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PubMed2000

Discriminative-stimulus effects of zolpidem, triazolam, pentobarbital, and caffeine in zolpidem-trained humans.

Six non-drug-abusing humans were trained to discriminate 15 mg zolpidem in the present experiment. After participants acquired discrimination, a range of doses of zolpidem (2.5-15.0 mg), triazolam (0.0625-0.3750 mg), pentobarbital (25-150 mg), caffeine (100-600 mg), and placebo were tested to determine whether they shared discriminative-stimulus effects with 15 mg zolpidem. The participant-rated and performance-impairing effects of zolpidem, triazolam, pentobarbital, and caffeine were assessed concurrently. Triazolam and pentobarbital dose dependently increased zolpidem-appropriate responding. Caffeine occasioned low levels of zolpidem-appropriate responding. Zolpidem, triazolam, and pentobarbital, but not caffeine, generally produced a similar constellation of participant-rated drug effects (e.g., increased scores for the Pentobarbital, Chlorpromazine, and Alcohol Group subscale on the Addiction Research Center Inventory) and dose dependently impaired performance. These results suggest that humans can reliably discriminate zolpidem. Despite its unique benzodiazepine-receptor binding profile, the discriminative-stimulus, participant-rated, and performance-impairing effects of zolpidem are similar to those of the barbiturates and benzodiazepines.

Adult↗

PubMed1988

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↗

PubMed2005

Comparative cue generalization profiles of L-838, 417, SL651498, zolpidem, CL218,872, ocinaplon, bretazenil, zopiclone, and various benzodiazepines in chlordiazepoxide and zolpidem drug discrimination.

The zolpidem discriminative cue is mediated by GABA(A)-alpha1 receptors, whereas the chlordiazepoxide cue may be mediated via non-alpha1 GABA(A) receptors because compounds with selective affinity for GABA(A)-alpha1 receptors fully generalize to the former cue. We predicted that L-838,417 [7-tert-butyl-3-(2,5-difluorophenyl)-6-(2-methyl-2H-1,2,4-triazol-3-ylmethoxy)-1,2,4-triazolo[4,3-b]pyridazine], a partial agonist at non-alpha1 GABA(A) receptors and an antagonist at GABA(A)-alpha1 receptors, would generalize to the chlordiazepoxide but not the zolpidem-discriminative cue. SL651498 [6-fluoro-9-methyl-2-phenyl-4-(pyrrolidin-1-yl-carbonyl)-2,9-dihydro-1H-pyridol[3,4-b]indol-1-one] is a full agonist at GABA(A)-alpha2 receptors, with lower efficacy at GABA(A)-alpha3 receptors and least efficacy at GABA(A)-alpha1 and GABA(A)-alpha5 receptors. Because SL651498 has efficacy at GABA(A)-alpha1 receptors, we anticipated that it would generalize to both discriminative cues. Rats were trained to discriminate either zolpidem (3 mg/kg) or chlordiazepoxide (5 mg/kg) from vehicle using a two-lever operant procedure. The generalization profiles of L-838,417 and SL651498 were compared with nonselective full agonists, GABA(A)-alpha1-selective ligands zolpidem and CL218,872 [3-methyl-6-[3-(trifluoromethyl)phenyl]-1,2,4-triazolo[4,3-b]pyridazine], the nonselective partial agonist bretazenil, and the novel anxioselective drug ocinaplon. A nonselective partial agonist was included because L-838,417 and SL651498 are partial agonists at some GABA(A) receptors, and this property may influence their generalization profiles. All nonselective full agonists and ocinaplon fully generalized to both cues. CL218,872 and zolpidem generalized to zolpidem only, whereas L-838,417 fully generalized to chlordiazepoxide only. SL651498 fully generalized to chlordiazepoxide and occasioned significant zolpidem-appropriate responding. Bretazenil was similar to SL651498. In conclusion, at this training dose, the chlordiazepoxide-discriminative stimulus is mediated primarily via non-alpha1 GABA(A) receptors and the generalization profiles of the ligands tested seem to correspond with their in vitro profiles at GABA(A) receptor subtypes.

Animals↗

PubMed1988

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↗

PubMed2006

Dynamics and kinetics of a modified-release formulation of zolpidem: comparison with immediate-release standard zolpidem and placebo.

