Speedball (drug)

Speedball (also referred to as powerballing) is a term commonly referring to the (sometimes intravenous) use of cocaine with heroin or morphine (if intravenously, in the same syringe). The speedball can also be taken by insufflation. The original speedball used cocaine hydrochloride mixed with morphine sulfate, as opposed to heroin. The term can also be applied to use of pharmaceutical opioids, benzodiazepines or barbiturates along with stimulants. However, since opioids and sedative-hypnotics have different objective and subjective effects, stimulant-depressant mixtures are known by the slang term "set up" A cocktail of drugs containing an opioid can cause a strong physical dependence and withdrawal symptoms.

These mixtures are often more potent than the sum of their parts, through drug synergy; this is an effect that can and has been used clinically, such as Brompton cocktail, the caffeine content of many codeine and dihydrocodeine combination drugs, and the use of stimulants both to potentiate the opioid and combat somnolence caused by high and rapidly escalating doses.

Cocaine acts as a stimulant, whereas heroin/morphine acts as a depressant. Co-administration is meant to provide an intense rush of euphoria with a high that is supposed to combine the effects of both drugs, while hoping to reduce the negative effects, such as anxiety, hypertension, palpitations and other common side effects of stimulants and sedation/drowsiness from the depressant. While this is somewhat effective, as one drug (the CNS stimulant) triggers the sympathetic nervous system and the other (the CNS depressant) triggers the parasympathetic nervous system, the two systems that regulate the fight-or-flight and rest-and-digest responses, respectively, and simultaneous activity of the two pathways is what normally keeps one's body in natural homeostasis, there is an imperfect overlap in the effects of stimulants and depressants. Additionally, by suppressing the typical negative side-effects of the two drugs, the user may falsely believe they have a higher tolerance, or that they are less intoxicated than they actually are. This can cause users to misjudge the intake of one or both of the drugs, sometimes fatally.

...
Wikipedia