Opiates such as heroin convert to morphine in the body which then activates opiate receptors located throughout the brain and central nervous system, including within the reward system.
Vicodin withdrawal typically begins within six to twelve hours of the last dose and symptoms may grow more intense over the next several days.
Opiates affect the limbic system, which controls emotions which can produce feelings of pleasure, relaxation, and contentment.
Opiate users spend the vast majority of their time obtaining opiates and recovering from its effects, give up other pursuits for the sake of drug use.