Performance effects of diazepam during and after prolonged administration

Diazepam Tolerance Effects on Vestibular Function Testing, Part I: Saccadic Parameters during Electronystagmography

Objectives:

Benzodiazepines, particularly diazepam (DZ), are used in clinical practice to suppress acute vestibular symptoms. There have been limited studies looking at the effects of tolerance to DZ on parameters designed to measure the integrity of the vestibular system and its interaction with the oculomotor and balance systems.

Methods:

In a double-blinded, repeated-measures design, we randomized 30 young healthy men into one of two treatment groups (diazepam and placebo) and assessed with electro-oculography the effects of clinical divided doses of DZ on saccadic eye movements and sedation over 16 days.

Results:

Only sedation and saccadic latency were significant (p < .05) for treatment group, indicating selective effects on different central nervous system mechanisms. No significant effect for time was seen in any of the variables measured. Bonferroni t-test comparisons of the DZ group among 3 days were significant (p < .017) between baseline and day 3 for saccadic latency and accuracy and between day 3 and day 16 for self-ratings of sedation.

Conclusions:

Saccadic latency and accuracy and sedation ratings appear to be more sensitive to changes over time and less affected by subject variability than saccadic eye velocity. It remains questionable whether patients who have been on DZ for acute or extended periods of time need to discontinue the drug 48 hours before testing.

An evaluation of persisting cognitive effects after withdrawal from long-term benzodiazepine use

Twenty participants with self-reported long-term benzodiazepine use (mean 108 months) who had previously withdrawn from medication (mean 42 months) were administered a battery of neuropsychological tests. Each long-term user was case matched for age, sex, and education to two control participants who reported never taking benzodiazepines (those with and those without anxiety). The results indicated that long-term benzodiazepine use may lead to impairments in the areas of verbal memory, motor control/performance, and nonverbal memory but not visuospatial skills and attention/concentration. The length of abstinence (> 6 months) indicates that these impairments persist well beyond cessation of benzodiazepine use. However, observed impairments in the area of nonverbal memory were not solely attributable to benzodiazepine use and may be influenced by the elevated anxiety levels present in both the case and the anxious control group.

Cognitive effects of long-term benzodiazepine use: a meta-analysis

INTRODUCTION

While benzodiazepines are the most widely used psychotropic drugs, there are relatively few studies that have examined deficits in cognitive functioning after long-term use. The literature that is available is difficult to interpret due to conflicting results as well as a variety of methodological flaws.

OBJECTIVE

To systematically evaluate and integrate the available research findings to determine the effect of long-term benzodiazepine use on cognitive functioning using meta-analytical techniques.

METHODS

Thirteen research studies that employed neuropsychological tests to evaluate cognitive performance after long-term use of benzodiazepine medication met inclusion criteria. The neuropsychological tests employed in these 13 studies were each categorised as measuring one of 12 cognitive domains. Separate effect sizes were calculated for each of the 12 cognitive categories. Each study was only allowed to contribute one effect size to each cognitive category by averaging together the effect sizes from the same study if more than one type of test was used to measure a particular category. This strategy resulted in equal weight being given to each study per category, regardless of the number of tests in that category.

RESULTS

The overall mean number of patients who were benzodiazepine users was 33.5 (SD +/- 28.9) and the mean number of controls was 27.9 (SD +/- 19.6). The duration of benzodiazepine use ranged from 1 to 34 (mean 9.9) years. Long-term benzodiazepine users were consistently more impaired than controls across all cognitive categories examined, with effect sizes ranging in magnitude from -1.30 to -0.42. The mean weighted effect size was -0.74 (SD +/- 0.25). None of the effect sizes had 95% CIs that spanned zero and, therefore, all of these effects were significant and different to zero.

CONCLUSION

Moderate-to-large weighted effect sizes were found for all cognitive domains suggesting that long-term benzodiazepine users were significantly impaired, compared with controls, in all of the areas that were assessed. However, this study has several limitations, one being that it includes a relatively small number of studies. Further studies need to be conducted; ideally, well designed, controlled studies that thoroughly investigate certain areas of cognitive functioning and present data in such a way so as to be amenable to inclusion in a meta-analysis. Incorporating the information from these studies into a larger meta-analysis would allow for a more thorough and statistically sound investigation of the effects of moderator variables. The observation that long-term benzodiazepine use leads to a generalised effect on cognition has numerous implications for the informed and responsible prescription of these drugs.

