Comparison of the effect of zopiclone and brotizolam on sleep EEG by quantitative evaluation in healthy young women

Assessing sleep-wake survival dynamics in relation to sleep quality in a placebo-controlled pharmacological intervention study with people with insomnia and healthy controls

RATIONALE

The mechanisms underlying impaired sleep quality in insomnia are not fully known, but an important role for sleep fragmentation has been proposed.

OBJECTIVES

The aim of this study is to explore potential mechanisms of sleep fragmentation influencing alterations of perceived sleep quality.

METHODS

We analyzed polysomnography (PSG) recordings from a double-blind crossover study with zopiclone 7.5 mg and placebo, in elderly participants with insomnia complaints and age-matched healthy controls. We compared survival dynamics of sleep and wake across group and treatment. Subsequently, we used a previously proposed model to estimate the amount of sleep onset latency (SOL) misperception from PSG-defined sleep fragmentation. Self-reported and model-estimated amount of SOL misperception were compared across group and treatment, as well as model prediction errors.

RESULTS

In the zopiclone night, the average segment length of NREM sleep was increased (group F = 1.16, p = 0.32; treatment F = 8.89, p < 0.01; group x treatment F = 0.44, p = 0.65), while the segment length of wake was decreased (group F = 1.48, p = 0.23; treatment F = 11.49, p < 0.01; group x treatment F = 0.36, p = 0.70). The self-reported and model-estimated amount of SOL misperception were lower during the zopiclone night (self-reported group F = 6.08, p < 0.01, treatment F = 10.8, p < 0.01, group x treatment F = 2.49, p = 0.09; model-estimated F = 1.70, p = 0.19, treatment F = 16.1, p < 0.001, group x treatment F = 0.60, p = 0.55). The prediction error was not altered (group F = 1.62, p = 0.20; treatment F = 0.20, p = 0.65; group x treatment F = 1.01, p = 0.37).

CONCLUSIONS

Impaired subjective sleep quality is associated with decreased NREM stability, together with increased stability of wake. Furthermore, we conclude that zopiclone-induced changes in SOL misperception can be largely attributed to predictable changes of sleep architecture.

Effects of eszopiclone and zolpidem on sleep-wake behavior, anxiety-like behavior and contextual memory in rats

At present, eszopiclone and zolpidem are the most commonly prescribed drugs for treating insomnia. Despite the established relationship between sleep disturbance and anxiety, it remains unknown whether targeted treatment for insomnia may affect acute anxiety. Therefore, the objective of this study was to examine the effects of three different doses (1, 3, and 10mg/kg) of eszopiclone and zolpidem on the states of sleep and wakefulness, levels of anxiety-like behavior, and long-term contextual memory in footshock-induced anxious rats. The results of this study demonstrated that the administration of eszopiclone and zolpidem both were equally effective in attenuating footshock stressor-induced suppression of slow-wave sleep (SWS). The administration of eszopiclone at 1mg/kg or zolpidem at 1 and 3mg/kg doses showed a tendency for attenuating stressor-induced suppression of REM sleep. However, the REM sleep attenuating effects of these drugs disappeared when they were administered at higher doses. The administration of eszopiclone at 3 and 10mg/kg doses and zolpidem at all three doses reduced the power of electroencephalographic theta band frequencies during wakefulness. In addition, the administration of eszopiclone at 1 and 3mg/kg doses suppressed stressor-induced anxiety-like behavior. The administration of zolpidem at 1, 3, or 10mg/kg doses was not effective in attenuating stressor-induced anxiety-like behavior. Contextual memory after administration of eszopiclone at 1mg/kg dose had no effects, but was reduced significantly with increased dosage. Contextual memory after administration of zolpidem, at all three doses, was severely disrupted. The results of this study suggest that eszopiclone at a low dose could be used effectively to control anxiety and anxiety-induced insomnia.

The impact of age on the hypnotic effects of eszopiclone and zolpidem in the guinea pig

RATIONALE

Eszopiclone and zolpidem are hypnotics that differentially affect sleep and waking states in adult animals. Therefore, it was of interest to compare their effects on the states of sleep and wakefulness in aged animals.

OBJECTIVES

Our objective was to determine the responses to eszopiclone and zolpidem vis-à-vis sleep and waking states in aged guinea pigs and to compare them with the effects of these hypnotics in adult animals.

METHODS

Aged guinea pigs were prepared to monitor sleep and waking states and to perform a frequency analysis of the EEG. Eszopiclone and zolpidem were administered intraperitoneally (1, 3, and 10 mg/kg).

RESULTS

Eszopiclone produced a more rapid and greater increase in NREM sleep as well as longer duration episodes of NREM sleep compared with zolpidem. There was also a significant increase in the latency to REM sleep with eszopiclone, but not with zolpidem. EEG power during NREM sleep increased in the delta band and decreased in the theta band following eszopiclone administration, whereas zolpidem had no effect on any of the frequency bands analyzed.

CONCLUSIONS

In aged as well as adult guinea pigs, eszopiclone is a more effective hypnotic insofar as it produces a shorter latency to NREM sleep, a greater amount of NREM sleep and EEG delta waves. Differences in the effects produced by eszopiclone and zolpidem as a function of the aging process likely reflect the fact that they bind to different subunits of the GABA(A) receptors, which are differentially reactive to the aging process.

