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The interaction between zolpidem and beta-CMC: a clue to the identification of receptor sites involved in the sedative effect of zolpidem.

The interaction of beta-CMC, an amino beta-carboline recently described as a selective antagonist of the sedative effect of diazepam, with zolpidem, an imidazopyridine hypnotic, which like beta-CMC binds preferentially to the omega 1 (BZ-1) site of the GABA benzodiazepine chloride channel receptor complex, was investigated. In mice, beta-CMC antagonized the effect of zolpidem against isoniazid-induced convulsions without affecting its activity against convulsions induced by pentylenetetrazole or electroshock. beta-CMC also antagonized the decrease in locomotor activity and the impairment in muscle strength provoked by zolpidem. In rats trained to discriminate zolpidem, beta-CMC antagonized both the interoceptive stimulus and the decrease in the rate of lever pressing produced by zolpidem. This selective antagonism, inhibition of effects of zolpidem exerted by low doses (locomotor activity and isoniazid-induced convulsions) as well as effects produced by high doses (muscle strength) but not those provoked by intermediate doses (pentylenetetrazole and electroshock-induced convulsions), could not be explained by a receptor occupancy hypothesis. These results suggest that the anticonvulsant and sedative effects of zolpidem do not involve the same receptor subtype and that the hypnoselective properties of zolpidem may be linked to its selectivity for the omega 1 (BZ-1) site of the GABAA receptor.

Animals

In vivo interaction of zolpidem with central benzodiazepine (BZD) binding sites (as labeled by [3H]Ro 15-1788) in the mouse brain. Preferential affinity of zolpidem for the omega 1 (BZD1) subtype.

Zolpidem is a novel hypnotic drug which possesses preferential affinity, under in vitro conditions, for the omega 1 (BZD1) subtype of BZD binding sites. In the present study the in vivo interaction of zolpidem with mouse brain BZD binding sites, as labeled by i.v. injection of [3H]Ro 15-1788, has been investigated. Intraperitoneal administration of zolpidem (30 min before sacrifice) decreased in a dose-dependent manner, the retention of [3H]Ro 15-1788 in the cerebral cortex (ED50 = 8.9 mg/kg i.p.); the inhibition by zolpidem was maximal (70%) at 5 to 10 min postinjection and of only 10% 1 hr later. These kinetics are in agreement with its short lasting hypnotic properties. CGS 9896, CL 218,872 and flunitrazepam also prevented the cortical accumulation of [3H]Ro 15-1788 with ED50 values of 12.5, 24 and 0.17 mg/kg i.p., respectively. Zolpidem, like flunitrazepam, diminishes exploratory activity and possesses anticonvulsant and myorelaxant effects in the mouse. However, in contrast to flunitrazepam, the sedative action of zolpidem can be evidenced at a much lower recognition site occupancy (35%) than that needed for myorelaxant or anticonvulsant effects (50-56%). The regional selectivity of zolpidem as an inhibitor of [3H]Ro 15-1788 in vitro and in vivo binding in the mouse brain has been assessed by quantitative autoradiography.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals

Distribution of [3H]zolpidem binding sites in relation to messenger RNA encoding the alpha 1, beta 2 and gamma 2 subunits of GABAA receptors in rat brain.

