use is presented. The article argues for the use of mixed methodological strategies, e.g., quantitative and qualitative methods. The implications of the 'actor-spectator paradox" for the analysis of data are also discussed in some detail.

Toward an integrative approach in the analysis of dependency problems

This article takes some preliminary steps towards an integrated analysis of dependency problems e.g., long-term tranquillizer use, alcohol dependence, problematic use of narcotics. It argues for the need to outline important theoretical, epistemological, and methodological prerequisites in the analysis of the complex dynamic developmental processes involved in dependency problems. The dynamic process leading to dependence can be studied by the aid of an artificial science neural network approach in combination with a mixed method strategy including a clarification of a combination of different epistemological positions. It is intended that the empirical output of this complex strategy will provide a starting point for a new theoretical analysis which, in turn, will lead to new and more relevant input variables in the neural network approach that will help us to extend our knowledge of the dynamic processes leading to dependency.

Epilogue: drawing together the threads and perspectives on the long-term use of psychotropics

The aims of the epilogue are to draw together the threads in this issue by reviewing some themes presented in the previous chapters and to consider the relationship between the perspectives mentioned. The implications of a multidimensional perspective for future research, treatment and prevention are discussed. It is emphasized that the social sciences have an important part to play in helping us understand long-term use of psychotropics. The social sciences provide insights of importance for research, treatment and prevention of dependency on psychotropics, and also, may help us deal better with these kind of problems in the future.

GABA(A) receptor gene expression in rat cortex: differential effects of two chronic diazepam treatment regimes

Diazepam is widely prescribed as an anxiolytic but its therapeutic application is limited because with daily use tolerance develops to certain aspects of its pharmacological profile. We compared the effects of two dosing paradigms on GABA(A) receptor gene expression and benzodiazepine binding characteristics. Equivalent daily doses of 15 mg/kg/day diazepam were delivered either via constant infusion or daily subcutaneous injection for 14 days. The two distinct treatment regimes produced significantly different changes in GABA(A) receptor alpha4-, beta2-, beta3- and gamma1-subunit mRNA steady-state levels. Similar changes in the GABA enhancement of flunitrazepam binding and the BZ3/BZ2 subtype ratio determined ex vivo were produced, however, significant differences were found in [(3)H]-Ro 15-4513 binding between cortical tissue from diazepam injected animals compared with diazepam infused animals. Our data suggest that it is the diurnal fluctuations in receptor occupancy that are responsible for the different effects produced by these two dosing regimes.

Disturbed memory and amnesia related to intensive care

Patients, when admitted to an intensive care unit (ICU), have one thing in common: their illness is life-threatening. Patients may remain on ICU in a critical condition, needing support with their breathing, circulation, and/or kidneys for varying lengths of time, from days to weeks. During that time the patients will receive sedative and analgesic drugs to ensure compliance with artificial ventilation. Patients recovering from critical illness frequently have little or no recall of their period in ICU, or remember nightmare, hallucinations, or paranoid delusions. The nature, extent and reason for these difficulties, have been under-reported and consequently our purpose was to conduct a review of memory problems experienced by ICU patients. A systematic literature review of computer databases (Medline, PsycLit, and CINAHL) identified 25 relevant papers. In addition, other relevant articles were obtained, citation lists and associated articles retrieved. Due to lack of research on processes underlying memory problems in ICU patients all articles that introduced an insight into possible mechanisms were included in the review. There seem to be two possible processes contributing to memory problems in ICU patients. First the illness and treatment may have a general dampening effect on memory. Delirium and sleep disturbance are both common in ICU patients. Delirium can result in a profound amnesia for the period of confusion. Sleep deprivation exacerbates the confusional state. Slow wave sleep is important for the consolidation of episodic memories. Treatment administered to patients in ICU can have effects on memory. Opiates, benzodiazepines, sedative drugs such as propofol, adrenaline, and corticosteroids can all influence memory. In addition, the withdrawal of drugs, such as benzodiazepines, can cause profound withdrawal reactions, which may contribute to delirium. Second, we hypothesise that there is a process that affects memory negatively for external events but enhances memory for internal events. The physical constraints and social isolation experienced by ICU patients and the life-threatening nature of the illness may increase the experience of hypnagogic hallucinations. Attentional shift during hypnagogic images from external stimuli to internally generated images would explain why ICU patients have such poor recall of external ICU events, but can clearly remember hallucinations and nightmares. Patients describe these memories as being very vivid and this is explored in terms of flashbulb memory formation. The absence of memories for real events on ICU can result in ICU patients remembering paranoid delusions of staff trying to kill them, with little information to reject these vivid memories as unreal. This has implications for patients' future psychological health.

