Green’s Dictionary of Slang

(US drugs) a vein shot, i.e. an intravenous injection of narcotics; a vein shooter n.

1938		D. Maurer ‘Lang. of the Und. Narcotic Addict’ Pt 2 in Lang. Und. (1981) 110/2: v.s. Var. vein-shot. 1. Narcotics injected intravenously. 2. A vein-shooter.
1949		Monteleone Criminal Sl. (rev. edn).
1959		J.E. Schmidt Narcotics Lingo and Lore.
2001		D. Looser Boobslang [U. Canterbury D.Phil. thesis] 198/1: VS n. = speed sense 1.