Localization of the messenger RNAs that encode the alpha 1, beta 2 and gamma 2 subunits of GABAA showed a distinct topographic pattern in rat brain which corresponded with [3H]zolpidem binding in most brain regions. The close topographic correspondence between the specific receptor subunits examined and the distribution of [3H]zolpidem binding sites provides support for the hypothesis that this benzodiazepine type 1 selective ligand binds to a GABAA receptor that consists of alpha 1, beta 2 and gamma 2 subunits in the rat brain. Brain regions with relatively high densities of alpha 1, beta 2 and gamma 2 subunits of GABAA and [3H]zolpidem binding included olfactory bulb, medial septum, ventral pallidum, diagonal band, inferior colliculus, substantia nigra pars reticulata and specific layers of the cortex. Two areas with low [3H]zolpidem binding and a virtual absence of these GABAA receptor subunit messenger RNAs were the lateral septum and the striatum. In contrast to the discrete pattern observed for alpha 1 and beta 2 subunit messenger RNAs, the gamma 2 subunit messenger RNA was distributed more diffusely in brain. Only the hippocampus, layer 2 of the piriform cortex and the cerebellum showed a strong concentration of the gamma 2 subunit messenger RNA. It was determined with a polymerase chain reaction assay that both long and short variants of the gamma 2 subunit messenger RNAs were present within several of the brain sites selected for examination. Sites with high densities of [3H]zolpidem binding sites had a greater relative abundance of the gamma 2 long splice variant, compared to the gamma 2 short variant. There were some regions that expressed high levels of alpha 1, beta 2 and gamma 2S subunit messenger RNAs but low [3H]zolpidem binding, suggesting that gamma 2 splice variant expression may modulate high-affinity [3H]zolpidem binding. To determine relationships between in vitro [3H]zolpidem binding and functional sensitivity in vivo, interactions between zolpidem and GABA were assessed in brain regions that contained high and low densities of [3H]zolpidem binding sites. In the medial septum, a brain region with a high concentration of [3H]zolpidem binding sites, iontophoretic application of zolpidem enhanced the inhibitory effect of GABA responses on 70% of the neurons examined. In the lateral septum, which contains very low densities of [3H]zolpidem binding sites, neurons were not sensitive to zolpidem enhancement of GABA-induced inhibition. These electrophysiological results demonstrate a correspondence between the regional distribution of [3H]zolpidem binding in vitro and functional sensitivity to the drug in vivo.

Animals

Effect of zolpidem on gamma-aminobutyric acid (GABA)-induced inhibition predicts the interaction of ethanol with GABA on individual neurons in several rat brain regions.

Previous investigations have suggested a relationship between zolpidem binding within specific brain regions and the ability of ethanol or zolpidem to enhance gamma-aminobutyric acid (GABA)-induced inhibition. The purpose of the present study was to extend our electrophysiological analysis to additional brain sites with high levels of zolpidem binding. In the brain regions chosen, red nucleus and globus pallidus, GABA-induced inhibition was shown to be enhanced by either ethanol or zolpidem on some, but not all, neurons. These findings led to the hypothesis that the effect of zolpidem on GABA-induced inhibition would predict the action of ethanol on responses to GABA for that neuron. When zolpidem and ethanol were applied individually to the same neurons in the red nucleus and globus pallidus, those neurons sensitive to zolpidem enhancement of GABA also were sensitive to ethanol. Conversely, if zolpidem did not enhance responses to GABA, ethanol did not enhance responses to GABA at these brain sites. A similar relationship between the abilities of zolpidem and ethanol to enhance GABA-induced inhibition was obtained in 90% of the neurons studied in the medial septum/diagonal band and ventral pallidum. These studies provide further support for the contention that the zolpidem-sensitive GABAA-benzodiazepine isoreceptor also responds to ethanol. Finally, the expression of GABAA subunit mRNAs was analyzed by polymerase chain reaction from micropunches of several brain regions that contain zolpidem binding sites and exhibit sensitivity to ethanol. Polymerase chain reaction analysis proved more sensitive than in situ hybridization in the detection of receptor subunit mRNAs. Several subunits (alpha 1, alpha 2, alpha 3, beta 2, beta 3 and gamma 2) were common to all brain regions in which ethanol and zolpidem enhanced GABA responses. GABAA receptor alpha 4/5, alpha 6, beta 1, gamma 1, gamma 3 and delta subunits were not consistently expressed in association with the presence of zolpidem binding. These data are consistent with the view that one native GABAA receptor to which zolpidem binds, and on which ethanol acts, contains the GABAA receptor subunits alpha 1, beta 2 and gamma 2; however, the present investigation did not preclude the possibility that other subunit combinations can contribute to ethanol and zolpidem enhancement of responses to GABA.

Animals

A multicenter, placebo-controlled study evaluating zolpidem in the treatment of chronic insomnia.

