Green’s Dictionary of Slang

(US prison/Hisp.) heroin.

1968		‘Sl. of Watts’ in Current Sl. III:2.
1974		Fuentes & Lopez Barrio Lang. Dict. 29: carga Heroin.
1985		‘Jennifer Blowdryer’ Modern English 58: carga (n): Heroin, usually used to mean a fix.
1992		Bentley & Corbett Prison Sl. 51: Carga Heroin.
1993		L. Rodríguez Always Running (1996) 131: There was nothing like it, this rush, and here I was on the edges of [...] this fellowship of la carga, so integral to ‘la vida loca’.
2001		ONDCP Street Terms 5: Carga (Spanish) — Heroin.