Absence of neuropsychologic deficits in patients receiving long-term treatment with alprazolam-XR for panic disorder

Studies to date on the effects of benzodiazepines on neuropsychologic function have yielded conflicting data with respect to the type, severity, and duration of deficits that may be induced by these agents. As part of a placebo-controlled trial of alprazolam-XR (extended release) administered in combination with cognitive-behavioral therapy in patients with panic disorder, a battery of tests was used to measure neuropsychologic function. Thirty-eight outpatients were randomly assigned to receive either alprazolam-XR or placebo. Dosages were titrated up so that the alprazolam group (N = 18) received a mean dose of 4 mg/day (reduced in two patients because of sedative side effects). Neuropsychologic function after 6 weeks of therapy at the target dosage was compared with baseline assessments in each group. Both groups showed a statistically significant improvement from baseline to repeated assessments on measures of attention, executive functioning, psychomotor speed, and visual memory (p < 0.001); these gains were attributed to a practice effect. No significant changes were noted in measures of learning, verbal memory, or reaction time, and neither group showed any deterioration from baseline to retesting in any aspect of neuropsychologic function. These findings call into question the assumption that long-term benzodiazepine therapy produces significant neuropsychologic deficit in patients with diagnosed anxiety disorders.

Lack of cognitive recovery following withdrawal from long-term benzodiazepine use

Twenty-one patients with significant long-term therapeutic benzodiazepine (BZ) use, who remained abstinent at 6 months follow-up after successfully completing a standardized inpatient BZ withdrawal regime, and 21 normal controls matched for age and IQ but not for anxiety, were repeatedly tested on a simple battery of routine psychometric tests of cognitive function, pre- and post-withdrawal and at 6 months follow-up. The results demonstrated significant impairment in patients in verbal learning and memory, psychomotor, visuo-motor and visuo-conceptual abilities, compared with controls, at all three time points. Despite practice effects, no evidence of immediate recovery of cognitive function following BZ withdrawal was found. Modest recovery of certain deficits emerged at 6 months follow-up in the BZ group, but this remained significantly below the equivalent control performance. The implications of persisting cognitive deficits after withdrawal from long-term BZ use are discussed.

The effects and after effects of the α2-adrenoceptor antagonist idazoxan on mood, memory and attention in normal volunteers

Idazoxan, an α( 2)-adrenoceptor antagonist, is an effective antidepressant with a mode of action different from that of conventional antidepressants. As it is used as an antidepressant it is important to know whether there are any unwanted CNS side effects. Study of its effects will also provide information on the relationship between noradrenergic function and mood and performance. Twelve normal male volunteers who were given the drug (40 mg orally three times daily for 21 days) were compared with 12 matched controls. A computerized test battery was used to assess mood and various aspects of memory and attention. Many of the tests of memory and attention in the battery have been widely used over the last 20 years, and in addition two new selective attention tasks were included. The subjects were tested 3 days before starting the drug, on days 3 and 17 while on the drug, and after they had stopped taking the drug (4 days after and 24 days after). Control subjects followed a similar testing schedule. The results showed that the drug had no effect on mood, logical reasoning, retrieval from semantic memory or sustained attention. However, the drug did improve one aspect of selective attention (the place repetition effect), although this effect was only observed on the third day on the drug. Overall, the results suggest that idazoxan produces selective performance improvements, and that the measures of selective attention used here may be more sensitive indicators of drug effects than some of the traditional tasks currently in use.

The pharmacology of human anxiety

The human pharmacology of anxiety disorders, including panic disorder, is detailed. The major theories center around the role of benzodiazepine receptor, noradrenergic and serotonergic dysfunction. The contribution that challenge tests with lactate, hyper- and hypocapnia, beta- and alpha-2-adrenoceptor agonists, peptides, pentylenetetrazol, and caffeine make to our understanding of the biological basis of anxiety and these major theories are described and discussed.

Pharmacological mechanisms of benzodiazepine withdrawal

The pharmacology of the benzodiazepine receptor is unusual in relation to other receptors in that there exist three types of ligand: agonists (e.g. diazepam), which are anxiolytic and anticonvulsant; antagonists (e.g. flumazenil), which are neutral; and inverse agonists (e.g. FG 7142), which are anxiogenic and proconvulsant. Chronic administration of agonists leads to tolerance and withdrawal, and produces a global shift in benzodiazepine receptor function with attenuation of agonist and enhancement of inverse agonist actions. These changes appear without alterations in receptor number or affinity, and may reflect a shift in efficacy, "withdrawal shift", at the receptor. Treatment with flumazenil during benzodiazepine agonist administration, or even in the period after the last dose, can prevent or reverse this efficacy shift as indicated by a lack of sensitization to inverse agonists. The clinical implications of these findings are discussed.