BACKGROUND: Zolpidem is a short-acting, nonbenzodiazepine hypnotic with rapid onset of action. Even though it is not a benzodiazepine, it binds to one of three types of central benzodiazepine receptors, showing selective binding to the type 1 benzodiazepine receptor subtype. Therapeutic hypnotic dosages do not disturb normal sleep patterns (sleep architecture). METHOD: A randomized, double-blind, placebo-controlled, parallel group multicenter trial was conducted to determine the effectiveness of 10 mg and 15 mg of zolpidem in the long-term (35 nights) treatment of chronic insomnia in 75 patients. Sleep stage effects and motor and cognitive effects during the 35-night treatment period and the 3-night posttreatment period were also investigated. RESULTS: Within the first week of treatment, 10 mg of zolpidem had a significant effect on latency to persistent sleep and sleep efficiency. Efficacy was maintained throughout the 35 nights of drug administration. There was no evidence of residual effect with 10 mg of zolpidem. Stage 3-4 sleep was preserved at both the 10-mg and 15-mg zolpidem dosages. There was no evidence of tolerance at either dose and no significant treatment differences between the 10-mg zolpidem group and placebo in latency to persistent sleep or sleep efficiency during the posttreatment period. Also, the 10-mg zolpidem dosage was judged by the patients to have helped them fall asleep. Similar results were observed with the 15-mg zolpidem dosage. However, there were significant decreases in REM sleep at Weeks 3 and 4 with 15 mg of zolpidem compared with placebo. Overall, incidence rates of treatment-emergent adverse events in the zolpidem groups were similar to those in the placebo group. CONCLUSION: This is the first sleep laboratory study using a parallel placebo group to demonstrate efficacy for longer than 4 weeks with a hypnotic agent. In this study 10 mg of zolpidem was found to be safe and effective for the long-term treatment of chronic insomnia, demonstrating hypnotic efficacy without affecting sleep stages or producing tolerance effects, rebound effects, or detrimental effects on psychomotor performance. The 15-mg zolpidem dosage provided no clinical advantage over the 10-mg zolpidem dosage.

Adult

Zolpidem and triazolam in humans: behavioral and subjective effects and abuse liability.

Zolpidem, which is currently marketed in Europe as a hypnotic, is a short-duration imidazopyridine whose actions are mediated at the gamma-aminobutyric acid benzodiazepine receptor complex. However, zolpidem produces a variety of biochemical differences from classic benzodiazepine agonists including showing selectivity for the central BZ1 (omega 1) receptor subtype as well as showing a different pattern of distribution of binding sites. This study compared zolpidem to the benzodiazepine hypnotic triazolam in 15 healthy male volunteers with histories of sedative drug abuse. Placebo, zolpidem (15, 30 and 45 mg) and triazolam (0.25, 0.5 and 0.75 mg) were administered p.o. in a mixed sequence in a double-blind, cross-over design. The onset time with zolpidem was faster than with triazolam, with peak effects of both drugs occurring at 1 to 2 hr after administration. Both zolpidem and triazolam produced dose-related decrements in performance on various performance tasks including circular lights, reaction time, balance, number recall and the digit symbol substitution test. Both drugs also produced similar dose-related changes on various observer ratings including overall strength of drug effect. Triazolam, but not zolpidem, increased subject- and observer-rated sleepiness and produced greater impairment on a picture memory task. Zolpidem, but not triazolam, produced increases in subject ratings of various somatic symptoms (e.g., dizzy, anxious and queasy) and there were 9 days on which subjects vomited after zolpidem, but none after triazolam. Although the highest dose of both drugs was identified by subjects as being active, the highest dose of triazolam was identified as being barbiturate, benzodiazepine or alcohol, almost twice as often as the highest dose of zolpidem. Overall, this study shows that although zolpidem produces many effects in common with triazolam, it also has a unique profile of effects distinguishable from classic benzodiazepine agonists. The mechanism(s) underlying these differences is unclear, but may be related to the atypical biochemical profile of zolpidem.

Adult

Zolpidem, a novel nonbenzodiazepine hypnotic. I. Neuropharmacological and behavioral effects.

