Zaleplon - a review of a novel sedative hypnotic used in the treatment of insomnia

Sleep modulating agents

Sleep and wake are two fundamental states of human existence. Conditions such as insomnia and hypersomnia can have profound negative effects on human health. Many pharmacological interventions impacting sleep and wake are available or are under development. This brief digest surveys early approaches to sleep modulation and highlights recent developments in sleep modulating agents.

Comparative analysis of zaleplon complexation with cyclodextrins and hydrophilic polymers in solution and in solid state

The aim of this work was to investigate the potential synergistic effect of water-soluble polymers (hypromellose, HPMC and polyvinylpyrrolidone, PVP) on zaleplon (ZAL) complexation with parent β-cyclodextrin (βCD) and its randomly methylated derivative (RAMEB) in solution and in solid state. The addition of HPMC to the complexation medium improved ZAL complexation and solubilization with RAMEB (K(ZAL/RAMEB)=156±5M(-1) and K(ZAL/RAMEB/HPMC)=189±8M(-1); p<0.01), while such effect was not observed for βCD (K(ZAL/βCD)=112±2M(-1) and K(ZAL/βCD/HPMC)=119±8M(-1); p>0.05). Although PVP increased the ZAL aqueous solubility from 0.22 to 0.27mg/mL, it did not show any synergistic effects on ZAL solubilization with the cyclodextrins tested. Binary and ternary systems of ZAL with βCD, RAMEB and HPMC were prepared by spray-drying. Differential scanning calorimetry, X-ray powder diffraction and scanning electron microscopy demonstrated a partial ZAL amorphization in spray-dried binary and ternary systems with βCD, while the drug was completely amorphous in all samples with RAMEB. Furthermore, inclusion complex formation in all systems prepared was confirmed by solid-state NMR spectroscopy. The in vitro dissolution rate followed the rank order ZAL/RAMEB/HPMC>ZAL/RAMEB=ZAL/βCD/HPMC>ZAL/βCD≫ZAL, clearly demonstrating the superior performance of RAMEB on ZAL complexation in the solid state and its synergistic effect with HPMC on drug solubility. Surprisingly, when loaded into tablets made with insoluble microcrystalline cellulose, RAMEB complexes had no positive effect on drug dissolution, because HPMC and RAMEB acted as a binders inside the tablets, prolonging their disintegration. Oppositely, the formulation with mannitol, a soluble excipient, containing a ternary RAMEB system, released the complete drug-dose in only 5min, clearly demonstrating its suitability for the development of immediate-release oral formulation of ZAL.

Application of spectrophotometric, densitometric, and HPLC techniques as stability indicating methods for determination of Zaleplon in pharmaceutical preparations

Spectrophotometric, spectrodensitometric and HPLC are stability indicating methods described for determination of Zaleplon in pure and dosage forms. As Zaleplon is easily degradable, the proposed techniques in this manuscript are adopted for its determination in presence of its alkaline degradation product, namely N-[4-(3-cyano-pyrazolo[1,5a]pyridin-7-yl)-phenyl]-N-ethyl-acetamide. These approaches are successfully applied to quantify Zaleplon using the information included in the absorption spectra of appropriate solutions. The second derivative (D(2)) spectrophotometric method, allows determination of Zaleplon without interference of its degradate at 235.2 nm using 0.01N HCl as a solvent with obedience to Beer's law over a concentration range of 1-10 microg ml(-1) with mean percentage recovery 100.24+/-0.86%. The first derivative of the ratio spectra ((1)DD) based on the simultaneous use of ((1)DD) and measurement at 241.8 nm using the same solvent and over the same concentration range as (D(2)) spectrophotometric method, with mean percentage recovery 99.9+/-1.07%. The spectrodensitometric analysis allows the separation and quantitation of Zaleplon from its degradate on silica gel plates using chloroform:acetone:ammonia solution (9:1:0.2 by volume) as a mobile phase. This method depends on quantitave densitometric evaluation of thin layer chromatogram of Zaleplon at 338 nm over a concentration range of 0.2-1 microg band(-1), with mean percentage recovery 99.73+/-1.35. Also a reversed-phase liquid chromatographic method using 5-C8 (22 cm x 4.6 mm i.d. 5 microm particle size) column was described and validated for quantitation of Zaleplon using acetonitrile:deionised water (35:65, v/v) as a mobile phase using Paracetamol as internal standard and a flow rate of 1.5 ml min(-1) with UV detection of the effluent at 232 nm at ambient temperature over a concentration range of 2-20 microg ml(-1) with mean percentage recovery 100.19+/-1.15%. The insignificance difference of the proposed methods results with those of the reference one proved their accuracy and precision.

