Green’s Dictionary of Slang

(US drugs) heroin, esp. when it is injected or smoked when one is suffering from withdrawal symptoms.

1967		P. Thomas Down These Mean Streets (1970) 5: I heard the change in his voice. The cura was taking effect. He was like normal now that the drug was part of him.
1971		E.E. Landy Underground Dict. (1972).
1995		R. Ramos ‘An Ethnographic Study of Heroin Abuse by Mexican Americans in San Antonio, Texas’ on Texas Commission on Alcohol and Drug Abuse 🌐 ‘Appendix A: Gloss. of Tecato Argot’ La cura – Fix.
2001		ONDCP Street Terms 7: Cura (Spanish) — Heroin.