Zolpidem [N,N,6-trimethyl-2-(4-methylphenyl)imidazo[1,2-a]pyridine-3-acetamide hemitartrate] is reported to be a rapid onset, short duration hypnotic that interacts at the benzodiazepine recognition site. The present report establishes the neuropsychopharmacological profile of zolpidem and compares it with those of benzodiazepine hypnotics. Although in mice the effects of zolpidem are qualitatively similar to those of midazolam, triazolam and flunitrazepam, sedation with zolpidem occurs at doses 10 and 20 times lower than those inducing anticonvulsant and myorelaxant effects, respectively. In contrast, the benzodiazepines studied induce sedation at doses causing myorelaxation and which are 2 to 6 times superior to those antagonizing pentetrazole-induced convulsions. In the rat, zolpidem induces sleep (as indicated behaviorally and electrocorticographically) and displays anticonflict activity in a punished drinking paradigm, as do the benzodiazepines. However, whereas benzodiazepine hypnotics induce EEG sleep patterns in curarized rats at doses similar or inferior to those active in the conflict test (in freely moving animals), the hypnotic effect of zolpidem is seen at doses 10 times lower than those producing an anticonflict effect. Moreover, a qualitative difference between the effects of zolpidem and benzodiazepines is observed in electrocorticographic recordings obtained in curarized rats: electrocorticographic hypersynchronization induced by zolpidem is dominated by the energy increase within the 2 to 4 Hz band whereas the benzodiazepines increase predominantly energy levels within the 12 to 14 Hz band. Studies of the sleep-wakefulness cycle in the rat and the cat revealed that hypnotic doses of zolpidem do not alter the pattern of physiological sleep, although elevated doses of the drug decrease paradoxical sleep and increase slow wave sleep. In rats trained to discriminate chlordiazepoxide, zolpidem fails to generalize with the chlordiazepoxide-associated lever indicating that the compound and benzodiazepines do not share the same discriminative stimulus properties. Nevertheless, the anticonvulsant, hypnotic, myorelaxant and anticonflict effects of zolpidem are antagonized by benzodiazepine receptor antagonist Ro 15-1788 and CGS 8216 indicating an involvement of the benzodiazepine recognition site in the action of this drug. The highly selective sedative effect of zolpidem (as compared to myorelaxant and anticonvulsant effects) suggests that it may possess a specificity for certain subtypes of benzodiazepine receptors.

Animals

High affinity [3H]zolpidem binding in the rat brain: an imidazopyridine with agonist properties at central benzodiazepine receptors.

[3H]Zolpidem, a novel hypnotic drug possessing a chemical structure unrelated to that of benzodiazepine (BZD) was employed as a new ligand to determine its binding characteristics to membrane preparations of rat cerebral cortex and cerebellum. In both structures, the imidazopyridine [3H]zolpidem bound with high affinity to a single population of recognition sites. The cerebellum possessed a similar number of [3H]zolpidem and [3H]diazepam binding sites, while the cerebral cortex possessed a lower density of [3H]zolpidem than [3H]diazepam binding sites. In contrast to [3H]diazepam binding, [3H]zolpidem binding was not detectable in the spinal cord. In the cortex, BZDs had a similar potency to displace [3H]zolpidem and [3H]diazepam binding while non-BZDs were more potent to inhibit [3H] zolpidem binding than [3H]diazepam binding. The binding of [3H]zolpidem was enhanced by GABA to the same extent as [3H]diazepam binding. The increase in [3H] zolpidem binding caused by chloride ions was less pronounced than that in [3H]diazepam binding. It is concluded that [3H]zolpidem possesses selectivity for BZD receptors with the pharmacological characteristics and regional distribution of the BZD1 receptor subtype. [3H]Zolpidem as a radioligand offers a useful additional tool to study the mechanism of action of hypnotics acting through BZD receptor subtypes.

Animals

[Contribution of zolpidem in the management of sleep disorders].