Ceiling and floor effects in sleep research

Ceiling and floor effects dictate that the efficacy of sleep-promoting stimuli should be proportional to the degree of pre-stimulus sleep impairment. This review addressed CF effects in polysomnographic research involving hypnotic drugs and exercise. Correlations of placebo/baseline levels of sleep with changes in sleep following hypnotic or exercise treatment were assessed across both literatures. CF effects were further addressed by comparing sleep-promoting effects of hypnotics vs exercise, after ANCOVA control for substantial baseline differences reported in studies of these stimuli. Significant correlations between placebo-baseline levels and sleep changes were observed following both hypnotic and exercise stimuli. Indeed, approximately 60% of the variance in improvement in sleep latency (SOL), wakefulness after sleep onset (WASO) and total sleep time (TST) following hypnotic treatment was associated with differences in baseline levels. ANCOVAs revealed significantly greater decreases in SOL and WASO following hypnotics compared with exercise. However, no significant difference between stimuli was found for TST, and exercise elicited a significantly greater increase in slow wave sleep. Similar results were found when a comparison between hypnotics and exercise was limited to good sleepers. The results show powerful CF influences on sleep responses to hypnotics and exercise and suggest a need for comparing these treatments in poor sleepers.

Zopiclone, but not brotizolam, impairs memory storage during sleep

We compared the effect of a single bedtime dose of two short half-time hypnotics, brotizolam (0.25 mg) and zopiclone (7.5 mg), on memory storage during sleep in a double blind, placebo-controlled, three-way crossover design trial in eight healthy volunteers. Memory was evaluated using a standard word list free-recall test learned before the bedtime dose by the subjects, who were asked to remember the list the following morning. Digit Symbol Substitution Test revealed no residual sedation by brotizolam or zopiclone. Brotizolam did not affect the morning recall compared to placebo, but subjects remembered less words under zopiclone treatment, suggesting that this drug could affect memory storage during sleep.

REM sleep effects as a biomarker for the effects of antidepressants in healthy volunteers

The potential use of rapid eye movement (REM) sleep effects as a biomarker for the therapeutic effects of antidepressants in healthy volunteers is reviewed. A literature search was performed to select studies investigating the effects of antidepressants on REM sleep. To assess the specificity of REM sleep effects as a biomarker, the effects of other central nervous system drugs on REM sleep were also investigated. A significant REM sleep reduction was shown for 16 of 21 investigated antidepressants after single-dose (mean reduction 34.1%) and for 11/13 drugs after multiple-dose administration (mean reduction 29.2%). The median increase in REM latency was approximatety 60% after single- or multiple-dose administration. REM sleep effects were linearly normalized to therapeutic doses, by dividing the REM sleep effect by the investigated dose and multiplying by the therapeutic dose. Normalized REM sleep effects were highly variable (range -27.0% to 81.8% for REM sleep; range -17.0% to 266.3% for REM latency) and demonstrated no relationship with relevant pharmacological properties of the investigated drugs. No quantifiable dose-response relationship could be constructed after single and multiple dose administration. REM sleep effects were not specific for antidepressants. Benzodiazepines, for example, caused an average dose normalized REM sleep reduction of 8.7% and a median 8.6% increase of REM latency. This review demonstrates that although REM sleep effects occur with most of the antidepressants, it is by itself of limited value as a biomarker for antidepressant action. The specificity for antidepressants is limited, and it does not show a quantitative dose-response relationship to antidepressant agents. This is at least partly due to the complex relationships between drug pharmacokinetics and the variable time course of REM and other sleep stages throughout the night. Models that take these complex relationships into account may provide more comprehensive and quantifiable results.

Alcohol effect on sleep electroencephalography by fast Fourier transformation

The influence of alcohol (ethanol) on sleep was investigated in 10 men. Polysomnography (PS) was recorded on a baseline night (BL-N) and an ethanol (0.8 g/kg) night (Et-N). On visual score rapid eye movement (REM) sleep was reduced, REM latency was prolonged on Et-N as compared to BL-N. Using the fast Fourier transformation method, electroencephalographic power density of REM sleep in delta frequencies band and in the 10-12 Hz range of non-REM sleep were enhanced. REM sleep and non-REM sleep changes were prominent in the second-half and first-half of the night, respectively.

The intermediate stage and paradoxical sleep in the rat: influence of three generations of hypnotics

Paradoxical sleep in the rat, cat and mouse is preceded and sometimes followed by a short-lasting intermediate stage characterized by high-amplitude anterior cortex spindles and low-frequency hippocampal theta rhythm. Several neurophysiological arguments suggest that the intermediate stage corresponds to a brief functional disconnection of the forebrain from the brainstem. This paper is devoted to the review of quantitative and qualitative influences of three generations of hypnotics on the intermediate stage-paradoxical sleep couple. Barbiturates, first-generation hypnotics, extend the intermediate stage at the expense of paradoxical sleep. Three benzodiazepines are compared, two with a short half-life (triazolam and midazolam) and one with a long half-life (diazepam). They also decrease sleep occurrence latency and increase the intermediate stage at the expense of paradoxical sleep, except for midazolam, which increases both the intermediate stage and paradoxical sleep at low dose. Zolpidem and zopiclone, hypnotics of third generation, decrease paradoxical sleep but the intermediate stage never substitutes for paradoxical sleep. The results are discussed in relationship to the functional aspects of this turning-point period of sleep.