Green’s Dictionary of Slang

(N.Z. prison) a Rivitrol tablet, a brand-name for Naltrexone, which counters the effects (good or bad) of opioid use.

1999		D. Looser ‘Boob Jargon’ in NZEJ 13 34: rivvie n. Rivitrol - a drug.
2001		D. Looser Boobslang [U. Canterbury D.Phil. thesis] 154/1: rivvie n. Rivitrol.