Zolpidem is a nonbenzodiazepine hypnotic agent belonging to a new class of psychotropic drugs the imidazopyridines which enhance the GABAA receptor function by interacting with a specific receptor population. Zolpidem binds selectively to the Omega-1 receptor subtype and from a pharmacological point of view differs from benzodiazepines (BZD) by producing a strong sedative and hypnotic profile which predominates over the anticonvulsivant and anxiolytic activity and moreover appears practically devoid of myorelaxant properties. From a pharmacodynamic point of view, these results suggest that zolpidem facilitates more selectively than BZD, GABAA function and produces a selective hypnotic effect. Though if the role played by receptors in tolerance and dependence has not been yet fully elucidated, it could be described as an adaptative process to sustained stimulation of GABA function. Animal data obtained with zolpidem differs substantially from that of the BZD and indicates that repeated zolpidem administration may not lead to phenomena of tolerance and withdrawal syndrome after abrupt drug discontinuation. In human following oral intake, zolpidem is very rapidly (Tmax: 30-40 min) absorbed. The clearance is essentially metabolic and less than 1% is recovered in urine. The apparent plasma half-life is of 2.0-2.5 hours in most adult subjects and metabolites are totally inactive. The hypnotic activity of zolpidem and its effects on sleep architecture have been assessed in polysomnographic studies: 11 studies in 579 healthy volunteers and 12 studies in 202 insomniac patients. From all the patient studies, it emerges clearly that zolpidem at the dose of 10 mg significantly decreases sleep onset latency, the number and the duration of nocturnal awakenings, and concomitantly increases total sleep time. Furthermore, at variance with what observed with reference benzodiazepine hypnotics, zolpidem does not alter patient sleep architecture: it increases only moderately stage 2, it increases, when reduced, stages 3 and 4 (slow wave sleep) and it does not decrease REM sleep. Clinical studies conducted on more than 4,000 insomniac patients have clearly shown that at the dose of 10-20 mg, zolpidem induces from the first night a definite hypnotic effect in all types of insomnia. In elderly subjects an initial dose of 5 mg should be considered. The possible presence of residual effects during the day following administration of zolpidem has been assessed in 535 healthy volunteers and in 133 insomniac patients according to a double blind (versus placebo and/or benzodiazepine) controlled design.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult

Pharmacokinetics, brain distribution and pharmaco-electrocorticographic profile of zolpidem, a new hypnotic, in the rat.

Zolpidem [N,N-6-trimethyl-2-(4-methylphenyl)imidazo[1,2-a]pyridine-3- acetamide] administered as the hemitartrate salt has proven to be an effective hypnotic agent in animals and humans. This study describes the pharmacokinetic behavior of zolpidem in plasma and brain of rat after i.v. and p.o. administration of 2.63 mg.kg-1 of [14C]zolpidem (dose expressed as the base). Autoradiography was used to examine the regional distribution of the compound and the metabolic profile of zolpidem in the plasma and brain was also investigated. The pharmacokinetic data were related to electrocorticogram power spectral analysis. After i.v. administration, the disappearance of zolpidem from plasma fitted a biexponential model with a rapid phase of 0.2 to 0.3 hr and a slower phase of 1.3 to 1.5 hr. After p.o. dosing, peak plasma concentrations where already attained at 15 min (first sampling time). Independent of the route of administration, the concentrations of zolpidem in the brain at shorter times were 30 to 50% those of the plasma values. Furthermore, up to 1 hr, zolpidem accounted for 80 to 90% of brain radioactivity. The rate of disappearance from brain paralleled that from plasma. Autoradiographic studies confirmed the rapid absorption and elimination of zolpidem as well as the relatively homogenous distribution throughout the brain. Electrocorticogram analysis in immobilized rats after i.v. administration of zolpidem showed a rapid onset and a short-acting sedative effect compatible with the kinetic profile of the parent compound. Metabolites of zolpidem displayed a poor penetration into the brain and no significant hypnotic activity. At the dose of zolpidem used, no alteration of the sleep pattern was observed.

Animals

The acute effects of zolpidem, administered alone and with alcohol, on cognitive and psychomotor function.

