Sedative Hypnotics zaleplon

The nonbenzodiazepine sedative-hypnotics zaleplon, zolpidem, and zopiclone are replacing benzodiazepine sedative-hypnotics as first-line treatments for insomnia. Some antidepressants, such as sedating tricyclic antidepressants and trazodone, are also used as sedative-hypnotic agents for the treatment of insomnia. 

Kawashima K, Hosoi K, Naruke T, et al. Aldehyde oxidase-dependent marked species difference in hepatic metabolism of the sedative-hypnotic, zaleplon, between monkeys and rats. Drug Metab Dispos 1999 27 422-428. 

A class of sedative/hypnotic type drug that exert their effects through the benzodiazepine binding site on GABAa receptors. The class consists both of molecules that contain the benzodiazepine moiety, for example diazepam, lorazepam and flunitrazepam, and the newer, non-benzodiazepine compounds such as zolpidem, zopiclone, indiplon and zaleplon. BzRAs are primarily used for the treatment of anxiety, insomnia and to elicit varying levels of sedation. The wide selection of compounds currently available affords the prescribing clinician extensive options in terms of relative efficacies and durations of action. 

Pyrazolo[l,5-a]pyrimidine, the central scaffold in zaleplon, is present in 5, 6 and 7. Compound 5 inhibits the binding of tritiated benzodiazepine in synaptosomal fractions from rat cortex [20] and 6 and 7 inhibit the al GABAa subunit with K, — 53 nM and 17nM, respectively, and showed sedative-hypnotic action following i.p. administration to mice (<90% inhibition of motor activity)... 

One principal difference between the medications is half-life, that is, the time required to metabolize 50% of the compound present in the body. Zolpidem has a half-life of 1.4-4.5 honrs, zaleplon has a half-life of 0.9-1.1 hours, and eszopiclone has a half-life of abont 6 honrs. The key is the markedly shorter half-lives that are displayed by many other sedative-hypnotics, as shown in Eigure 9.1. Only eszopiclone has been shown effective for the long-term (np to 6 months) treatment of chronic insomnia. 

Nevertheless, sedative-hypnotic agents often play a useful role in treatment. In particular, by providing a successful night s sleep, these medications can break the cycle of anxious anticipation and dread that afflicts the insomnia sufferer during the night. We generally prefer using zolpidem or zaleplon as a first-line treatment for early-to-middle insomnia. Late insomnia often responds well to trazodone or eszopiclone, and trazodone often is a first choice in the presence of substance abuse for all insomnias. 

Timing of drug administration Take zaleplon immediately before bedtime or after going to bed and experiencing difficulty falling asleep. As with all sedatives/hypnotics, taking zaleplon while ambulatory may result in short-term memory impairment, hallucinations, impaired coordination, dizziness, and lightheadedness. 

Respiratory ejects Although preliminary studies did not reveal respiratory depressant effects at hypnotic doses of zaleplon in healthy subjects, observe caution if zaleplon is prescribed to patients with compromised respiratory function because sedatives/hypnotics have the capacity to depress respiratory drive. Depression As with other sedative/hypnotic drugs, administer zaleplon with caution to patients exhibiting signs or symptoms of depression. Suicidal tendencies may be present in such patients and protective measures may be required. Intentional overdosage is more common in this group of patients therefore, prescribe the least amount of the drug that is feasible for the patient at any one time. 