The behavioural and neuronal effects of the chronic administration of benzodiazepine anxiolytic and hypnotic drugs

Benzodiazepine anxiolytic and hypnotic drugs are some of the most widely prescribed drugs in the Western world. Despite this fact, the mechanisms that underlie the development of tolerance to, and dependence upon, benzodiazepines are poorly understood. The aim of this review is to summarize and critically evaluate the experimental evidence relating to the chronic behavioural and neuronal effects of benzodiazepines. Behavioural studies in animals generally indicate that tolerance gradually develops to the muscle relaxant, ataxic, locomotor and anticonvulsant effects of benzodiazepines. The evidence relating to the development of tolerance to the anxiolytic effects of benzodiazepines is less clear. The literature on the possible mechanisms of benzodiazepine tolerance and dependence is large, highly complex and difficult to interpret. The effect of chronic benzodiazepine treatment varies enormously as a function of the benzodiazepine used and the treatment schedule employed. Many studies have demonstrated a down-regulation of benzodiazepine binding sites, although affinity is usually unchanged. The evidence relating to the number and affinity of GABAA binding sites is unclear. Some studies suggest that chronic benzodiazepine administration results in a reduction in the number of Cl- channels associated with the GABAA receptor complex, although it is not clear that the efficacy of the GABA binding site in operating the Cl- channel necessarily changes. There is, however, substantial evidence to support the hypothesis that chronic benzodiazepine treatment results in a reduction in the coupling between the GABAA and benzodiazepine binding sites (the "functional uncoupling hypothesis"). Although some electrophysiological studies suggest that chronic benzodiazepine treatment results in a subsensitivity to GABA, this effect seems to be highly area-specific.

Chronic bretazenil produces tolerance to chlordiazepoxide, midazolam, and abecarnil

The purpose of the present study was to determine if chronic treatment with a nonsedative benzodiazepine partial agonist would confer tolerance to the rate-decreasing effects of other benzodiazepine ligands in a fixed-interval procedure in rats. A separate group of rats was treated chronically with the sedative benzodiazepine full agonist, chlordiazepoxide, for comparison. It was hypothesized that tolerance would develop rapidly to chlordiazepoxide due to loss of reinforcement density at rate-decreasing doses and that there would probably be cross-tolerance to other rate-decreasing benzodiazepine ligands such as midazolam and abecarnil. Because bretazenil does not produce rate decreases, however, it was not expected that tolerance would be found to chlordiazepoxide, midazolam, or abecarnil. After 8-12 weeks of chronic treatment with either chlordiazepoxide or bretazenil, however (final dose of benzodiazepine = 30 mg/kg/day), tolerance was found to the rate-decreasing effects of chlordiazepoxide, midazolam, and abecarnil in both groups. It is concluded that such tolerance was most likely due to a saturation of benzodiazepine receptors by this high-affinity partial agonist.

State-dependent effects of atypical benzodiazepine-receptor agonists

The state-dependent effect of the BZ-receptor agonist diazepam (1.25-10 mg/kg), the partial agonist FG 8205 (0.5-4.0 mg/kg) and the BZ1-receptor agonist zolpidem (0.25-2 mg/kg) were investigated in rats. During daily sessions, animals were trained to acquire FR10 lever pressing for food reinforcement whilst under the influence of the agonists, using an operant technique. Forty-eight hours after the final training session under drug, their performance of the FR10 was evaluated during a test session, carried out following vehicle administration only. Neither diazepam, nor FG 8205 impaired acquisition of the task. In the group treated with 2 mg/kg zolpidem, six out of eight rats failed to learn within 20 sessions, but the smaller doses were without effect on acquisition. When drug treatment was withdrawn, there was evidence that all three of the agonists tested produced state-dependency. This was apparent in the form of longer latencies to obtain reinforcement and decreased lever pressing rates. The significance of these findings are discussed in the context of the relationship between the state-dependent effects of BZ-receptor agonists and their other properties, and the receptor subtypes which might underly these effects.

