Zolpidem: a review of its use in the management of insomnia

N-Bridged 5,6-bicyclic pyridines: Recent applications in central nervous system disorders

The search for novel heterobicyclic compounds within the drug-like chemical space continues to be an area of interest in medicinal chemistry. Unsaturated N-bridgehead heterocycles are well represented in marketed drugs for a variety of therapeutic areas, and continue to play an important role in central nervous system (CNS) drug discovery programs. Examples of medicinal chemistry strategies that make use of N-bridged 5,6-bicyclic pyridines are discussed here in this Minireview, which covers the literature from 2010 up to 2014. B1-class imidazopyridines and B3-class pyrazolopyridines have proven to be at the forefront of molecular prototypes that are capable of interacting with disease relevant targets in neurodegeneration and neuropsychiatry.

Three-component reaction of a 2-aminoazine, a 2-oxoaldehyde, and a cyclic 1,3-dicarbonyl compound for the synthesis of imidazo[1,2-a]azine derivatives

A three-component reaction of a 2-aminoazine, a 2-oxoaldehyde, and a cyclic 1,3-dicarbonyl compound providing access toward a novel class of imidazo[1,2-a]azine derivatives was developed and studied. The scope of the process was thoroughly explored under three different reaction conditions resulting in the generation of a small library of title compounds and highlighting the possibility of case-specific approach.

Regioselective synthesis of fused imidazo[1,2-a]pyrimidines via intramolecular C-N bond formation/6-endo-dig cycloisomerization

An efficient regioselective cascade synthesis of N-fused imidazo heterocycles has been developed. This cascade transformation proceeds via a transition-metal (copper/silver) catalyzed coupling reaction between 2-aminobenzimidazole, aldehydes, and alkynes leading to the formation of propargylamine intermediate, which regioselectively undergoes 6-endo-dig cyclization through intramolecular N-H bond activation interceded C-N bond formation leading to highly functionalized imidazo[1,2-a]pyrimidines in good to excellent yields.

The behavioral pharmacology of zolpidem: evidence for the functional significance of α1-containing GABA(A) receptors

RATIONALE

Zolpidem is a positive allosteric modulator of γ-aminobutyric acid (GABA) with preferential binding affinity and efficacy for α1-subunit containing GABA(A) receptors (α1-GABA(A)Rs). Over the last three decades, a variety of animal models and experimental procedures have been used in an attempt to relate the behavioral profile of zolpidem and classic benzodiazepines (BZs) to their interaction with α1-GABA(A)Rs.

OBJECTIVES

This paper reviews the results of rodent and non-human primate studies that have evaluated the effects of zolpidem on motor behaviors, anxiety, memory, food and fluid intake, and electroencephalogram (EEG) sleep patterns. Also included are studies that examined zolpidem's discriminative, reinforcing, and anticonvulsant effects as well as behavioral signs of tolerance and withdrawal.

RESULTS

The literature reviewed indicates that α1-GABA(A)Rs play a principle role in mediating the hypothermic, ataxic-like, locomotor- and memory-impairing effects of zolpidem and BZs. Evidence also suggests that α1-GABA(A)Rs play partial roles in the hypnotic, EEG sleep, anticonvulsant effects, and anxiolytic-like of zolpidem and diazepam. These studies also indicate that α1-GABA(A)Rs play a more prominent role in mediating the discriminative stimulus, reinforcing, hyperphagic, and withdrawal effects of zolpidem and BZs in primates than in rodents.

CONCLUSIONS

The psychopharmacological data from both rodents and non-human primates suggest that zolpidem has a unique pharmacological profile when compared with classic BZs. The literature reviewed here provides an important framework for studying the role of different GABA(A)R subtypes in the behavioral effects of BZ-type drugs and helps guide the development of new pharmaceutical agents for disorders currently treated with BZ-type drugs.

Ruthenium-catalyzed direct C-3 oxidative olefination of imidazo[1,2-a]pyridines

Ruthenium-catalyzed regioselective C-3 oxidative olefination of imidazo[1,2-a]pyridines.

