Green’s Dictionary of Slang

Nembutal, a barbiturate.

1963		in T.I. Rubin Sweet Daddy 61: You know, get him sec – neb or dex or something.
1964		H. Selby Jr Last Exit to Brooklyn 39: Not even a nebbie. He could have given me one at least.
1972		B. Rodgers Queens’ Vernacular 141: neb (fr narc sI) nembutal.
2001		ONDCP Street Terms 15: Nebbies — Depressants.