Social pharmacology: unresolved critical issues

This article describes and analyzes decision-making by patients, physicians, and drug information providers about registered medical drugs. Based on a cognitive psychology perspective, cognitive variables (the individual's mediating system) are assumed to be critical factors determining both patient and physician behavior. The individual's psychological functioning is seen as a continuous reciprocal interaction between behavioral, cognitive, and environmental influences; i.e., an interactional paradigm is applied. The importance of research models including cognitive and situation variables to guide the search for appropriate research methods is stressed. An intensive research strategy with a small sample of respondents will often be necessary. Also, respondents should be asked to describe their reactions to specific medical situations. The drug information sender has to select a set of goals for disseminating information to patients. Among the goals most often selected are: message comprehension, receiver satisfaction, changes in knowledge, attitudes, and drug behavior, as well as health effects. More research is needed on how the patient's mediating system, the actual situation, and the perceived situation steer his search for the use of new drug information. A different set of factors influence the patient's decision to start a medicinal or drug treatment than the factors that influence his decision to continue a treatment. The latter factors include forgetfulness, misunderstandings, and the patient's interpretation of physiological signs. More cognitive-oriented research about drug compliance must be undertaken. In such studies the mediating systems of a group of patients could be considered before and after intervention. There are a great number of types of inappropriate (irrational) prescribing. However, a physician may prescribe rationally in one area but irrationally in another. Face-to-face education of physicians has been shown to be effective in reducing inappropriate prescribing in a number of studies. "Overprescribing" of benzodiazepine has been an issue of intensive professional debate during the last decades. The two groups who criticize and defend the existing use of benzodiazepines build their views on different assumptions about the interaction between mind and brain as well as making different value assumptions regarding the use of a psychotropic drug. There is a need for prescription studies where a cognitive and interactional perspective is combined with an information-processing and a normative perspective. The benzodiazepines dependency problem has provoked lively discussion among professionals and the general public. Long-term benzodiazepine use and personality disorders increase the risk of the patient becoming dependent. A great number of research models have been suggested for the analysis of prescription drug dependency and as guides to the treatment of dependency.(ABSTRACT TRUNCATED AT 400 WORDS)

Biological processes in benzodiazepine dependence

The indications for the benzodiazepines include anxiety, insomnia, muscle spasm and epilepsy and each disorder has a variety of biological substrates. Limbic structures and the neurotransmitters noradrenaline, 5-HT and GABA have all been implicated. Benzodiazepines act on allosteric receptor sites and potentiate the actions of GABA in modulating chloride ionophores across nerve membranes. These effects can be blocked by the benzodiazepine antagonist, flumazenil. The molecular pharmacology of the benzodiazepine-GABA-chloride receptor is complex, with a wide range of different subunits. Animal models of dependence have suggested that the changes associated with long-term benzodiazepine use are related more to receptor-effector coupling than to the receptor characteristics themselves. Thus, benzodiazepine agonists on long-term use lose their efficacy, antagonists become partial inverse antagonists, and inverse agonists increase in efficacy. Various clinical implications are explored, including the use of flumazenil to prevent and to treat benzodiazepine withdrawal syndromes.

Chlordiazepoxide, but not bretazenil, produces acute dependence, as evidenced by disruptions in schedule-controlled behavior

The purpose of the present study was to determine whether the full benzodiazepine (BDZ) agonist chlordiazepoxide (CDAP) and the partial BDZ agonist bretazenil would produce acute dependence in rats, as evidenced by disruptions in fixed-interval responding during precipitated abstinence withdrawal. Doses of CDAP and bretazenil administered acutely were 10, 75, and 100 mg/kg; flumazenil (1-56 mg/kg) was administered 1, 2, 4, or 18 h later. Withdrawal, defined as a significant decrease in fixed-interval responding, was only seen when a high dose of flumazenil was administered 18 h after 100 mg/kg of CDAP. These results support those of others (5) who found that high (75-450 mg/kg) doses of CDAP were required to produce acute physical dependence. That bretazenil did not produce acute physical dependence supports the findings of others (20,23) who report that chronic administration of bretazenil does not result in physical dependence.

Neuropharmacology of a new potential anxiolytic compound, F 2692, 1-(3'-trifluoromethyl phenyl) 1,4-dihydro 3-amino 4-oxo 6-methyl pyridazine. 1. Acute and in vitro effects

F 2692 [1-(3'-trifluoromethyl phenyl) 1,4-dihydro 3-amino 4-oxo 6-methyl pyridazine] exhibited dose-dependent "anxiolytic" properties in the elevated plus-maze and the punished drinking tests in rats. It was also active in the two-compartment test in mice. The "anxiolytic" effects were antagonised by the benzodiazepine antagonists, flumazenil and ZK 93426. The compound exhibited anticonvulsant, sedative, myorelaxant and amnesic effects at doses 3-30 times higher than those required for "anxiolytic" activity. F 2692 has a very low affinity for benzodiazepine binding sites in vitro and in vivo (about 1000 and 160 fold lower than diazepam respectively). In addition it displayed no affinity for GABAA, alpha 2-adrenergic, 5-HT1A or 5-HT2 receptors. These data suggest that F 2692 may be a potential anxiolytic compound with an unusual mechanism of action.

