Opiate addicted individuals need higher and higher amounts of opiates in order to prevent withdrawal symptoms and to maintain their feelings of euphoria.
Researchers have now linked long-term Ecstasy use to Parkinson's disease.
Intramuscular heroin injection produces a slower onset of effects, taking several minutes to feel the intense rush users experience.
The use of amphetamines presents risks in patients with narrow-angle glaucoma or anatomically narrow angles.