Modified-release (MR) zolpidem was developed to maintain effective plasma concentrations during the 3- to 6-hour post-dosage interval, corresponding to the middle portion of the typical sleep interval. Modified-release zolpidem (12.5 mg), standard immediate-release (IR) zolpidem (10 mg), and placebo were compared in a double-blind, single-dose, 3-way crossover daytime study of healthy volunteers (n = 70 completers). Effect areas for electroencephalographic beta amplitude during 0 to 8 hours and 3 to 6 hours after dosage were greater for MR compared to IR (P < .001). The digit-symbol substitution test and sedation rating scales behaved similarly. MR and IR did not differ in effects at 8 hours post-dosage nor in halflife or clearance. Time of peak plasma concentration (tmax) was significantly longer for MR (2.4 vs 2.0 hours, P < .004), and dose-normalized peak plasma concentration (Cmax) was lower (12.2 vs 14.0 ng/mL/mg, P < .001). MR zolpidem also had greater area under the plasma concentration curve (AUC) during the 3- to 6-hour interval (P < .001). Thus, MR zolpidem produces sustained plasma levels compared to IR, with resulting enhancement of pharmacodynamic effects in the 3- to 6-hour post-dosage interval.

Adult↗

PubMed1996

The effect of co-administration of zolpidem with fluoxetine: pharmacokinetics and pharmacodynamics.

Since early treatment of depression with Selective Serotonin Reuptake Inhibitor (SSRI) can be associated with insomnia, daytime antidepressive therapy with SSRI is often combined with nighttime administration of a hypnotic. This study attempted to evaluate the pharmacokinetic and pharmacodynamic interactions between zolpidem 10 mg, a short-acting hypnotic, and fluoxetine 20 mg, an SSRI. Twenty-seven healthy male volunteers (mean age 23.5 years, range 20 - 29) received zolpidem and fluoxetine in the following open design: zolpidem on night 1, a morning dose of fluoxetine daily from day 2 through day 18 and zolpidem on night 18. Using HPLC, plasma levels of zolpidem, fluoxetine, and norfluoxetine were determined throughout night 1 for zolpidem, night 18 for zolpidem, fluoxetine, and norfluoxetine on days 16 and 17 for fluoxetine and norfluoxetine. Morning psychomotor tests were performed on days 1, 2, 18, and 19. Statistical analysis of data consisted of repeated measures of ANOVA. There was no significant difference in AUC, C(max), and T1/2 of zolpidem plasma concentrations between night 1 (zolpidem) and night 18 (zolpidem and fluoxetine). There was a significantly higher zolpidem plasma level at 0.5 hours after dosing together with a significantly shorter T(max) on night 18 compared to night 1. There was no significant difference in C(min) of plasma fluoxetine and norfluoxetine levels between day 16 and 17 of fluoxetine dosing, and there was no difference in T(max) between day 17 (fluoxetine) and day 18 (fluoxetine and zolpidem). There was a 3 - 4% increase in AUC and C(max) of fluoxetine and norfluoxetine plasma concentrations in the presence of zolpidem. There was no difference in the next morning performance tests after nighttime treatment of zolpidem alone after 17 consecutive days of fluoxetine treatment, or after zolpidem in the presence of steady-state plasma concentrations of fluoxetine. Both zolpidem and fluoxetine were well tolerated alone or in combination. It is concluded that the onset of action of zolpidem may possibly be shortened in the presence of fluoxetine, but no other significant pharmacokinetic or pharmacodynamic interactions occurred between zolpidem and fluoxetine.

Adult↗

PubMed1998

Kinetic and dynamic interaction study of zolpidem with ketoconazole, itraconazole, and fluconazole.

BACKGROUND: Azole antifungal agents may impair hepatic clearance of drugs metabolized by cytochrome P450-3A isoforms. The imidazopyridine hypnotic agent zolpidem is metabolized in humans in part by P450-3A, as well as by a number of other cytochromes. Potential interactions of zolpidem with 3 commonly prescribed azole derivatives were evaluated in a controlled clinical study. METHODS: In a randomized, double-blind, 5-way, crossover, clinical pharmacokinetic-pharmacodynamic study, 12 volunteers received (A) zolpidem placebo plus azole placebo, (B) 5 mg zolpidem plus azole placebo (C) zolpidem plus ketoconazole, (D) zolpidem plus itraconazole, and (E) zolpidem plus fluconazole. RESULTS: Mean apparent oral clearance of zolpidem when given with placebo was 422 mL/min, and elimination half-life was 1.9 hours. Clearance was significantly reduced to 250 mL/min when zolpidem was given with ketoconazole, and half-life was prolonged to 2.4 hours. Coadministration of zolpidem with itraconazole or fluconazole also reduced clearance (320 and 338 mL/min), but differences compared to the zolpidem plus placebo treatment did not reach significance. Zolpidem-induced benzodiazepine agonist effects (increased electrocardiographic beta activity, digit-symbol substitution test impairment, and delayed recall) during the first 4 hours after dosage were enhanced by ketoconazole but not by itraconazole or fluconazole. CONCLUSION: Coadministration of zolpidem with ketoconazole impairs zolpidem clearance and enhances its benzodiazepine-like agonist pharmacodynamic effects. Itraconazole and fluconazole had a small influence on zolpidem kinetics and dynamics. The findings are consistent with in vitro studies of differentially impaired zolpidem metabolism by azole derivatives.