Neuropharmacology of a new potential anxiolytic compound, F 2692, 1-(3'-trifluoromethyl phenyl) 1, 4-dihydro 3-amino 4-oxo 6-methyl pyridazine. 2. Evaluation of its tolerance and dependence producing potential and of its effects on benzodiazepine withdrawal in the elevated plus-maze test in rats

After 21 days administration, diazepam (0.3-3 mg/kg/day) exhibited, 30 min after the last injection, tolerance to the sedative effect and "anxiolytic" activity as recorded in the elevated plus-maze test in rats. A dose-dependent increase of "anxiety" was also observed 24 h after withdrawal from 21 or 90 days of diazepam treatment. In contrast, under the same experimental conditions, F 2692 [1-(3'-trifluoromethyl phenyl) 1,4-dihydro 3-amino 4-oxo 6-methyl pyridazine] (3-30 mg/kg/day) exhibited no tolerance to either the sedative effect or the "anxiolytic" activity and showed no "anxiogenic rebound" response after withdrawal. Chronic diazepam pretreatment for 21 days modified neither the sedative effect nor the dose-dependent "anxiolytic" effect of F 2692. Furthermore, F 2692 could reverse the anxiogenic response after withdrawal from 21 days administration of diazepam. Finally, administration of diazepam for 3 weeks followed by a daily administration of F 2692 for a week induced no increase of "anxiety" 24 h after withdrawal.

A guide to benzodiazepine selection. Part II: Clinical aspects

To suit the specific needs of various clinical situations, selection of an appropriate benzodiazepine derivative should be based on consideration of their different pharmacokinetic and pharmacodynamic properties. Benzodiazepine derivatives that are rapidly eliminated produce the most pronounced rebound and withdrawal syndromes. Benzodiazepines that are slowly absorbed and slowly eliminated are most appropriate for the anxious patient, since these derivatives produce a gradual and sustained anxiolytic effect. Rapidly absorbed and slowly eliminated benzodiazepines are usually more appropriate for patients with sleep disturbances, since the rapid absorption induces sleep and the slower elimination rate may induce less tolerance to the sedative effect. Rational selection of a benzodiazepine for the elderly and for the suspected drug abuser is more problematic. The relevant pharmacokinetic and clinical considerations for these users are discussed. Certain derivatives may possess pharmacodynamic properties not shared by the entire benzodiazepine class; empirical studies have suggested the existence of anti-panic properties for alprazolam and clonazepam, antidepressant properties for alprazolam, and anti-manic properties for clonazepam and possibly lorazepam.

Lack of effect of a small dose of flumazenil in reversing short-term tolerance to benzodiazepines in normal subjects

Twelve normal volunteers received two courses of 7 days of either lorazepam (2 mg every morning; six subjects) or oxazepam (30 mg every morning; six subjects). After one of the courses, 0.2 mg of flumazenil was injected, after the other placebo, using a balanced design and double-blind procedures. A test dose of the lorazepam or oxazepam was administered the day after the flumazenil or placebo. A battery of physiological and psychological tests was applied before and after the dose of benzodiazepine on days 1, 4, 8 and 10. The benzodiazepines had the expected effects on the EEG, and event-related potentials (ERP), impaired several psychological tests and induced drowsiness and relaxation. Some tolerance was seen with respect to anxiolytic effects, some EEG and ERP variables and some psychological tests, but not those of memory. Tolerance tended to be more apparent in the subjects given lorazepam than in the oxazepam-treated subjects. No effects of the small dose of flumazenil in reversing tolerance were apparent.

Cyclopyrrolones, unlike some benzodiazepines, do not induce physical dependence in mice

In a model of physical dependence in mice, treatment with cyclopyrrolones such as zopiclone and suriclone (from 4 to 400 mg/kg/day), did not modify the sensitivity of the gamma-aminobutyric acid (GABA) receptor complex to the partial inverse agonist FG 7142 following their withdrawal, whereas sensitivity changes were observed after treatment and withdrawal from some benzodiazepines (e.g. lorazepam, diazepam, flunitrazepam and triazolam). These data suggest that, in contrast to some benzodiazepines, zopiclone and suriclone may not produce physical dependence.

