Residual and acute effects of flurazepam and triazolam in normal subjects

Update on the safety considerations in the management of insomnia with hypnotics: incorporating modified-release formulations into primary care

OBJECTIVE

From a safety perspective, several issues require assessment when a decision is made to prescribe a sleep medication, including next-day residual effects, the potential for abuse, tolerance, and dependence. This article aims to provide an update of the safety profile of agents commonly used in the management of insomnia, with an emphasis on newly approved hypnotics.

DATA SOURCES

Publications relevant to the subject of this review were identified by a PubMed search (conducted without date restrictions; search terms: insomnia WITH safety OR tolerability OR side effects OR tolerance OR dependence OR abuse OR residual effects AND benzodiazepines OR non-benzodiazepines OR zolpidem OR eszopiclone OR zaleplon OR ramelteon OR melatonin OR trazodone OR antihistamines OR alcohol OR alternative therapies), and additional articles (selected by the author on the basis of his experience) were included.

STUDY SELECTION AND DATA EXTRACTION

Publications relevant to the objective of this article were obtained, and the key safety data relating to adverse events, next-day residual effects, tolerance, and withdrawal were summarized.

DATA SYNTHESIS

The non-benzodiazepines (eszopiclone, zolpidem, zolpidem extended-release, and zaleplon), which have largely replaced the benzodiazepines for insomnia treatment, have a lower risk of tolerance, dependence, abuse, and residual effects compared with benzodiazepines. The modified-release formulation of zolpidem demonstrates a comparable safety profile to that of original zolpidem but has an additional sleep maintenance benefit. Ramelteon, a novel melatonin receptor agonist, is indicated for sleep-onset difficulties and is not scheduled. Over-the-counter agents, alternative therapies, and the prescription of off-label drugs, such as trazodone, have a lack of controlled clinical efficacy and safety studies in the treatment of insomnia and as a result should be used with caution.

CONCLUSIONS

Overall, published studies report that the safety of insomnia treatments has improved considerably over the past 10 years with the introduction of agents that provide improved safety, particularly with regard to next-day residual effects and abuse liability.

Treatment options for insomnia--pharmacodynamics of zolpidem extended-release to benefit next-day performance

BACKGROUND

Insomnia can manifest as difficulty in falling asleep, in maintaining sleep throughout the night, or waking up too early, with symptoms often unpredictably changing over time. Pharmacologic options for insomnia treatment include prescription hypnotics, such as gamma-amino butyric acid-receptor agonists, sedating antidepressants, over-the-counter antihistamines, melatonin-receptor agonists, and alternative therapies. A concern with insomnia medications is the risk of next-day residual effects, which can impair memory and ability to perform certain tasks, such as driving, and may increase the risk of accidents and falls, especially in the elderly.

OBJECTIVES

To describe the impact of current insomnia treatments on next-day performance.

RESULTS

The longer-acting benzodiazepines are associated with next-day "hangover" effects and, as a result, have been largely replaced by agents in the nonbenzodiazepine class, which typically have shorter half-lives. The hypnotic, sedative activities of these classes of drugs depend on variations in binding characteristics to the alpha1 subunit of the gamma-amino butyric acidA-receptor, which inhibits neuronal activity in broad areas of the brain and is found in areas of the brain responsible for sleep/wakefulness and sedation. However, nonbenzodiazepines with a rapid onset of action and short half-life have shown limited efficacy for maintaining sleep throughout the night. These properties have contributed to the development of modified-release formulations. Zolpidem extended-release is a bilayer tablet that retains the fast onset of action of its parent compound zolpidem while extending the duration of hypnotic activity, owing to a slower-release portion of the tablet.

CONCLUSIONS

Based on clinical evidence, the risk of residual next-day effects of zolpidem extended-release is limited, mainly due to the similarly short half-life in its extended-release formulation.

Effect of repeated gaboxadol administration on night sleep and next-day performance in healthy elderly subjects

Aging is associated with dramatic reductions in sleep continuity and sleep intensity. Since gaboxadol, a selective GABA(A) receptor agonist, has been demonstrated to improve sleep consolidation and promote deep sleep, it may be an effective hypnotic, particularly for elderly patients with insomnia. In the present study, we investigated the effects of subchronic gaboxadol administration on nocturnal sleep and its residual effects during the next days in elderly subjects. This was a randomized, double-blind, placebo-controlled, balanced crossover study in 10 healthy elderly subjects without sleep complaints. The subjects were administered either placebo or 15 mg gaboxadol hydrochloride at bedtime on three consecutive nights. Sleep was recorded during each night from 2300 to 0700 h and tests assessing attention (target detection, stroop test) and memory function (visual form recognition, immediate word recall, digit span) were applied at 0900, 1400, and 1700 h during the following days. Compared with placebo, gaboxadol significantly shortened subjective sleep onset latency and increased self-rated sleep intensity and quality. Polysomnographic recordings showed that it significantly decreased the number of awakenings, the amount of intermittent wakefulness, and stage 1, and increased slow wave sleep and stage 2. These effects were stable over the three nights. None of the subjects reported side effects. Next-day cognitive performance was not affected by gaboxadol. Gaboxadol persistently improved subjective and objective sleep quality and was devoid of residual effects. Thus, at the employed dose, it seems an effective hypnotic in elderly subjects.