BACKGROUND: Skills performance impairment after acute doses of zolpidem (a short-acting, nonbenzodiazepine hypnotic), alone and with alcohol, was evaluated in 24 subjects. The study was designed to test whether the effects of zolpidem and alcohol are simply additive or reflect potentiation. METHOD: Healthy male volunteers participated in a randomized, six-way crossover study of placebo, zolpidem 10 mg, or zolpidem 15 mg in combination with a placebo beverage or an alcohol dose selected to attain a peak blood alcohol concentration of 0.08% (drug administered double-blind; beverages administered single-blind). A laboratory test battery of four tasks measured concurrent information processing ability (divided attention task), information processing rate (visual backward masking task), immediate memory (Sternberg task), and sustained attention (vigilance task). The battery was repeated three times to measure peak (+45 minutes), postpeak (+130 minutes), and residual (+230 minutes) treatment effects after each dosing. RESULTS: Performance on each test-battery task was significantly impaired (p < .05) by both alcohol and zolpidem (combined and each given alone) during the peak-effect assessment. Residual effects were not observed, with the exception of significant alcohol and drug effects on divided attention performance (p < .05). Analysis of variance tests revealed significant main effects of alcohol and zolpidem, but no significant alcohol-by-drug interactions were found for any measure of skills performance. In general, additive effects of alcohol were detected with zolpidem 10 mg but not with zolpidem 15 mg. CONCLUSION: Although some additive effects of alcohol on performance skills were seen with the lower 10-mg dose of zolpidem, no nonadditive effects were found. That is, alcohol does not appear to potentiate the effects of zolpidem on the various performance skills tested in this population and at the doses and times evaluated. With the exception of persisting deficits (at 4 hours postdose) on the more demanding divided attention task, all other findings were consistent with evidence that zolpidem is a short-acting hypnotic drug.

Adult

Autoradiographic localization of [3H]zolpidem binding sites in the rat CNS: comparison with the distribution of [3H]flunitrazepam binding sites.

The regional distribution of [3H]zolpidem, a novel imidazopyridine hypnotic possessing preferential affinity for the BZD1 (benzodiazepine subtype 1) receptor, has been studied autoradiographically in the rat CNS and compared with that of [3H]flunitrazepam. The binding of [3H]zolpidem to rat brain sections was saturable, specific, reversible, and of high affinity (KD = 6.4 nM). It occurred at a single population of sites whose pharmacological characteristics were similar to those of the benzodiazepine receptors labeled with [3H]flunitrazepam. However, ethyl-beta-carboline-3-carboxylate and CL 218,872 were more potent displacers of [3H]zolpidem than of [3H]flunitrazepam. The autoradiographic brain distribution of [3H]zolpidem binding sites was qualitatively similar to that previously reported for benzodiazepine receptors. The highest levels of [3H]-zolpidem binding sites occurred in the olfactory bulb (glomerular layer), inferior colliculus, ventral pallidum, nucleus of the diagonal band of Broca, cerebral cortex (layer IV), medial septum, islands of Calleja, subthalamic nucleus, and substantia nigra pars reticulata, whereas the lowest densities were found in parts of the thalamus, pons, and medulla. Comparative quantitative autoradiographic analysis of the binding of [3H]zolpidem and [3H]flunitrazepam [a mixed BZD1/BZD2 (benzodiazepine subtype 2) receptor agonist] in the CNS revealed that the relative density of both 3H-labeled ligands differed in several brain areas. Similar levels of binding for both ligands were found in brain regions enriched in BZD1 receptors, e.g., substantia nigra pars reticulata, inferior colliculus, cerebellum, and cerebral cortex lamina IV. The levels of [3H]zolpidem binding were five times lower than those of [3H]flunitrazepam binding in those brain regions enriched in BZD2 receptors, e.g., nucleus accumbens, dentate gyrus, and striatum. Moreover, [3H]zolpidem binding was undetectable in the spinal cord (which contains predominantly BZD2 receptors). Finally, like CL 218,872 and ethyl-beta-carboline-3-carboxylate, zolpidem was a more potent displacer of [3H]flunitrazepam binding in brain regions enriched in BZD1 receptors than in brain areas enriched in BZD2 receptors. The present data add further support to the view that zolpidem, although structurally unrelated to the benzodiazepines, binds to the benzodiazepine receptor and possesses selectivity for the BZD1 receptor subtype.

Animals

A double-blind, comparative study of zolpidem and placebo in the treatment of insomnia in elderly psychiatric in-patients.