The prolonged benzodiazepine withdrawal syndrome: anxiety or hysteria?

In an attempt to establish whether prolonged withdrawal symptoms after stopping intake of benzodiazepines is caused by return of anxiety, hysteria, abnormal illness behaviour or the dependence process itself producing perhaps a prolonged neurotransmitter imbalance, a group of such patients suffering prolonged withdrawal symptoms (PWS) was compared on a range of psychophysiological measures with matched groups of anxious and conversion hysteria patients and normal controls. It was found that the psychophysiological markers of anxiety were not marked in the PWS group; nor were the averaged evoked response abnormalities found to be associated with cases of hysterical conversion in evidence. The PWS group were hard to distinguish from normal controls on the basis of psychophysiological measures and thus it was felt to be unlikely to be an affective disturbance. It was concluded that PWS is likely to be a genuine iatrogenic condition, a complication of long-term benzodiazepine treatment.

Intervention against long-term use of hypnotics/sedatives in general practice

The aim of the study was to evaluate the efficiency of different strategies of intervention to reduce prescription of hypnotics/sedatives in general practice. All 356 general practitioners in the county of Aarhus, Denmark, were divided in three groups. One group received personal information at meetings, another received written material about proper use of hypnotics/sedatives and information about their own prescription rate, and the third group constituted a control group. The prescription rate was recorded before and after the intervention. There was a general decline in the prescription rate recordings, but there were no significant differences between the intervention groups and the control group.

The history of benzodiazepine dependence: a review of animal studies

This article provides a historical review of the animal literature relating to the development of tolerance to the behavioral effects of benzodiazepines, and the incidence of biochemical and behavioral changes that result from termination of benzodiazepine treatment (spontaneous withdrawal responses). It charts the slow emergence of a pertinent animal literature and highlights conclusions that were prevalent in 1963 (at the introduction of diazepam), 1973 (at the introduction of lorazepam), 1980 and the present day. For 25 years the animal literature has lagged behind the clinical literature, but recent studies into the neurochemical mechanisms of benzodiazepine dependence and possible treatments for withdrawal responses suggest that, at last, animal experiments may be about to make a substantial contribution.

Changes in seizure threshold and aggression during chronic treatment with three anticonvulsants and on drug withdrawal

Sodium phenobarbitone (20 and 70 mg/kg) had a significant anticonvulsant action against pentylenetetrazole-induced seizures, which persisted for 21 days of treatment. On drug withdrawal there was a significant decrease in seizure threshold below control level 24-48 h after the last dose of 70 mg/kg. Phenytoin (40 mg/kg) had a significant anticonvulsant action after 7 days of treatment and this persisted for 21 days of treatment. On drug withdrawal there was a significant decrease in seizure threshold 48 h after the last dose. Lorazepam (0.1 mg/kg) had a significant anticonvulsant action, but the group tested after 21 days of treatment did not differ from the controls, indicating that tolerance had developed to this effect; on drug withdrawal there was a decrease in seizure threshold from 24 to 72 h. The only drug to increase aggressive behaviour was sodium phenobarbitone (70 mg/kg); this reached significance after 14 and 21 days of treatment and occurred 8 h after drug administration; 0.5 h after drug administration phenobarbitone (70 mg/kg) abolished aggressive behaviour. After 7 days of treatment phenobarbitone (70 mg/kg) increased social behaviour 0.5 h after administration and this was still increased after 21 days of treatment. On drug withdrawal, there were no changes in aggressive behaviour, but there were significant decreases in social behaviour 24 and 48 h after phenobarbitone (70 mg/kg) withdrawal and 24, 48 and 72 h after lorazepam (0.1 mg/kg) withdrawal.

