Green’s Dictionary of Slang

cura n.

[Sp. cura, a cure]

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

[US]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.
[US]E.E. Landy Underground Dict. (1972).
[US]R. Ramos ‘An Ethnographic Study of Heroin Abuse by Mexican Americans in San Antonio, Texas’ on Texas Commission on Alcohol and Drug Abuse [Internet] ‘Appendix A: Gloss. of Tecato Argot’ La cura – Fix.
[US]ONDCP Street Terms 7: Cura (Spanish) — Heroin.