Zaleplon

Zaleplon (marketed under the brand names Sonata and Starnoc) is a sedative/hypnotic, mainly used for insomnia. It is a nonbenzodiazepine hypnotic from the pyrazolopyrimidine class.

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Chemistry

Pure zaleplon in its solid state is a white to off-white powder that has very low solubility in water as well as low solubility in alcohol and propylene glycol. It has a partition coefficient in octanol/water is constant (log PC = 1.23) when the pH range is between 1 and 7.

Pharmacology

Taken orally, zaleplon reaches full concentration in approximately one hour. It is extensively metabolised, into 5-oxo-zaleplon and 5-oxo-desethylzaleplon (the latter via desethylzaleplon), with less than 1% of it excreted intact in urine.

Zaleplon interacts with the GABA receptor complex and shares some of the pharmacological properties of the benzodiazepines. Although not a benzodiazepine, zaleplon can cause similar effects: anterograde amnesia (forgetting the period during the effects) as the most common.

Zaleplon is primarily metabolised by aldehyde oxidase, and its half-life can be affected by substances which inhibit or induce aldehyde oxidase.

A meta-analysis of randomised controlled clinical trials which compared benzodiazepines against Zaleplon or other Z Drugs such as zolpidem, zopiclone has found that there are few clear and consistent differences between Zaleplon and the benzodiazepines in terms of sleep onset latency, total sleep duration, number of awakenings, quality of sleep, adverse events, tolerance, rebound insomnia and daytime alertness.^[1]

Zaleplon has a pharmacological profile similar to benzodiazepines, that is characterized by an increase in SWDS with rapid onset of hypnotic action. Zaleplon is a selective full agonist for the benzodiazepine omega1 receptor located on the GABA_A receptor ionophore complex in the brain. 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 by its binding to the central nervous system (CNS) type benzodiazepine receptors. The elimination half life of zaleplon is 1 hour irrespective of dose. Absorption is rapid. Zaleplon can be classed as an ultra short acting sedative hypnotic drug for the treatment of insomnia characterised by difficulty in falling asleep. Zaleplon increases EEG power density in the delta frequency band and a decrease in the energy of the theta frequency band. In tests on rabbits zaelplon shows drowsy pattern of spontaneous EEG characterized by high-voltage slow waves and desynchronization of hippocampal theta waves and an increase in the energy of the delta frequency band on the spectral analysis of the electroencephalogram.^[2]

Side-effects

Zaleplon may cause hallucinations, abnormal behavior, severe confusion, day-time drowsiness, dizziness or lightheadedness, unsteadiness and/or falls, double vision or other vision problems, agitation, headache, nausea, vomiting, diarrhea or abdominal pain, depression, muscle weakness, tremor, vivid or abnormal dreams and memory difficulties or amnesia.

Zaleplon is habit-forming, meaning addiction may occur. Stopping this medication suddenly after prolonged or frequent use may cause withdrawal effects such as mood changes, anxiety, and restlessness.

Recreational use

Zaleplon (Sonata) has a relatively high potential to be abused. Often this use involves a different delivery method (insufflation) to induce effects faster.  

The side effects of zaleplon are greatly increased when taken improperly, especially retrograde amnesia - the inability to remember the time during which one was under the influence of the drug. Zaleplon is a nonbenzodiazepine drug, and research on other drugs in this class has indicated that their potential for abuse was far lower than that of benzodiazepine drugs, but that they still carried a risk higher than first believed. The study specifically mentions persons with prior substance abuse problems as individuals with a high risk for addiction to nonbenzodiazepine type drugs. ^[3]

References