Chronic diazepam treatment in rats causes long-lasting changes in central [3H]-5-hydroxytryptamine and [14C]-gamma-aminobutyric acid release

The effects of chronic diazepam administration to rats on the central release of [3H]-5-hydroxytryptamine ([3H]-5-HT) and [14C]-gamma-aminobutyric acid ([14C]-GABA, ex vivo) were examined. Chronic (5 and 21 days) administration of diazepam (4 mg kg-1 i.p. daily for 21 days) reduced the K-evoked (20 mM KCl) release of [3H]-5-HT from frontal cortex by approximately 50%. Remarkably, this decrease was still present 1 week after diazepam withdrawal. Chronic diazepam treatment did not significantly affect hippocampal [3H]-5-HT release but after 21 days the K-evoked release of [14C]-GABA was more than doubled and remained elevated 30 h after withdrawal; it returned to control levels after 1 week, and decreased below control levels after 2 weeks. This study indicates that chronic diazepam treatment produces striking changes in transmitter release in rats that persist long after treatment has ceased.

Anxiogenic-like action of caerulein, a CCK-8 receptor agonist, in the mouse: influence of acute and subchronic diazepam treatment

Effects of caerulein, a cholecystokinin octapeptide (CCK-8) receptor agonist, on exploratory activity of mice were investigated. Exploratory and locomotor activity of animals were measured using elevated plus-maze and open field tests. The systemic administration of caerulein at non-sedative doses (100 ng/kg-1 micrograms/kg i.p.) resulted in a significant decrease in the exploratory activity of mice. This effect was completely blocked by proglumide, a CCK-8 receptor. Acute treatment with low doses (0.1-0.75 mg/kg i.p.) of diazepam did not attenuate the anxiogenic-like effect of caerulein, but at more high doses of diazepam the coadministration depressed locomotor activity in mice. After subchronic diazepam treatment (2.5 mg/kg once a day, 10 days, i.p.) tolerance was developed toward the sedative effect of diazepam, and 72 h after withdrawal of the drug the animals showed increased anxiety in the plus-maze test. 30 min after the last injection procedure the anxiogenic-like effect of caerulein (500 ng/kg i.p.) on exploration was absent in both diazepam or vehicle groups. However, 72 h after the last pretreatment injection caerulein (500 ng/kg i.p.) reduced significantly the exploratory activity in control group, whereas it was inactive after diazepam withdrawal. The results obtained in this study support the hypothesis that endogenous CCK-8 an CCK-8 receptors are involved in the neurochemistry of anxiety and the anxiolytic action of benzodiazepine tranquillizers.

Benzodiazepines: tolerance, dependence, abuse, and addiction

Many recent studies have clearly documented the development of tolerance, dependence, and addiction to benzodiazepines. In spite of these studies and reviews of the literature, confusion remains regarding the risk and benefits of the use of benzodiazepines in medical practice. The source of the confusion arises in part from the lack of clarity in the definitions of tolerance, dependence, and addiction. The distinctions among these important terms are frequently obscured in research studies and, especially, in clinical practice. In addition, the practice of separating medical from nonmedical populations in reports of benzodiazepine dependence is misleading. The overlap between medical and nonmedical benzodiazepine users is large, so that many of these individuals fall into both categories. These and other points should be considered as serious questions to the safety and freedom from dependence and addiction in any drug-using population.

A theory of benzodiazepine dependence that can explain whether flumazenil will enhance or reverse the phenomena

Repeated administration of benzodiazepines (BDZs) produces dependence in man and animals and this is reflected in the phenomena of tolerance and withdrawal responses. In BDZ-dependent animals the BDZ-receptor antagonist flumazenil (Ro 15-1788) reverses the increased anxiety and decreased seizure threshold seen when benzodiazepine treatment is withdrawn. In contrast are reports that flumaenil enhances BDZ-withdrawal responses. Indirect influences on the direction of flumazenil's effects on anxiety are the duration and dose of BDZ treatment, whether tolerance has developed to its anxiolytic effect and whether there is an anxiogenic response on drug withdrawal. However, we conclude that the crucial factor is the anxiety level of the animal: when this is high flumazenil becomes anxiolytic; when this is low flumazenil is anxiogenic. These bidirectional effects of flumazenil can be seen in drug-naive and BDZ-dependent animals. We propose a theory of benzodiazepine dependence that can account for anxiogenic responses on drug withdrawal and for flumazenil's bidirectional effects; central to this theory is the assumption that flumazenil normalises the benzodiazepine receptor, returning it to a baseline state. Thus it is whether an animal's score lies above or below this baseline that will determine the direction of flumazenil's effect. The clinical implications of this theory are discussed. We suggest that during the development of benzodiazepine dependence, two independent adaptive biochemical mechanisms are triggered: one underlying the development of tolerance to the anxiolytic responses, the other underlying the incidence of increased anxiety on drug withdrawal. It is only changes in the latter that are induced by the administration of flumazenil.