Flunitrazepam-induced changes in neurophysiological, behavioural, and subjective measures used to assess sedation

INTRODUCTION

Certain features of event-related potentials (ERPs), electroencephalographic (EEG), and behavioural measures vary with differing states of alertness and/or sedation.

PURPOSE

This study was conducted to investigate changes in several measures usually viewed as reflecting states of sedation/sleepiness associated with the use of a range of doses of the hypnotic benzodiazepine (BZD) flunitrazepam (FNZ).

METHODS

This was a double blind, independent group design study of the effects of acute oral doses of FNZ in young healthy volunteers. Forty-eight subjects were randomly allocated to one of four groups-FNZ (0.6, 0.8, and 1.0 mg) and placebo (PLAC)-and tested prior to treatment and then in a posttreatment session close to the theoretical peak plasma concentration. ERP latencies and amplitudes were measured at midfrontal (Fz), midcentral (Cz), and midparietal (Pz) using a standard auditory oddball paradigm. EEG changes were assessed at Pz. Behavioural measures included the digit-symbol substitution test (DSST), a cancellation task (CT), and subjective ratings of alertness and attentiveness by the subjects (SUB) and the experimenter (EXP).

RESULTS

FNZ led to psychomotor impairments and decreased alertness and attention; these effects were consistent with previous findings. A progressive, dose-related increase in P3 latency occurred in Fz, Cz, and Pz, and there was an increase in N1 (Fz, Cz) and N2 (Fz). N2-P3 amplitude decreased in Fz. EEG power bands beta 1 increased for the two highest doses, but no significant differences were noted in theta, delta, and alpha bands. P3 latencies, experimenter-rated levels of alertness, and DSST scores differentiated all three doses of FNZ from PLAC.

CONCLUSION

The most sensitive measures used were P3 latencies of the ERPs (which varied with FNZ dose), DSST, and the experimenter-rated levels of alertness. However, we found no evidence for the assumption that one single phenomenon was reflected in all measures and different mechanisms were probably involved. Further experiments will be needed for more in-depth probing of the finer mechanisms underlying sedation/sleepiness and how they affect behavioural and eletrophysiological measures of the central nervous system (CNS) function.

Pharmacodynamic profile of Zaleplon, a new non-benzodiazepine hypnotic agent

The challenge in developing hypnotic agents for the treatment of insomnia is to balance the sedative effect needed at bedtime with the residual sedation on awakening. Zaleplon is a novel pyrazolopyrimidine hypnotic agent that acts as a selective agonist to the brain omega(1) receptor situated on the alpha(1) subunit of the GABA(A) receptor complex. Zaleplon was proven to be an effective hypnotic drug as it consistently and significantly reduced latency to persistent sleep in insomniac patients for doses of 10 mg and above in polysomnography studies. The pharmacodynamic profile of zaleplon on psychomotor performance, actual driving and cognitive function, including memory, was assessed in several randomized, double-blind, placebo-controlled studies in healthy young subjects as well as insomniac patients by using various positive controls (zolpidem, zopiclone, triazolam and flurazepam). The recommended hypnotic dose of zaleplon in young adults (10 mg) produced minimal or no impairment of psychomotor and memory performance even when administered during the night as little as 1 h before waking. No impairment of actual driving was observed when zaleplon 10 mg was administered either at bedtime or in the middle of the night as little as 4 h before waking. Zaleplon 20 mg, twice the recommended dose, generally produced significant impairment of performance and cognitive functions when these functions were measured at the time of peak plasma concentration, i.e. 1 h after dose administration, and no impairment of driving abilities was observed 4 h after a middle-of-the-night administration. In contrast, consistent detrimental residual effects on various aspects of psychomotor and cognitive functions were observed with the therapeutic doses of the various commonly prescribed hypnotic agents used as comparators, e.g. zolpidem 10 mg up to 5 h after dose administration, zopiclone 7.5 mg up to 10 h after, flurazepam 30 mg up to 14 h after and triazolam 0.25 mg up to 6 h after. Also, zolpidem 10 mg and zopiclone 7.5 mg were also shown to significantly impair driving ability the next morning when this was measured 4 h and up to 10 h after dose administration, respectively. The present review shows that zaleplon 10 mg has little or no residual effect when administered in the middle of the night, as late as 1 h before waking, and is devoid of impairment of driving abilities as assessed by actual driving 4 h after dose administration. The lack of clinically significant or minimally statistically significant residual effects of zaleplon even at its peak concentration may be explained by its unique pharmacokinetic (rapid elimination half-life) and pharmacodynamic (low affinity, and specific binding profile to various subunits of the GABA(A)receptor) profiles. These properties allow zaleplon to be used for treatment of symptoms only when they occur, either at bedtime or later in the night, without incurring significant risk of developing next-day impairment of psychomotor and cognitive functioning. Copyright 2001 John Wiley & Sons, Ltd.

