Zaleplon pharmacological effects

Three doses of zaleplon have been compared with placebo in outpatients with insomnia in a 4-week study (11). During week 1, sleep latency was significantly shorter with zaleplon 5, 10, and 20 mg than with placebo. The significant reduction in sleep latency persisted to week 3 with zaleplon 10 mg and to week 4 with zaleplon 20 mg. Compared with placebo, zaleplon 10 mg and 20 mg also had significant positive effects on sleep duration, number of awakenings, and sleep quality. Pharmacological tolerance did not develop with zaleplon and there were no indications of rebound insomnia or withdrawal symptoms after discontinuation. There was no significant difference in the frequency of adverse events with zaleplon compared with placebo. The authors concluded that zaleplon provides effective treatment of insomnia with a favorable safety profile. 

Zaleplon s onset time, time to maximal drug effect, and duration of action are shorter than with triazolam. Hence, despite its non-BZD structure and unique BZD receptor binding profile, its behavioral pharmacological profile is similar to that of triazolam ( 157). Like zolpidem, zaleplon in recommended doses decreases sleep latency with minimal effect on sleep stages. Thus, it differs from BZDs, which prolong the first two stages of sleep and shorten stages 3 and 4 REM sleep ( 158). 

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. 

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]. 

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