Oxycontin withdrawal symptoms vary and can be mild or severe, depending on how much and how long and individual has taken the drug.
Opiate addicted individuals need higher and higher amounts of opiates in order to prevent withdrawal symptoms and to maintain their feelings of euphoria.
When cocaine users stop using cocaine, or when they end a cocaine binge, they almost immediately feel the "crash" which includes depression, fatigue, lack of pleasure, anxiety, irritability, sleepiness and a strong craving for more cocaine.
On rare occasions, sudden death can occur on the first use of cocaine or unexpectedly thereafter. However, there is no way to determine who is prone to sudden death.