Synthesis of Heterocyclic-fused Imidazoles by Pyrolysis of N-Heterocyclic Isoxazol-5(2H)-ones

The synthesis of heterocyclic-fused imidazoles was achieved by flash vacuum pyrolysis (FVP) of N-heterocyclic isoxazol-5(2H)-ones via an iminocarbene intermediate. Unlike iminocarbenes generated from triazoles, no structural rearrangements were observed during the current synthesis method. We also demonstrated that less volatile isoxazol-5(2H)-one derivatives yield the corresponding imidazoles by condensed phase pyrolysis.

Synthesis of biologically active pyridoimidazole/imidazobenzothiazole annulated polyheterocycles using cyanuric chloride in water

An efficient and mild protocol for rapid access to N-fused polyheterocycles via Pictet–Spengler type 6-endo cyclization by cyanuric chloride in aqueous medium has been developed.

Use of non-benzodiazepine sedative hypnotics and risk of falls in older men

BACKGROUND

To ascertain whether use of non-benzodiazepine sedative-hypnotics is associated with risk of falls and compare this to risk of falls associated with use of benzodiazepines.

METHODS

Among 4450 community-dwelling men, aged 71 years and older, enrolled in the population-based prospective cohort study, Osteoporotic Fractures in Men (MrOS), use of nonbenzodiazepine sedative-hypnotics and benzodiazepines was assessed by interview and verified from medication containers at the third annual visit of the MrOS study. Falls in the subsequent one-year period were ascertained by tri-annual questionnaires and a computerized dictionary used to categorize type of medication.

RESULTS

In age-adjusted models, non-benzodiazepine sedative hypnotic use was associated with an increased risk of any falls (one or more falls) (RR 1.44, 95% CI 1.15, 1.81) and recurrent falls (2 or more falls) (RR 1.51, 95% CI 1.07, 2.14). Use of benzodiazepines was associated with a similar increase in age-adjusted risk of falling. Depressive symptoms, inability to stand from a chair, and instrumental activities of daily living (IADL) impairment modestly attenuated these associations. The association between non-benzodiazepine sedative-hypnotic use and falls was most pronounced among men without a history of falls in the previous year: in a multivariable model controlling for multiple potential confounders, the RR of any falls was 1.74 (95% CI 1.13, 2.68) in this subgroup.

CONCLUSIONS

Use of non-benzodiazepine sedative-hypnotics is associated with an increased risk of falls. Non-pharmacologic approaches to sleep disturbances may represent the safest approach to sleep difficulties in older adults.

Zolpidem-induced suicide attempt: a case report

Zolpidem is a popular drug indicated for the short-term treatment of insomnia. Side effects are not uncommon with zolpidem. Herein we describe an Iranian 27-year-old man with no known mood disorder or neuropsychological disease who attempted suicide upon taking zolpidem. There are two interesting facts about this case: Firstly, the patient had not history of suicide attempt or thinking. Secondly, this case had experienced suicide ideation after taking 20 mg of zolpidem, suggesting a possible correlation between zolpidem psychological effects and dangerous psychological behaviors.

The clinical and forensic toxicology of Z-drugs

The Z-drugs zolpidem, zopiclone, and zaleplon were hailed as the innovative hypnotics of the new millennium, an improvement to traditional benzodiazepines in the management of insomnia. Increasing reports of adverse events including bizarre behavior and falls in the elderly have prompted calls for caution and regulation. Z-drugs have significant hypnotic effects by reducing sleep latency and improving sleep quality, though duration of sleep may not be significantly increased. Z-drugs exert their effects through increased γ-aminobutyric acid (GABA) transmission at the same GABA-type A receptor as benzodiazepines. Their pharmacokinetics approach those of the ideal hypnotic with rapid onset within 30 min and short half-life (1-7 h). Zopiclone with the longest duration of action has the greatest residual effect, similar to short-acting benzodiazepines. Neuropsychiatric adverse events have been reported with zolpidem including hallucinations, amnesia, and parasomnia. Poisoning with Z-drugs involves predominantly sedation and coma with supportive management being adequate in the majority. Flumazenil has been reported to reverse sedation from all three Z-drugs. Deaths from Z-drugs are rare and more likely to occur with polydrug overdose. Z-drugs can be detected in blood, urine, oral fluid, and postmortem specimens, predominantly with liquid chromatography-mass spectrometry techniques. Zolpidem and zaleplon exhibit significant postmortem redistribution. Zaleplon with its ultra-short half-life has been detected in few clinical or forensic cases possibly due to assay unavailability, low frequency of use, and short window of detection. Though Z-drugs have improved pharmacokinetic profiles, their adverse effects, neuropsychiatric sequelae, and incidence of poisoning and death may prove to be similar to older hypnotics.

