16.8: Sedatives and Hypnotics Drugs: Miscellaneous Agents

Sedatives and hypnotics encompass a wide range of substances, each with its unique mechanism of action, uses, and potential adverse effects.

Melatonin congeners like ramelteon (Rozerem) and tasimelteon (Hetlioz) selectively bind to melatonin receptors (MT1 and MT2) and thus mimic the actions of melatonin, a hormone that regulates sleep-wake cycles. Tasimelteon is primarily used for non-24-hour sleep-wake disorder, common in blind patients. They are also used to treat conditions like insomnia and jet lag. Adverse effects can include dizziness, headache, and daytime sleepiness.

Meprobamate (Miltown) is an anxiolytic that works by modulating GABA_A receptors. It is rarely used, as there are safer and more effective alternatives. It has been associated with side effects such as drowsiness, dizziness, and, in rare cases, thrombocytopenia.

Etomidate (Amidate) and propofol (Diprivan) are intravenous anesthetic agents used for inducing and maintaining anesthesia or sedation. They work primarily by potentiating GABA_A receptor activity. Their use can be associated with respiratory depression and hypotension.

Clomethiazole enhances GABAergic neurotransmission and has the same mechanism as traditional barbiturates. It helps manage alcohol withdrawal syndrome due to its sedative and anticonvulsant effects. However, it carries a risk of dependence and overdose.

Pregabalin (Lyrica) modulates calcium channels and GABA receptors. Dizziness is a common side effect.

Suvorexant (Belsomra) promotes sleep by blocking orexins, neurotransmitters involved in wakefulness. Side effects can include daytime sleepiness, headaches, and abnormal dreams.

Doxepin (Sinequan), a tricyclic antidepressant, treats insomnia by blocking histamine receptors and increasing the levels of norepinephrine. Its use can trigger anticholinergic side effects such as dry mouth (xerostomia), constipation, and urinary retention.

Ritanserin and Agomelatine (Valdoxan), serotonin-antagonizing agents, have insomnia as one of their side effects. They are being studied for their potential in treating various psychiatric disorders. Adverse effects can include nausea, dizziness, and abnormal liver function tests.

While these agents have proven helpful in managing several conditions, their use must be carefully monitored to mitigate the risk of potential adverse effects and dependence.

A variety of  CNS depressants are utilized as sedatives and hypnotics, each with distinct properties.

Melatonin congeners help treat insomnia and jet lag by mimicking melatonin's action in regulating sleep-wake cycles.

Chloral hydrate is used in pediatric medicine for its calming effects. Meprobamate, an anxiolytic, reduces brain activity to induce relaxation.

Etomidate and propofol are intravenous anesthetic agents, often used for induction and maintenance of anesthesia or sedation. They primarily act by potentiating GABA_A receptor activity.

Clomethiazole, too, acts by enhancing GABAergic neurotransmission and helps manage alcohol withdrawal syndrome.

Suvorexant, an orexin receptor antagonist, promotes sleep.

Doxepin, a tricyclic antidepressant, treats insomnia by blocking histamine receptors at low doses.

Pregabalin binds to calcium channels, modulating calcium influx and inhibiting excitatory neurotransmitter release.

Newer agents include agomelatine, a serotonin-antagonizing melatonin agonist,  and ritanserin, a serotonin antagonist.