Determination of pharmacodynamics of diazepam by quantitative pharmaco-EEG

The relationship between the quantitative EEG variables and plasma levels after the administration of diazepam (DZ) or N-desmethyldiazepam (synthesized NDDZ) was evaluated by simultaneously measuring the power spectra for EEG with two biological markers and plasma concentrations. After a single DZ administration, the EEG change corresponding to sedation appeared rapidly and showed a short duration. A close relationship was found between these effects and changes in the DZ plasma concentrations. DZ and synthesized NDDZ had the same pharmacodynamic characteristics, but the main metabolic product of DZ (metabolite NDDZ) showed a different pharmacokinetic profile. A multiple administration of DZ or synthesized NDDZ caused some reduction in sedation at the steady-state. These results led to the conclusions that a single administration of DZ causes sedation of a short duration, and the main metabolic product of DZ (metabolite NDDZ) does not seem to contribute to sedation. In addition, the reduction in the pharmacological effect after continuous treatment with DZ depends not on autoinduction or interference, but on acute tolerance or adaptation.

Panic attacks and major depression after discontinuation of long-term diazepam abuse

A case is described of a patient with a history of several years of diazepam abuse (in the last 24 months at dosages of 120 mg/d). A tapering schedule was carried out during a 12-day stay in the hospital in which the diazepam dosage was reduced by a fixed quantity every day, corresponding to about ten percent of the initial dosage. Five days after discharge from the hospital the patient experienced panic attacks, for the first time, which continued until 13 days after discharge. By the 40th day, the patient was experiencing a major depressive episode, which improved after administration of clomipramine therapy. We suggest that a relatively quick withdrawal schedule (ten percent per day) is probably inadequate in preventing withdrawal reactions to long-acting benzodiazepines taken in high doses for an extended period of time.

Prevalence of benzodiazepine abuse and dependence in psychiatric in-patients with different nosology. An assessment of hospital-based drug surveillance data

Frequencies of abuse and dependence assessed continuously within a drug surveillance system were analysed as a contribution to risk-benefit evaluations of benzodiazepines (BZDs). In 4.7% of 15,296 patients admitted to psychiatric hospitals between 1980 and 1985, BZDs had been involved in some kind of abuse or dependence. Primary BZD dependence, defined as physical dependence on BZDs in patients who had not been dependent before, was observed in about 1% of admitted patients. Linking these data with psychiatric diagnoses revealed a high risk of primary BZD dependence for in-patients (11.8%) with anxiety neurosis (ICD-9, 300.0), and a lower risk for neurotic (300.4) and for endogenous depressives (296.1) (risk 3.7% and 2.7% respectively). Older age was also related to primary BZD dependence. For depressive in-patients, the risk was twice as high in females as in males. Anecdotal observations advocate more systematic investigation of the emotional effects of long-term therapy with BZDs.

Lack of anticonvulsant tolerance with RU 32698 and Ro 17-1812

Possible development of anticonvulsant tolerance to three benzodiazepine receptor ligands was assessed in mice using an i.v. infusion of pentylenetetrazol as the convulsive stimulus. Extensive tolerance developed rapidly in the case of diazepam (0.35 mg/kg b.d. or 1.5 mg/kg b.d.). No significant tolerance was seen with the imidazopyrimidine derivative RU 32698 (9 mg/kg b.d.) or the partial agonist benzodiazepine Ro 17-1812 (1 mg/kg b.d.) These results provide further support for the hypothesis that partial agonists at the benzodiazepine receptor induce less tolerance than full agonists.

The damnation of benzodiazepines

It is argued that there are two kinds of benzodiazepine dependence: a therapeutic and a morbid kind. The therapeutic dependence is acceptable in that it mitigates the clinical manifestations in patients with long-standing and fluctuating anxious-depressive symptoms. The morbid dependence is an unfortunate complication which can arouse therapeutic concern because it ties patients to an excessive dosage, unless the penalty of a sometimes grim abstinence syndrome is paid on drug reduction. The present, often strident and threatening, damnation of benzodiazepines oversteps the mark and causes avoidable misery to patients whose well-being has become largely and therapeutically dependent on the drug.