Zaleplon (Sonata) [C IV] [Sedotive/Hypnotic] Uses Insomnia Action A nonbenzodiazepine sedative/hypnotic, a pyrazolopyrimidine Dose 5-20 mg hs PRN -1- w/ renal/hepatic insuff, elderly Caution [C, /-] w/ mental/ psychological conditions Contra Component allergy Disp Caps SE HA, edema, amnesia, somnolence, photosens Interactions t CNS depression W/ CNS d es-sants, imipramine, thioridazine, EtOH X effects W/ carbamazepine, phenobarbital, phenytoin, rifampin EMS Concurrent EtOH can t adverse CNS effects OD May cause profound CNS depression symptomatic and supportive Zanamivir (Relenza) [Antiviral/Neuramidase Inhibitor] Uses Influenza A (including HlNl swine flu) B Action X Viral neuraminidase Dose Adults Feds > 7 y.2 inhal (10 mg) bid for 5 d initiate w/in 48 h of Sxs Caution [C, M] Contra Pulm Dz Disp Powder for inhal SE Bron-chospasm, HA, GI upset EMS Does not reduce risk of transmitting virus monitor for bronchospasm or other severe resp events OD May cause resp problems s5rmptomatic and supportive... 

Noguchi, H., Kitazumi, K., Mori, M., and Shiba, T. (2002) Binding and neuropharmacological profile of zaleplon, a novel nonbenzodiazepine sedative/hypnotic. Eur ] Pharmacol 434 21—8. 

Several drugs with novel chemical structures have been introduced more recently for use in sleep disorders. Zolpidem, an imidazopyridine, zaleplon, a pyrazolopyrimidine, and eszopiclone, a cyclopyrrolone (Figure 22-4), although structurally unrelated to benzodiazepines, share a similar mechanism of action, as described below. Eszopiclone is the (S) enantiomer of zopiclone, a hypnotic drug that has been available outside the United States since 1989. Ramelteon, a melatonin receptor agonist, is a new hypnotic drug (see Ramelteon). Buspirone is a slow-onset anxiolytic agent whose actions are quite different from those of conventional sedative-hypnotics (see Buspirone). 

The rates of oral absorption of sedative-hypnotics differ depending on a number of factors, including lipophilicity. For example, the absorption of triazolam is extremely rapid, and that of diazepam and the active metabolite of clorazepate is more rapid than other commonly used benzodiazepines. Clorazepate, a prodrug, is converted to its active form, desmethyldiazepam (nordiazepam), by acid hydrolysis in the stomach. Most of the barbiturates and other older sedative-hypnotics, as well as the newer hypnotics (eszopiclone, zaleplon, zolpidem), are absorbed rapidly into the blood following oral administration. 

Some sedative-hypnotics, particularly members of the carbamate (eg, meprobamate) and benzodiazepine groups, exert inhibitory effects on polysynaptic reflexes and internuncial transmission and at high doses may also depress transmission at the skeletal neuromuscular junction. Somewhat selective actions of this type that lead to muscle relaxation can be readily demonstrated in animals and have led to claims of usefulness for relaxing contracted voluntary muscle in muscle spasm (see Clinical Pharmacology). Muscle relaxation is not a characteristic action of zolpidem, zaleplon, and eszopiclone. 

Tolerance—decreased responsiveness to a drug following repeated exposure—is a common feature of sedative-hypnotic use. It may result in the need for an increase in the dose required to maintain symptomatic improvement or to promote sleep. It is important to recognize that partial cross-tolerance occurs between the sedative-hypnotics described here and also with ethanol (see Chapter 23)—a feature of some clinical importance, as explained below. The mechanisms responsible for tolerance to sedative-hypnotics are not well understood. An increase in the rate of drug metabolism (metabolic tolerance) may be partly responsible in the case of chronic administration of barbiturates, but changes in responsiveness of the central nervous system (pharmacodynamic tolerance) are of greater importance for most sedative-hypnotics. In the case of benzodiazepines, the development of tolerance in animals has been associated with down-regulation of brain benzodiazepine receptors. Tolerance has been reported to occur with the extended use of zolpidem. Minimal tolerance was observed with the use of zaleplon over a 5-week period and eszopiclone over a 6-month period. 

Insomnia is a common comorbid condition with depression, and frequently is made worse by antidepressants, particularly the SSRIs. When insomnia persists despite adequate evaluation and attempts to reduce it by other approaches, it is often necessary to use a concomitant sedative-hypnotic, especially a short-acting nonbenzodiazepine with rapid onset such as zaleplon or zolpidem. At times a benzodiazepine sedative hypnotic such as triazolam or temazepam may be necessary. If anxiety persists during the day and cannot be otherwise managed, it may be necessary to add an anxiolytic benzodiazepine such as alprazolam or clonazepam. Use of sedative-hypnotics and anxiolytics should be short-term whenever possible. 

