What is the term used when cocaine is combined with heroin?

The term used when cocaine is combined with heroin is "speedball." This particular combination is notable because it brings together a stimulant (cocaine) with a depressant (heroin), which can create a heightened state of euphoria due to the opposing effects of the two substances. Users may seek this combination for its intensely pleasurable effects, but it also carries significant risks, including increased potential for overdose, as the effects of one drug can mask the effects of the other.

The other terms provided, such as "cocktail," "mixer," and "fusion," do not specifically refer to the combination of cocaine and heroin. "Cocktail" is often used more generally to refer to any mixture of substances. "Mixer" might imply a combination but lacks a specific association with any drugs, while "fusion" is too vague in this context. Therefore, "speedball" accurately describes this dangerous practice in drug use.