Multicomponent solvent-free synthesis of benzimidazolyl imidazo[1,2-a]-pyridine under microwave irradiation

A novel one-pot, three-component reaction employing variously substituted benzimidazole-linked amino pyridines, aldehydes, and isonitriles catalyzed by scandium(III) triflate under solvent-free conditions were accomplished. This new synthetic methodology facilitates the rapid generation of intricate molecular frameworks in three-dimensional fashion leading to benzimidazole-imidazo[1,2-a] pyridines. This approach is envisioned as an environmentally benign process and a simple operation to the biological interesting compounds. The present synthetic sequence permits the introduction of three points of structural diversity to expand chemical space with high purity and excellent yields.

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.

Sublingual zolpidem (Edluar™; Sublinox™)

Zolpidem is a non-benzodiazepine hypnotic used in the short-term treatment of insomnia. A sublingual orally disintegrating tablet formulation of zolpidem (Edluar™; Sublinox™) has been developed to provide a more rapid onset of action than oral immediate-release zolpidem. Sublingual zolpidem has demonstrated bioequivalence to oral zolpidem. In a randomized, double-blind, double-dummy, crossover, multi-centre study in adult patients with primary insomnia (n = 70), a single 10-mg dose of sublingual zolpidem significantly reduced latency to persistent sleep (primary endpoint) compared with a single 10-mg dose of oral immediate-release zolpidem. Sleep-onset latency and latency to stage 1 sleep were also significantly shorter with sublingual zolpidem than with oral zolpidem. Moreover, compared with the oral formulation, sublingual zolpidem was noninferior in terms of total sleep time and did not significantly differ in terms of duration of wake after sleep onset. Sublingual zolpidem was generally well tolerated in this trial, with most adverse events being of mild or moderate severity. The overall tolerability profile of sublingual zolpidem was similar to that of oral zolpidem.

CYP3A4 and CYP2C19 genetic polymorphisms and zolpidem metabolism in the Chinese Han population: a pilot study

Zolpidem (ZPD) is an imidazopyridine hypnotic and little is known about the pharmacogenetics of ZPD. Our objective was to evaluate inter-individual genetic variation in conjunction with metabolic ratios of ZPD found in a toxicological analysis. Healthy individuals (n=300) were genotyped for CYP2D6, CYP2C19, CYP2C9, CYP3A4 and CYP1A2 by allele-specific primer extension followed by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS). Twenty-four Chinese volunteers were chosen and divided into the following four groups (n=6/group): group 1: CYP3A4*18 (wild-type, W), CYP2C19*2 (W); group 2: CYP3A4*18 (mutant, M), CYP2C19*2 (W); group 3: CYP3A4*18 (W), CYP2C19*2 (M); and group 4: CYP3A4*18 (M), CYP2C19*2 (M). ZPD and its major metabolites zolpidem 6-carboxylic acid (ZCA) and zolpidem phenyl-4-carboxylic acid (ZPCA) were determined after oral administration of ZPD (10mg), using an UPLC-MS/MS method. Positive correlations between CYP3A4 and CYP2C19 alleles and ZPD metabolism were found. The results of this study show that CYP3A4*18 increases CYP3A4 activity while CYP2C19*2 reduces CYP2C19 activity; the latter mutation is associated with the poor metabolism of ZPD in the Chinese Han population. The results also suggest that genetic factors play a major role in the metabolism of individual drugs with implications for both forensic science and clinical pharmacogenetics.

Copper(II)/iron(III) co-catalyzed intermolecular diamination of alkynes: facile synthesis of imidazopyridines

A facile synthesis of imidazo[1,2-α]pyridines has been achieved by copper(II) and iron(III) co-catalyzed C-N bond formation. This reaction involves an intermolecular oxidative diamination of alkynes with high chemoselectivity and regioselectivity.