The efficacy and tolerability of the imidazopyridine hypnotic, zolpidem, were investigated in 119 elderly psychiatric in-patients complaining of insomnia in a double-blind, parallel-group, placebo-controlled trial. After a 7-day placebo washout period, patients were randomized to receive 10 or 20 mg/day zolpidem, or placebo for 21 days; thereafter, all patients received placebo for 7 days. Sleep was assessed by patient observation on days 0, 1, 7, 14, 21, 22 and 28. Compared with placebo, 20 mg/day zolpidem significantly improved total duration of sleep between day 0 and day 21, and this was maintained at day 28. After 10 or 20 mg/day zolpidem, there was also a trend towards improvement in all other sleep parameters, which remained above baseline at day 28. Zolpidem was well tolerated with no withdrawal symptoms during the second 7-day placebo treatment period. Daytime drowsiness was reported in three patients receiving 20 mg/day zolpidem and in one receiving 10 mg/day zolpidem, but there was no significant increase in daytime drowsiness between days 0 and 21. Ataxia occurred in two, one and one patient, respectively, treated with 20 mg/day zolpidem, 10 mg/day zolpidem and placebo. The incidences of other adverse events or effects on clinical and laboratory parameters were minimal and similar in all three treatment groups. It is concluded that, in elderly psychiatric patients, 10 mg/day zolpidem can be used to treat insomnia and can be safely added to concomitant psychotropic treatment without inducing daytime drowsiness.

Aged

Pilot controlled double-blind study of the hypnotic effects of zolpidem in patients with chronic 'learned' insomnia: psychometric and polysomnographic evaluation.

In a pilot double-blind trial in 21 patients with learned or idiopathic insomnia (DSM-IIIR), patients received placebo for 1 week (nights 1-7), either active (zolpidem, 10 mg) or placebo treatment for 2 weeks (nights 8-21) and then placebo for a further week (nights 22-28). Variables to measure efficacy, rebound and withdrawal were assessed daily from day 1 to day 28. Polysomnographic recordings together with sleep cycle analysis were performed on nights 7, 21 and 28. Patients treated with 10 mg zolpidem for 2 weeks had significantly improved sleep efficiency at the end of the randomised double-blind phase compared with the placebo group. Fractionated sleep-cycle analysis showed an increase in slow-wave sleep during the first 2-hour cycle after sleep onset. During the withdrawal placebo week, most of the main sleep variables remained relatively stable in the zolpidem group (nights 22-28), and deteriorated further in the placebo group. At the end of the withdrawal phase, there was a statistically significant difference between groups, in favour of the zolpidem treatment, in sleep efficiency, total sleep time, absolute and percentage of time awake, and percentage of REM sleep. REM sleep, which was normal in both groups at baseline, decreased significantly in the placebo group between nights 22 and 28 (during the withdrawal placebo week) compared with the zolpidem treatment group, and the number of periods of time awake increased. Minor subjective complaints were recorded under zolpidem and were comparable with those under placebo. Zolpidem seemed to improve some important sleep variables, when assessed both objectively and subjectively. The sleep cycle analysis suggested a possible shift of slow-wave sleep to an earlier period of the night, with a more physiological sleep structure. There was no evidence for withdrawal or rebound after stopping the 2 weeks of zolpidem treatment, but rather signs that the effect of zolpidem outlasted active treatment. The present pilot study justifies a prospective confirmatory comparison of zolpidem with benzodiazepines in an adequate number of patients and withdrawal after 6-8 weeks of treatment.

Adult

Zolpidem: a nonbenzodiazepine hypnotic for treatment of insomnia.

The pharmacology, pharmacokinetics, and clinical efficacy of zolpidem tartrate, a new hypnotic agent, are described. Zolpidem belongs to the imidazopyridine class. It exhibits high-affinity binding at a benzodiazepine-receptor subtype that is located in the cerebellum and cerebral cortex but not in the spinal cord or peripheral tissues. It decreases sleep latency and increases total sleep time and sleep efficiency without affecting sleep architecture. Zolpidem tartrate is absorbed rapidly. Bioavailability is 67% after oral doses of 5-20 mg. Pharmacokinetics show age-related and sex-related variations. The disposition of zolpidem is reduced in hepatically and renally impaired patients. Clinical studies have shown effectiveness of zolpidem in increasing sleep time and decreasing sleep latency. It has demonstrated efficacy equal to that of benzodiazepines without causing rebound insomnia or withdrawal effects. Comparative trials have found zolpidem as effective as flunitrazepam, flurazepam, and triazolam. The optimum dose of zolpidem tartrate is 10 mg at bedtime; 5 mg for elderly patients. Adverse reactions to zolpidem are dose-related and have primarily CNS and gastro-intestinal manifestations. Zolpidem exhibits similar efficacy to the benzodiazepines in the treatment of insomnia. Zolpidem's advantages over benzodiazepines are that it does not lead to tolerance, withdrawal phenomena, or REM rebound; however, for short-term, as-needed use, these advantages are not relevant.