High-performance liquid chromatography–atmospheric pressure chemical ionisation-mass spectrometry determination of zaleplon in human plasma

A sensitive and specific liquid chromatography-atmospheric pressure chemical ionisation-mass spectrometry (LC-APCI-MS) method has been developed and validated for the identification and quantification of zaleplon in human plasma using estazolam as an internal standard (IS). After the addition of estazolam and 2.0 M sodium hydroxide solution, plasma samples were extracted with ethyl acetate and then the organic layer was evaporated to dryness. The reconstituted solution of the residue was injected onto a prepacked Shim-pack VP-ODS C18 (250 mm x 2.0 mm i.d.) column and chromatographed with a mobile phase comprised of methanol:water (70:30) at a flow-rate of 0.2 ml/min. Detection was performed on a single quadrupole mass spectrometer by selected ion monitoring (SIM) mode via atmospheric pressure chemical ionization (APCI) source. The mean standard curve was linear (r = 0.9991) over the concentration range of 0.2-100 ng/ml and had good back-calculated accuracy and precision. The intra-day and inter-day precisions were within 10% relative standard deviation and accuracy ranged from 85% to 115%. The limit of detection was 0.1 ng/ml. The validated LC-APCI-MS method has been used successfully to study zaleplon pharmacokinetic, bioavailability and bioequivalence in 18 adult volunteers.

Use of Sleep-Promoting Medications in Nursing Home Residents

This paper reviews the use of sleep-promoting medications in nursing home residents with reference to risks versus benefits. Up to two-thirds of elderly people living in institutions experience sleep disturbance. The aetiology of sleep disturbance includes poor sleep hygiene, medical and psychiatric disorders, sleep apnoea, periodic limb movements and restless leg syndrome. One key factor in the development of sleep disturbance in the nursing home is the environment, particularly with respect to high levels of night-time noise and light, low levels of daytime light, and care routines that do not promote sleep. Clinical assessment should include a comprehensive medical, psychiatric and sleep history including a review of prescribed medications. Nonpharmacological interventions for insomnia are underutilised in many clinical settings despite evidence that they are often highly effective. International studies suggest that 50-80% of nursing home residents have at least one prescription for psychotropic medication. Utilisation rates vary dramatically from country to country and from institution to institution. The most commonly prescribed medications for sleep are benzodiazepines and nonbenzodiazepine hypnotics (Z-drugs). The vast majority of studies of these medications are short-term, i.e. < or =2 weeks, although some longer extension trials have recently been carried out. Clinicians are advised to avoid long-acting benzodiazepines and to use hypnotics for as brief a period as possible, in most cases not exceeding 2-3 weeks of treatment. Patients receiving benzodiazepines are at increased risk of daytime sedation, falls, and cognitive and psychomotor impairment. Zaleplon, zolpidem, zopiclone and eszopiclone may have some advantages over the benzodiazepines, particularly with respect to the development of tolerance and dependence. Ramelteon, a novel agent with high selectivity for melatonin receptors, has recently been approved in the US. Use of the antidepressant trazodone for sleep in nondepressed patients is somewhat controversial. Atypical antipsychotics should not be used to treat insomnia unless there is also evidence of severe behavioural symptoms or psychosis.