Administration, Oral↗

PubMed2006

Pharmacokinetic profile of a new modified release formulation of zolpidem designed to improve sleep maintenance.

The aim of this study was to compare the relative bioavailability and the pharmacokinetic profile of a single oral dose of a zolpidem modified-release (MR) 12.5-mg formulation with those of the standard 10-mg zolpidem immediate-release (IR) formulation. Absolute bioavailabilities of oral formulations were evaluated using intravenously (i.v.) administered zolpidem as a reference. Twenty-four healthy, Caucasian, male volunteers (18-45 years old) received single doses of three oral formulations (zolpidem-MR 12.5 mg, zolpidem-IR 10 mg and an experimental form) and zolpidem i.v. infusion (8 mg) in a randomized, open-label, crossover trial. Blood samples (18 time-points) were collected up to 16 h post-dose after oral administration and up to 12 h post-dose after i.v. administration. Pharmacokinetic parameters were determined by non-compartmental analysis, allowing comparisons between treatments based on estimated ratios and differences, with 90% confidence intervals. The initial absorption phase of the zolpidem-MR formulation was as fast as that of zolpidem-IR with no significant difference in t(max). With zolpidem-MR 12.5 mg, C(max) was moderately lower than with zolpidem-IR (ratio of 0.82), and plasma zolpidem concentrations were maintained above those observed with zolpidem-IR for a longer period of time, particularly from 3 to 6 h post-dose. This was confirmed by an increase in half-value duration (HVD) from 2.3 h with zolpidem-IR to 4.6 h with zolpidem-MR 12.5 mg. The mean terminal half-life was similar between formulations. Zolpidem-MR 12.5 mg provides the appropriate pharmacokinetic characteristics to extend plasma zolpidem concentrations into the middle of the night (3-6 h post-dose), while retaining the same t(max) and terminal half-life.

Administration, Oral↗

PubMed1996

[Acute overdose of Zolpidem (Stilnox)].

Zolpidem (Stilnox), an imidazopyridine derivative, is a strong sedative with minor myorelaxant and anticonvulsant properties which exhibits high-affinity binding at a benzodiazepine-receptor subtype. Although the structure of zolpidem differs from the benzodiazepines, the acute toxicity of zolpidem has generally been compared to triazolam (Halcion) and midazolam (Dormicum). 5 years after introduction of zolpidem to the Swiss market we have therefore retrospectively analyzed 91 well documented cases of acute zolpidem intoxication reported to the Swiss Toxicological Information Center. Furthermore, 54 single-drug poisonings with zolpidem were compared with 53 triazolam and 55 midazolam intoxications observed over the same time period. 0.01-0.02 g of zolpidem is the recommended therapeutic dose. But only mild symptoms were observed in acute single-drug poisonings with zolpidem up to 0.6 g. Patients mainly suffered from somnolence. Only one anorectic patient became comatose after ingestion of 0.6 g zolpidem. The acute toxicity of zolpidem was markedly less pronounced than that of the short-acting benzodiazepines triazolam and midazolam. With forty-fold the therapeutic dose no severe symptoms occurred in patients with zolpidem single-drug poisonings, while coma was encountered in 4 cases with triazolam (11% of patients) and 4 cases with midazolam (10%). While only the patient mentioned above was reported to be comatose after overdosing with zolpidem, 6 (11%) and 8 (15%) comatose patients were observed in triazolam and midazolam single-drug poisonings, respectively. On the other hand, in combined intoxications with other CNS active drugs or ethanol a zolpidem dose as low as 0.1-0.15 s induced coma in some patients, even if the amount of the additionally ingested drugs in itself would not have caused a comatose state. Flumazenil (Anexate) was an effective antidote in mono- and combined intoxications involving zolpidem. In conclusion, our results indicate that zolpidem single-drug poisonings are generally benign and require no specific therapeutic measures. In combined intoxications, however, patients may develop coma at relatively low zolpidem doses and should therefore be monitored for approximately 24 hours. If necessary, disturbances of consciousness can be successfully treated with flumazenil.

