A sedative or tranquilliser is a substance that induces sedation by reducing irritability or excitement. They are CNS depressants and interact with brain activity causing its deceleration. Various kinds of sedatives can be distinguished, but the majority of them affect the neurotransmitter gamma-aminobutyric acid (GABA). In spite of the fact that each sedative acts in its own way, most produce relaxing effects by increasing GABA activity.This group is related to hypnotics. The term sedative describes drugs that serve to calm or relieve anxiety, whereas the term hypnotic describes drugs whose main purpose is to initiate, sustain, or lengthen sleep. Because these two functions frequently overlap, and because drugs in this class generally produce dose-dependent effects (ranging from anxiolysis to loss of consciousness) they are often referred to collectively as sedative-hypnotic drugs.Sedatives can be used to produce an overly-calming effect (alcohol being the most common sedating drug). In the event of an overdose or if combined with another sedative, many of these drugs can cause deep unconsciousness and even death. Terminology
There is some overlap between the terms "sedative" and "hypnotic". Advances in pharmacology have permitted more specific targeting of receptors, and greater selectivity of agents, which necessitates greater precision when describing these agents and their effects:

Anxiolytic refers specifically to the effect upon anxiety. (However, some benzodiazepines can be all three: sedatives, hypnotics, and anxiolytics). Tranquilizer can refer to anxiolytics or antipsychotics. Soporific and sleeping pill are near-synonyms for hypnotics.
Franceschetti–Klein syndrome (also known as "mandibulofacial dysostosis") is a syndrome that includes palpebral antimongoloid fissures, hypoplasia of the facial bones, macrostomia, vaulted palate, malformations of both the external and internal ear, buccal-auricular fistula, abnormal development of the neck with stretching of the cheeks, accessory facial fissures, and skeletal deformities. : 577 It is sometimes equated with Treacher Collins syndrome. See also
Dysostosis

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