sedative

n. drug which causes calmness and relaxation, drug that reduces tension and anxiety

adj. calming, soothing, relaxing; anaesthetic, relieving pain and irritability (about a drug)

A sedative is a substance that depresses the central nervous system (CNS), resulting in calmness, relaxation, reduction of anxiety, sleepiness, and slowed breathing, as well as slurred speech, staggering gait, poor judgment, and slow, uncertain reflexes. Sedatives may be referred to as tranquilizers, depressants, anxiolytics, soporifics, sleeping pills, downers, or sedative-hypnotics. Sedatives can be abused to produce an overly-calming effect (alcohol being the classic and most common sedating drug). At high doses or when they are abused, many of these drugs can cause unconsciousness (see hypnotic) and even death.
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Sedative /sed·a·tive/ 1. allaying irritability and excitement. 2. a drug that so acts. sed·a·tive adj. [more]Sedative - Community and Resources

Noun
1. a drug that reduces excitability and calms a person
(synonym) sedative drug, depressant, downer
(hypernym) medicine, medication, medicament, medicinal drug
(hyponym) benzodiazepine
Adjective
1. tending to soothe or tranquilize; "valium has a tranquilizing effect"; "took a hot drink with sedative properties before going to bed"
(synonym) ataractic, ataraxic, tranquilizing, tranquilising
(similar) depressant

adj. sedative, calming, relieving pain and irritability (about a drug)