Adolescent↗

PubMed1998

Zolpidem 10 mg given at daytime is not antagonized by 300 mg caffeine in man.

OBJECTIVE: Caffeine counteracts various effects of traditional benzodiazepines (BZDs). As zolpidem, a short-acting hypnotic, is an atypical GABAA-BZD agonist, we investigated when caffeine would counteract the effects of zolpidem as well. METHODS: In daytime study I, zolpidem 10 mg (capsule) and caffeine 150 or 300 mg (in decaffeinated coffee) were given, alone and in combinations, to parallel groups (n = 15-17) of healthy students in double-blind and placebo-controlled manner. Objective and subjective tests were done before and 45 min and 90 min after intake. Ranked delta values (changes from baseline) were analysed by one-way contrast ANOVA and Scheffe's tests. In daytime study II, four healthy subjects took zolpidem 10 mg alone, and together with blinded caffeine 250 mg or (at -45 min) erythromycin 750 mg. Objective and subjective effects were measured and plasma zolpidem concentrations assayed at baseline and 45 min and 90 min after zolpidem intake. RESULTS: In study I, practice effects after placebo (ad + 30%) were seen for letter cancellation and digit symbol substitution but not for flicker fusion tests. Zolpidem alone significantly impaired (P < 0.05 vs delta placebo) letter cancellation and digit symbol substitution at 45 min and 90 min, lowered the flicker fusion threshold at 45 min, and caused subjective drowsiness, mental slowness, clumsiness and feeling of poor performance. Caffeine alone showed a non-significant trend to improve objective performance. The combined effects of zolpidem and either dose of caffeine matched those measured after zolpidem alone. Zolpidem + caffeine 300 mg was not stronger than zolpidem + caffeine 150 mg in impairing immediate memory and causing subjective sedation. In study II, zolpidem caused objective and subjective sedation; neither caffeine nor erythromycin modulated the effects of zolpidem or plasma zolpidem concentrations. CONCLUSION: The sedative effects of 10 mg of zolpidem are not antagonized by 150-300 mg of caffeine in pharmacodynamic or pharmacokinetic terms.

Adult↗

PubMed1995

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↗

PubMed1995

Clinical pharmacokinetics and pharmacodynamics of zolpidem. Therapeutic implications.

Zolpidem is an imidazopyridine which differs in structure from the benzodiazepines and zopiclone. It is a strong sedative with only minor anxiolytic, myorelaxant and anticonvulsant properties, and has been shown to be effective in inducing and maintaining sleep in adults. The available evidence suggests that zolpidem produces no rebound or withdrawal effects, and patients have experienced good daytime alertness. Zolpidem 10mg in non-elderly and a reduced dose of 5mg in elderly individuals are clinically effective. In humans, the major metabolic routes include oxidation and hydroxylation; none of the metabolites appears to be pharmacologically active. The pharmacological activity of zolpidem results from selective binding to the central benzodiazepine receptors of the omega 1 subtype. Zolpidem is approximately 92% bound to plasma proteins; absolute bio-availability of zolpidem is about 70%. After single 20mg oral doses, typical values of pharmacokinetic variables for zolpidem in humans are: a peak plasma concentration of 192 to 324 micrograms/L occurring 0.75 to 2.6 hours postdose; a terminal elimination half-line of 1.5 to 3.2 hours; and total clearance of 0.24 to 0.27 ml/min/kg. Zolpidem pharmacokinetics are unchanged during multiple-dose treatment. Zolpidem pharmacokinetics are not significantly influenced by gender. Clearance of zolpidem in children is 3 times higher than in young adults, and is lower in very elderly people. There are no significant differences in the pharmacokinetic parameters between various racial groups. Dosage reduction appears to be prudent in patients with renal disease, and caution should be exercised when prescribing zolpidem to elderly patients with hepatic impairment. Coadministration of haloperidol, cimetidine, ranitidine, chlorpromazine, warfarin, digoxin or flumazenil do not alter the pharmacokinetics of zolpidem; flumazenil predictably antagonises the hypnotic effects of zolpidem. Alertness tends to be reduced when cimetidine is combined with zolpidem. Volunteers treated with imipramine plus zolpidem developed anterograde amnesia.

