Green’s Dictionary of Slang

1. a barbiturate, a tranquillizer.

1968		‘Sl. of Watts’ in Current Sl. III:2 21: Downers, n. Barbiturates.
1970		E. Tidyman Shaft 156: The momentary relief of the uppers and the downers that they could swallow or smoke.
1981		J. Wambaugh Glitter Dome (1982) 161: Bookies don’t usually offer uppers and downers to their clients.
1992		I. Rankin Strip Jack 98: Don’t let her take too many downers.
1993		G. Disher Deathdeal [ebook] ‘[U]ppers, downers, some marijuana to sprinkle in my roll-your-own tobacco’.
2004		J. Ellroy ‘Hollywood Fuck Pad’ in Destination: Morgue! (2004) 242: He’s got pharmacy downers.
2010		J. Ellroy Hilliker Curse 30: Booze and downers fueled my great-writer fantasies.
2010		K. Richards Life 185: They’d put all their gear away, the downers, the Tuinals [Ibid.] 193: He really loved to take too many downers, Seconals, Tuinals, Desbutals, the whole range.
2021		C. Hammer Opal Country 206: ‘You name it, he’d swallowed it. Uppers, downers, opiates, analgesics’.
2023		R. Milward Man-Eating Typewriter 411: I had an array of uppers and downers — barbiturates [...] French Blues.

2. any drug used to reduce the unpleasant experiences that can accompany the end of using a given ‘up’ drug, e.g. crack cocaine.

1999

Africa News Service 29 Nov. 🌐 We would take whisky as a downer until someone told us that heroin was more effective.

3. heroin, as opposed to cocaine.

1997

Simon & Burns Corner (1998) 62: Dope is the downer, the heavy.

4. methadone.

2000

W.T. Vollmann Royal Family 632: I drank my homegirl’s methadone. You ever tried that shit? I don’t like them downers.