Withdrawal, tolerance and sensitization after a single dose of lorazepam

Forty-eight hours after a single dose of lorazepam (0.25 mg/kg), there was tolerance to the lorazepam-induced reduction of locomotor activity in the holeboard; but no tolerance to the reductions in exploratory head-dipping or rearing. Mice tested undrugged at this time showed significant hyperactivity and increased rearing, indicating withdrawal responses, but no change in head-dipping. In the elevated plus-maze, no tolerance could be detected to the effects of lorazepam (0.25 mg/kg) when the mice were tested 48 hr after an initial dose; in fact, there was a trend towards enhanced effects in this group. When mice were tested undrugged 24, 48 or 72 hr after a single dose of lorazepam there was an increase in the % time spent on the open arms, compared with controls, that reached significance for the 24 hr group. This indicates a sensitization to the anxiolytic effects of lorazepam, as assessed in the plus-maze. These results demonstrate long-lasting effects of even a single dose of lorazepam.

The natural history of tolerance to the benzodiazepines

Dependence on benzodiazepines following continued use is by now a well-documented clinical phenomenon. Benzodiazepines differ in their dependence potential. The present studies were aimed at examining the possibility that differential rates of tolerance development might account for differences in dependence risk. Four studies are reported. The first three studies concerned normal subjects. The development of tolerance over a fifteen day period was demonstrated for three different benzodiazepines (ketazolam, lorazepam and triazolam) using two paradigms. Tolerance in terms of a reduction in effectiveness of a repeated given dose was most notable for the benzodiazepine with a medium elimination half-life (lorazepam) for physiological, behavioural and subjective measures. In the case of the drug with the longest elimination half-life (ketazolam) reduction in effectiveness could only be assumed to be occurring if account was taken of the steady increase in plasma concentrations of active metabolites. For this drug it seemed that the physiological measures were those most likely to demonstrate the development of tolerance. Although triazolam showed few significant drug effects on this paradigm (testing being 12 hours after ingestion of this short half-life benzodiazepine), tolerance was seen to develop on some subjective measures. Using an alternative method of testing tolerance, assessing responses to a diazepam challenge dose, a high degree of tolerance on two-thirds of the measures was observed in subjects when pretreated with the benzodiazepine with the most marked accumulation of active metabolites (ketazolam). The other two drugs also led to tolerance development on a range of measures; this was more marked for lorazepam than triazolam. Blunting of the growth hormone response to diazepam was the most sensitive and reliable method of detecting tolerance to the benzodiazepines. Symptoms on discontinuation of the two weeks' intake of the benzodiazepines were marked for all the drugs but unrelated to either the tolerance induced or the elimination half-life of the particular drug. A further clinical study revealed that tolerance persisted in a group of long-term benzodiazepine users for between four months and two years following complete abstinence from the drug. These patients appeared to be less affected by diazepam in terms of its commonly observed subjective effects, regardless of their original medication. These ex-long-term users of benzodiazepines were, however, more likely to manifest two specific types of effects--immediate 'symptom' reduction and exacerbation of 'withdrawal symptoms' over the subsequent week.(ABSTRACT TRUNCATED AT 400 WORDS)

Long-term treatment of anxiety: benefits and drawbacks

Anxiety disorders are common conditions, often chronic, occurring in the general population with a prevalence of about 3%. Long-term use of tranquilizers varies from 0.5% of the total adult population in Sweden and 1.3% in Denmark to 3.1% in Great Britain and 5% in France. This use is tending to become more and more long-term. Long-term efficacy of benzodiazepine medication has not been established. Adverse effects include psychomotor and cognitive impairment, especially in the elderly; some, but not all, effects show tolerance. Some impairment can be demonstrated even after years of use. Rebound and withdrawal reactions after long-term use are common. Practical guidelines to minimize long-term use are suggested.

Anxiogenic effects in benzodiazepine withdrawal are linked to the development of tolerance

Rats were tested in the elevated plus-maze test of anxiety after a probe injection of chlordiazepoxide (CDP 5 mg/kg) following short-term (5 days) or long-term (20 days) pretreatment with 5 or 20 mg/kg/day. After short-term pretreatment with either dose, the probe dose had anxiolytic effects (it increased the % number of entries, and % of time spent, on the open arms). After long-term pretreatment with either dose of CDP there was tolerance to these effects. When the rats were tested 24 hours after their last dose of CDP, there was no indication of spontaneous withdrawal responses in the rats from the short-term pretreatment groups, but the rats in the long-term pretreatment groups showed increased anxiety (decreases in the % number of entries, and the % of time spent, on the open arms, compared with controls). These results support suggestions that the development of tolerance and the incidence of withdrawal anxiety may both be manifestations of the underlying changes occurring during drug dependence.