Adult↗

PubMed1995

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↗

PubMedDate not supplied

Action of zolpidem on responses to GABA in relation to mRNAs for GABA(A) receptor alpha subunits within single cells: evidence for multiple functional GABA(A) isoreceptors on individual neurons.

The relationship between zolpidem sensitivity and GABA(A) receptor alpha subunits was studied in individual dissociated neurons from rat brain. Using whole-cell recording, similar EC50 values were demonstrated for the effect of gamma-aminobutyric acid (GABA) on gated-chloride currents from substantia nigra reticulata (SNR) and lateral septal neurons. Subsequently, many neurons from both the SNR or lateral septum were found to exhibit enhanced GABA-gated chloride currents across concentrations of zolpidem ranging from 10 to 300 nM. Some neurons exhibited a greater than 20% increase in responsiveness to GABA at 30 nM of zolpidem without further increase at higher concentrations of zolpidem. Conversely, zolpidem enhancement of GABA from another group of neurons was not observed at 30 nM zolpidem, but between 100 and 300 nM the response to GABA increased greater than 20%. Finally, a third group of neurons reached both of these criteria for zolpidem enhancement of GABA. This latter spectrum of responses to GABA after varying concentrations of zolpidem was consistent with the presence of either two GABA(A) receptors or a single receptor with differing affinities for zolpidem on an individual neuron. Following determination of the sensitivity of neurons from SNR or lateral septum to zolpidem, cytoplasm was extracted from some individual cells to allow identification of cellular mRNAs for the alpha1, alpha2 and alpha3 GABA(A) receptor subunits with RT-PCR. Those neurons that responded to the 30 nM zolpidem concentration invariably expressed the alpha1-GABA(A) receptor subunit. This result is consistent with the GABA(A) alpha1-receptor subunit being an integral part of a functional high-affinity zolpidem type 1-BZD receptor complex on neurons in brain. Those neurons which showed enhancement of GABA from 100 to 300 nM zolpidem contained mRNAs for the alpha2 and/or the alpha3 receptor subunits, a finding consistent with these alpha subunits forming type 2-BZD receptors. Some individual dissociated SNR neurons were sensitive to both low and high concentrations of zolpidem and contained mRNAs for all three alpha-receptor subunits. These latter individual neurons are proposed to have at least two functional GABA(A) receptor subtypes. Thus, the present investigation emphasizes the importance of characterizing the relationship between endogenous GABA(A) receptor function and the presence of specific structural components forming GABA(A) receptor subtypes on neurons.

Animals↗

PubMed2003

Pharmacokinetic properties of zolpidem in elderly and young adults: possible modulation by testosterone in men.

AIMS: The influence of ageing on the pharmacokinetics of zolpidem, an extensively prescribed hypnotic medication, was evaluated in healthy human volunteers. METHODS: A series of 16 elderly (age: 61-85 years) and 24 young (age: 22-42 years) volunteers received single 5 mg oral doses of zolpidem tartrate. Serum zolpidem concentrations were determined by HPLC with fluorescence detection in samples drawn during 8 h after dosage. The effect of testosterone on zolpidem biotransformation was evaluated in vitro using human liver microsomes. Possible induction of CYP3A protein expression and function was studied in cultured human hepatocytes. RESULTS: Among men, apparent oral clearance of zolpidem was decreased in elderly compared to young subjects (3.8 vs 11.0 ml min-1 kg-1, P < 0.01), Cmax was increased (93 vs 40 ng ml-1, P < 0.01), and half-life increased (2.7 vs 1.5 h, P < 0.03). Among women, zolpidem oral clearance was decreased in the elderly (3.0 vs 5.8 ml min-1 kg-1, P < 0.02), Cmax increased (108 vs 60 ng ml-1, P < 0.001), with no difference in t1/2 (2.3 vs 2.4 h). Among male subjects, free serum testosterone concentrations were lower in the elderly (10.5 vs 19.0 pg ml-1, P < 0.01), and were significantly correlated with zolpidem clearance (r2 = 0.46, P < 0.001). Multiple regression analysis indicated a greater relative contribution of serum testosterone than age to the oral clearance of zolpidem among men. In human liver microsomes, co-incubation of zolpidem (10 micro m) with varying concentrations of testosterone produced activation of biotransformation of zolpidem to its principal hydroxylated metabolite. Maximum activation was achieved at equimolar concentrations of testosterone (10 micro m). However, testosterone did not induce immunoactive CYP3A4 expression or catalytic function in cultured human hepatocytes. CONCLUSIONS: The increased Cmax and lower oral clearance of zolpidem in the elderly are consistent with recommendations of lower clinical doses of zolpidem in the elderly. Our clinical and in vitro data both suggest that reduced free serum testosterone may have a modulatory role in age-dependent changes in zolpidem pharmacokinetics in men.