Clinical Trials as Topic

The discriminative stimulus properties of zolpidem, a novel imidazopyridine hypnotic.

Zolpidem is a non-benzodiazepine hypnotic drug which displaces benzodiazepines from their binding sites in different brain structures. Previous work has demonstrated several differences between zolpidem and benzodiazepines, including differences between the stimulus properties of zolpidem and chlordiazepoxide. In the present study the discriminative stimulus properties of zolpidem were analysed by training rats to discriminate between this drug and saline. It was found that stimulus control developed readily with 2 mg/kg but not with 1 mg/kg zolpidem. The effect was dose-related, had a short duration of action and was antagonised by Ro 15-1788. Furthermore, stimulus control produced by zolpidem was associated with marked reductions in rates of responding. Injections of chlordiazepoxide, triazolam, lorazepam, zopiclone, CL 218,872 and pentobarbital produced dose-related responding on the zolpidem-associated lever but haloperidol did not. However, in general, the doses of those drugs which produced drug-lever responding also reduced response rates. It is possible that the above mentioned differences between the discriminative stimulus produced by zolpidem in rats and those produced by other sedatives may be due to a selective action of zolpidem on a sub-type of benzodiazepine binding site.

Animals

Zolpidem excretion in breast milk.

Five, lactating, healthy white women were treated with a single 20 mg tablet of zolpidem 3-4 days after the delivery of a full term baby. The drug was administered at 20.00 h, 30 min after dinner, and milk samples were collected before and 3, 13 and 16 h. Venous blood 5 ml was taken before and 1.5, 3, 13, 16 h after zolpidem administration. The apparent elimination half life, estimated from plasma zolpidem concentrations was 2.6 h. The amount of zolpidem excreted in the milk at 3 h ranged between 0.76 and 3.88 micrograms, which represented 0.004 to 0.019% of the administered dose; no detectable (below 0.5 ng/ml) zolpidem was found in the milk at subsequent sampling times. The ratio of the zolpidem concentrations in breast milk and plasma at 3 h was 0.13. The apparent breast milk clearance of zolpidem, calculated from the ratio of the total amount of zolpidem excreted in milk to its AUC in plasma was 1.48 ml/h. The results show that the excretion of zolpidem in human milk is very low (below 0.02%) and that most of it takes place during the first 3 h following drug intake.

Adult

Regional differences in the effects of chronic ethanol administration on [3H]zolpidem binding in rat brain.

A strong association has been observed between [3H]zolpidem binding and the presence of gamma-aminobutyric acid (GABAA) receptor mRNA for alpha 1-, beta 2-, and gamma 2-subunits in specific brain regions. This correlates with observed sensitivity of individual neurons to zolpidem and ethanol in these same regions. Previous studies using homogenate binding approaches showed small alterations in [3H]zolpidem binding levels after chronic ethanol exposure. This study was undertaken to ascertain if there is regional specificity of the effects of chronic ethanol administration on [3H]zolpidem binding levels. Chronic ethanol administration induced small, but significant alterations in [3H]zolpidem (5 nM) binding in the inferior colliculus, substantia nigra, and the medial septum. [3H]Zolpidem binding was increased in the inferior colliculus and substantia nigra, and decreased in the medial septum. No significant differences in [3H]zolpidem binding were noted in any other brain area analyzed, including the cortex and cerebellum. These findings show that chronic ethanol administration has small effects on [3H]zolpidem binding, although they occur in a site-specific and bidirectional manner. Moreover, there is no correlation between changes in [3H]zolpidem binding and alterations in GABAA receptor subunit expression.

Alcoholism