Cognitive functioning in lead workers

In a cross sectional study of occupational exposure to inorganic lead 91 men performed a series of microcomputer based tasks assessing sensor motor reaction time, memory, attention, verbal reasoning, and spatial processing. Performance on the tasks was studied in relation to three ranges of blood lead concentration (low, less than 20 micrograms/dl; medium, 21-40 micrograms/dl; and high, 41-80 micrograms/dl) and exposure response correlations for blood lead concentration, zinc protoporphyrin (ZPP) (range 7-210 micrograms/dl), and urinary aminolaevulinic acid (ALA) (range 0.5-22.0 mg/l). The results show that the high group were impaired on most of the tasks used and, in general, the magnitude of the impairment correlated better with blood lead concentration than ZPP or urinary ALA. An examination of the patterns of task impairment indicated a general slowing of sensory motor reaction time which was relatively independent of the nature of the cognitive functions being tested. There was some evidence, however, suggesting mild impairment of attention, verbal memory, and linguistic processing. In general, workers with high blood lead concentrations showed clear impairment of sensory motor functions in the absence of correspondingly strong evidence for impaired processing and memory functions. It is argued that a general slowness in responding may underlie many previous reports of widespread cognitive impairment in lead workers.

Benzodiazepine prescriptions and therapist non-compliance

In an investigation of benzodiazepine (BDZ) prescription patterns, psychiatrists in private practice were found to exhibit "therapist non-compliance" with regard to general medical recommendations for BDZ use. The findings indicate that BDZ prescriptions in general (53% among patients treated with psychotropics) as well as long-term treatment of patients (37%) are quite common among private practice psychiatrists. BDZ treatment is not restricted to "minor psychiatric disorders", and contrary to the guidelines, even patients with substance dependence are not excluded. A positive association was found for BDZ use and patients' self-reported symptoms and health complaints, the number of other medications prescribed and age. In a discussion of therapist non-compliance it is proposed that this may be a consequence of a symptom-based treatment model, individual health concepts, the doctor-patient relationship and physician's cost-benefit analysis. Thus, psychiatrists' non-compliance may reflect to some extent a case-oriented treatment rationale.

Cognitive impairment in long-term benzodiazepine users

In view of the very extensive and often prolonged use of benzodiazepines in therapeutic practice, this study was designed to investigate whether or not cognitive ability is impaired in long-term benzodiazepine users, and to determine the nature and extent of any deficit. Fifty patients currently taking benzodiazepines for at least one year, thirty-four who had stopped taking benzodiazepines, and a matched control group of subjects who had never taken benzodiazepines or who had taken benzodiazepines in the past for less than one year were administered a battery of neuropsychological tests designed to measure a wide range of cognitive functions. It was found that patients taking high doses of benzodiazepines for long periods of time perform poorly on tasks involving visual-spatial ability and sustained attention. This is consistent with deficits in posterior cortical cognitive function.

Beta-carbolines as tools in memory research: human data with the beta-carboline ZK 93426

The discovery of substances which bind with high affinity to benzodiazepine receptors but have no pharmacological effects (antagonists) or effects opposite to those of benzodiazepines (inverse agonists) have introduced a new approach to elucidating mechanisms underlying memory and other cognitive processes. Since benzodiazepines induce anterograde amnesia and sedation, these substances should show an opposite effect and so enhance memory and/or increase vigilance. In the present report we present data obtained in humans with a benzodiazepine receptor antagonist with weak inverse agonist properties, ZK 93426. The drug was given intravenously to human volunteers in double-blind, placebo-controlled designs and performance on several psychometric tests was evaluated. In a general estimation of behavioural changes volunteers experienced a stimulatory, activating effect of the drug. An improvement was observed in two cognitive tasks, the logical reasoning task and the pictures difference task, which estimate concentration and attentional processes respectively. No effects were found in a letter cancellation test or in time estimation. In another study utilizing EEG recording, we demonstrated that ZK 93426 increased wakefulness (vigilance) in healthy subjects during the daytime. The effect of ZK 93426 upon memory processes was also investigated utilizing a visual memory test and word lists. A slight improvement in some memory processes, especially long-term retrieval, was found. The present data suggest that benzodiazepine receptor antagonists with weak inverse intrinsic activity possess some effects opposite to those of benzodiazepines.

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)

Selective effect of lithium on cognitive performance in man

The effects of lithium on psychomotor performance were examined in six healthy male volunteers (aged 26-31 years) and compared with those of a similar control population. Three computerised psychomotor tests (serial reaction time, semantic reasoning and syntatic reasoning) were administered before lithium, after 5 and 22 days of lithium carbonate (800 mg/d) and 4 days and 1 month after stopping the lithium. The only significant effect was an impairment of semantic reasoning during the chronic (22 day) test. This suggests a selective effect of lithium on associative mental tasks and may explain the subjects' experience of slowing in recall of object names whilst taking lithium.