Administration, Oral↗

PubMed2006

Zolpidem extended-release.

Zolpidem extended-release, or controlled-release (CR), is a new formulation of zolpidem, a nonbenzodiazepine hypnotic. It is indicated in the US for the treatment of insomnia, characterised by difficulties with sleep onset and/or sleep maintenance. Zolpidem CR is a dual-layered tablet; one layer releases zolpidem immediately and a second layer provides a slower release of additional zolpidem for maintenance of plasma zolpidem concentrations. Efficacy of zolpidem CR was assessed in two 3-week, randomised, double-blind, placebo-controlled, phase III polysomnography trials in younger adult (aged 18-64 years) or elderly (aged > or =65 years) patients with primary insomnia. Patients received nightly zolpidem CR (12.5mg in younger adult and 6.25mg in elderly patients). Efficacy was assessed objectively on nights 1, 2, 15 and 16. Patients who received zolpidem CR had significantly improved objective latency to persistent sleep, wake time after sleep onset and sleep efficiency on assessment nights compared with placebo recipients. In subjective assessments of sleep quality on day 2 and nights 15 and 22, significantly more zolpidem CR than placebo recipients gave favourable responses on a Patient Global Impression scale in the study in younger adult patients. In the other study, significantly more elderly patients in the zolpidem CR group rated their sleep as improved compared with the placebo group. Zolpidem CR was generally well tolerated and appears to have a tolerability profile similar to that of the original formulation of zolpidem.

Adolescent↗

PubMed1994

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↗

PubMed2004

Zolpidem prescribing and adverse drug reactions in hospitalized general medicine patients at a Veterans Affairs hospital.

BACKGROUND: Zolpidem is prescribed for sleep disruption in hospitalized patients, but data on the incidence of adverse drug reactions (ADRs) are based largely on outpatient studies. Thus, the incidence of ADRs in hospitalized patients may be much higher. OBJECTIVE: The goal of this study was to describe prescribing patterns of zolpidem for hospitalized medical patients aged 50 years, the incidence of ADRs possibly and probably associated with its use, and the factors associated with central nervous system (CNS) ADRs. METHODS: This case series was conducted in 4 general medicine wards at a Veterans Affairs hospital and was a consecutive sample of patients aged 50 years who were hospitalized between 1993 and 1997 and received zolpidem as a hypnotic during hospitalization, but had not received it in the previous 3 months. Chart review was conducted by 2 evaluators. Data extracted from the medical records included admission demographic characteristics, medications, comorbidities, and levels of function in performing basic and instrumental activities of daily living. The main outcome measure was ADRs possibly or probably related to zolpidem use. The association between zolpidem and the occurrence of CNS ADRs (eg, confusion, dizziness, daytime somnolence) was analyzed separately. RESULTS: The review included 119 medical patients aged > or =50 years who had newly received zolpidem for sleep disruption during hospitalization. The median age of the population was 70 years; 86 (72.3%) patients were aged 65 years. The initial zolpidem dose was 5 mg in 42 patients (35.3%) and 10 mg in 77 patients (64.7%). Twenty-three patients had a respective 16 and 10 ADRs possibly and probably related to zolpidem use (19.3% incidence). Of a total of 26 ADRs, 21 (80.8%) were CNS ADRs, occurring with both zolpidem 5 mg (10.8% of users) and 10 mg (18.3% of users). On univariate analyses, the only factor significantly associated with a CNS ADR was functional impairment at baseline (P = 0.003). Zolpidem was discontinued in 38.8% of patients experiencing a CNS ADR CONCLUSIONS: In this case series in medical inpatients, there was a high frequency of ADRs, particularly CNS ADRs, associated with zolpidem use. Zolpidem should be used cautiously in the hospital setting.

Aged↗