Postural Instability and Consequent Falls and Hip Fractures Associated with Use of Hypnotics in the Elderly

The aim of this review is to establish the relationship between treatment with hypnotics and the risk of postural instability and as a consequence, falls and hip fractures, in the elderly. A review of the literature was performed through a search of the MEDLINE, Ingenta and PASCAL databases from 1975 to 2005. We considered as hypnotics only those drugs approved for treating insomnia, i.e. some benzodiazepines and the more recently launched 'Z'-compounds, i.e. zopiclone, zolpidem and zaleplon. Large-scale surveys consistently report increases in the frequency of falls and hip fractures when hypnotics are used in the elderly (2-fold risk). Benzodiazepines are the major class of hypnotics involved in this context; falls and fractures in patients taking Z-compounds are less frequently reported, and in this respect, zolpidem is considered as at risk in only one study. It is important to note, however, that drug adverse effect relationships are difficult to establish with this type of epidemiological data-mining. On the other hand, data obtained in laboratory settings, where confounding factors can be eliminated, prove that benzodiazepines are the most deleterious hypnotics at least in terms of their effects on body sway. Z-compounds are considered safer, probably because of their pharmacokinetic properties as well as their selective pharmacological activities at benzodiazepine-1 (BZ(1)) receptors. The effects of hypnotics on balance, gait and equilibrium are the consequence of differential negative impacts on vigilance and cognitive functions, and are highly dose- and time-dependent. Z-compounds have short half-lives and have less cognitive and residual effects than older medications. Some practical rules need to be followed when prescribing hypnotics in order to prevent falls and hip fractures as much as possible in elderly insomniacs, whether institutionalised or not. These are: (i) establish a clear diagnosis of the sleep disorder; (ii) take into account chronic conditions leading to balance and gait difficulties (motor and cognitive status); (iii) search for concomitant prescription of psychotropics and sedatives; (iv) use half the recommended adult dosage; and (v) declare any adverse effect to pharmacovigilance centres. Comparative pharmacovigilance studies focused on the impact of hypnotics on postural stability are very much needed.

Separation and identification of zaleplon metabolites in human urine using capillary electrophoresis with laser-induced fluorescence detection and liquid chromatography–mass spectrometry

A capillary electrophoresis (CE) method using laser-induced fluorescence (LIF) detection for the determination of the hypnotic drug zaleplon and its metabolites in human urine could be developed using carboxymethyl-beta-cyclodextrin as a charged carrier. By the help of a complementary HPLC method coupled to mass spectrometry, three metabolites present in human urine could be identified as 5-oxozaleplon, 5-oxo-N-deethylzaleplon and 5-oxozaleplon glucuronide. N-Deethylzaleplon, a previously described zaleplon metabolite, as well as zaleplon itself could not be detected in human urine by the CE-LIF assay. The results were confirmed by spiking with reference compounds of the phase I metabolites. The metabolites differed very much concerning their fluorescence intensities, thus the 5-oxo metabolites present as lactam tautomer fluoresced tenfold lower than the unchanged drug zaleplon and its N-deethylated metabolite. The glucuronide of the 5-oxozaleplon, however, showed high fluorescence due to its lactim structure. Limits of quantification yielded by the CE-LIF assay including a ten-fold preconcentration step by solid-phase extraction were 10 ng/ml for zaleplon and N-deethylzaleplon and 100 ng/ml for 5-oxozaleplon and 5-oxo-N-deethylzaleplon.

Is there a rationale for prescription of benzodiazepines in the elderly? Review of the literature

Benzodiazepines (BZDs) constitute the most widely used symptomatic treatment of insomnia and anxiety. Many of these drugs are associated with adverse effects, such as daytime sedation and dependence with continued use. There is a concern about the rationale for and extent of benzodiazepine (BZD) use in the elderly. The sedation due to BZD use is a main risk factor for falls and other accidents. Impaired cognitive function with continuous use appears to be a major side effect. There is a general awareness that BZD use is inappropriate in many patients, and therefore discontinuation should be recommended whenever possible. Moreover, long-term use of these drugs should be actively discouraged. Although no unanimous recommendations concerning the optimal duration of the withdrawal process exist, BZDs may easily be withdrawn during a short period in most patients who are habituated to a low dose, if an initial phase with dose reduction and psychological support are provided. Alternative approaches involve sleep hygiene guidelines, behavioural treatment and psychotherapy tailored to the needs of the individual patient.