This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

adj. tending to soothe or tranquilize

"Under proposed regulations, listed large predators can no longer be hunted in small areas, under tranquillising or narcotic immobilising agents, or if released in areas adjacent to a holding facility."

depressant   

tranquilizing