The fundamental neurobiological importance of the GABA A receptor is underscored by observations that even more receptor sites exist at or near this complex (Fig. 8—20). This includes receptor sites for nonbenzodiazepine sedative-hypnotics such as zolpidem and zaleplon, for the convulsant drug picrotoxin, for the anticonvulsant barbiturates, and perhaps even for alcohol. This receptor complex is hypothetically responsible in part for mediating such wide-ranging CNS activities as seizures, anticonvulsant drug effects, and the behavioral effects of alcohol, as well as the known anxiolytic, sedative-hypnotic, and muscle relaxant effects of the benzodiazepines. 

The newer sedative-hypnotics that are not benzodiazepines are rapidly becoming the first-line treatment for insomnia. These agents not only have pharmacodynamic advantages over benzodiazepines in terms of their mechanism of action, but perhaps more importantly, pharmacokinetic advantages as well. Three nonbenzodiazepine sedative-hypnotic agents that are now available are zaleplon (a pyrazolopyrimidine), zopiclone (a cyclopyrrolone not available in the United States), and zolpidem (an imidazopyridine) (Figs. 8—28-8—30 Table 8—4). 

Zolpidem (Fig. 8—29). This was the first omega 1 selective nonbenzodiazepine sedative-hypnotic and rapidly replaced benzodiazepines as the preferred agent for many patients and prescribers. It has a somewhat later peak drug concentration (2 to 3 hours) and longer half-life (1.5 to 3 hours) than zaleplon. 

Nonbenzodiazepine ligands at benzodiazepine sites This is a variation on the theme of partial benzodiazepine agonists, as these agents act at the same or similar site as benzodiazepines but are not structurally related to them. Thus, the pharmacology of nonbenzodiazepines is that of a partial agonist, but their chemistry is different from that of a benzodiazepine. This is similar to the approach that novel sedative-hypnotics such as zaleplon and zolpidem have taken, and perhaps a less sedating nonbenzodiazepine partial agonist could hold promise for the treatment of panic disorder. 

Zaleplon has a pharmacological profile similar to benzodiazepines. Zaleplon is a full agonist for the benzodiazepine oq receptor located on the GABAa receptor ionophore complex in the brain, with lower affinity for the a2 and a3 subtypes. It selectively enhances the action of GABA similar to but more selectively than benzodiazepines. Zaleplon, although not benzodiazepine-like in chemical structure, induces sedative-hypnotic, anticonvulsant, and anticonflict effects via its binding to the central nervous system (CNS)-type benzodiazepine receptors [33-36]. 

Several drugs with novel chemical structures have been introduced recently. Buspirone is an anxiolytic agent that has actions different from those of conventional sedative-hypnotic drugs. Zolpidem and zaleplon, while structurally unrelated to benzodiazepines, share a similar mechanism of action. 

Heydorn WE (2000) Zaleplon - a review of a novel sedative hypnotic used in the treatment of insomnia. Exp Opin Invest Drugs 9 841-858... 

Diazepam is better indicated if insomnia is associated with daytime anxiety. Other benzodiazepines prescribed for insomnia include nitrazepam, flur-azepam, loprazolam, lormetazepam and temazepam. The non-benzodiazepine hypnotics zaleplon, zolpidem and zopiclone are not licensed for long-term use. The sedative antipsychotic promethazine hydrochloride is sometimes used to facilitate sleep, with a 25-50 mg recommended dose. Melatonin has proved effective for some clients, mostly in regulating the sleep/waking cycle. Although evidence of efficacy is limited, some clients use herbs such as valerian and chamomile. If Mr AB will finally be diagnosed with depression, a trial with an antidepressant will be indicated. 

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