Benzodiazepine pharmacodynamics: evidence for biophase rate limiting mechanisms

Pharmacokinetics do not adequately reflect recovery from cognitive neuromotor impairment induced by most benzodiazepines. This paper examines across time the nature of the relationship of effect to serum concentration of three benzodiazepines. Using the same protocol lorazepam, alprazolam, diazepam and placebo were administered to eight healthy males at doses of 0.057, 0.029, 0.286 and 0.000 mg/kg, body weight, respectively for the first study and at 0.028, 0.014, 0.143 and 0.000 mg/kg, respectively, for the second study. After each dose administration multiple measurements were made over a period of 5.5-11.5 h using two different psychomotor performance tests. Serum drug concentrations were also measured. The profiles for diazepam and alprazolam effects demonstrate a stepwise decrement in the slopes of the concentration versus response curves across time, illustrating the rapid development of acute tolerance. In contrast, lorazepam induced a remarkably constant relationship between concentration and effect across testing intervals.

Study of the potential reversal of triazolam memory and cognitive deficits by RU 41 656 in healthy subjects

The potential antagonism of a single oral dose of RU 41 656 (10 mg) on the memory and attention disturbances induced by oral administration of triazolam (0.25 mg) have been investigated in a 3-period, placebo controlled, double blind, cross-over study involving 12 healthy young volunteers. The effects of the compounds were evaluated by objective tests (Buschke selective reminding test, CFF, simple reaction time, tapping, arithmetical calculation) and subjective measurements (visual analogue scale, side effects questionnaire). Measurements were taken before treatment and 2, 4 and 7 h after RU 41 656 intake. Triazolam caused anterograde amnesia as already described with other benzodiazepine with few sedative effects at this dosage. Under the experimental conditions of the trial, RU 41 656 failed to counteract the memory deficits induced by triazolam.

Benzodiazepines and caffeine: effect on daytime sleepiness, performance, and mood

In a double-blind parallel group design, 80 young adult males were divided into eight treatment groups. Subjects received 15 or 30 mg flurazepam, 0.25 or 0.50 mg triazolam, or placebo at bedtime, and 250 mg caffeine or placebo in the morning for 2 treatment days. Two objective (Multiple Sleep Latency Test and lapses) and two subjective (Stanford Sleepiness Scale and Visual Analog Scale) measures of sleepiness, five performance tests, and two mood measures (Profile of Mood Scale and Visual Analog Mood Scale) were administered repeatedly on both days. Significant treatment effects were found for sleepiness but not for performance or mood. Early morning caffeine significantly antagonized next day hypnotic-induced drowsiness and enhanced alertness in the subjects who received bed-time placebo. Flurazepam, 30 mg, subjects were more sleepy than all other groups. Although not significantly different, the flurazepam, 30 mg, group demonstrated a trend toward poorer performance and a more negative mood than all other groups. Caffeine most improved performance of this group. In all groups, sleepiness was greatest and performance and mood poorest in early morning trials and caffeine was most effective at this time.

Acute reversal of flunitrazepam effects by Ro 15-1788 and Ro 15-3505: inverse agonism, tolerance, and rebound

A phase 1 double blind crossover comparison of a new benzodiazepine antagonist (Ro 15-3505) with Ro 15-1788 and placebo, in the reversal of sedative and psychophysiological effects of single IV doses of flunitrazepam (2 mg), was carried out in 12 normal volunteers. The antagonists were equally effective, leading to full reversal of all effects with a potency ratio of approximately 2.5 mg Ro 15-1788 for 1 mg Ro 15-3505. Inverse agonism, in the form of unpleasant feelings and symptoms, was reported by all subjects following Ro 15-3505 but none after Ro 15-1788. Adaptational phenomena such as acute tolerance and rebound of sedative effects of flunitrazepam were also detected and their potential implications are discussed.

Assessment of the effects of drugs on memory

This survey is based on 70 controlled investigations of the effects of drugs on memory in healthy volunteers. Although detracting effects were predominant, enhancements were reported as well. The effects of 29 well-known drugs on 15 familiar tests are summarized in a way that permits comparisons of the effects of different drugs and of test sensitivities. There is a discussion of factors that could bias or obscure investigations of the effects of drugs on learning and remembering.

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)