The recreational drug speedball that several writeups here describe may actually consist of any powerful stimulant and any powerful depressant. It is usually injected. Taking the two drugs together may seem counterproductive, but in fact both stimulation and relaxation are complex phenomena. The depressant relieves the jitteriness and physiological symptoms like clenched teeth and racing heart without nullifying the stimulant's emotional effects. It also cushions the crash.

The incomplete overlap between areas of effect also makes speedballs very dangerous. The reason is that many stimulants do not effect the respiratory depression effects of depressant drugs. Usually, if a given dose of depressant will make you stop breathing, a lesser dose will knock you into a stupor. But the stimulants can keep you awake and able to administer more drug right up to the point of overdose. Combine this with the impaired judgement and sense of invulnerability that many people feel on cocaine or methamphetamine, and you can see the potential for disaster.