Most are products of modern chemistry. Their action in the body is usually more complex than that of alcohol. Sometimes a drug's effects may continue after it can no longer be detected in the blood. In other cases, a drug may be detected in the blood after its action has stopped. Illegal drugs are not the only ones that can impair your ability to ride a motorcycle.
Many prescription drugs have adverse effects on a motorcyclist's riding skills.
There has been a lot of study done on the effects of drugs on driving behavior, but not much relating to drug use to motorcycle accidents. As with alcohol, however, it can be easily assumed that the adverse effects of some drugs on driving behavior will be magnified when riding a motorcycle. Even a cold tablet can reduce vision, alertness and perception. Many affect both. These processes are important for all drivers, but even more so for motorcyclists.