What is the drug speed made of?

On the street "speed" is usually a generic term for either homemade or prescribed stimulant drugs of the amphetamine family (methamphetamine, dextroamphetamine, desoxyamphetamine, etc.) The most common "speed" is methamphetamine mainly because it is the only one that can be relatively easily produced illicitly by amateur chemists. Pharmaceutical-grade stimulants such as methylphenidate (Ritalin), which is quite potent, and modafinil are also referred to as speed but less commonly. Cocaine by itself is almost never called speed despite its unrivaled potency but when mixed with a powerful opiate such as heroin or morphine it yields the "speedball". Methylphenidate is also commonly used for this purpose.