Opiate addicts use opiates to feel euphoria and/or control pain. But, as they continue to abuse opiates, their body becomes more and more tolerant to the effects. Thus, an addict will continue to take more and more of the opiate to achieve the same feeling of euphoria or pain control. Most people that overdose on opiates do so by taking too much of the opiate and overdose (typically, respiratory failure). If an overdose patient gets to the hospital in time, the effects of the overdose can be reversed with an injection of naltrexone. This blocks the neuroreceptors from getting the opiate and reversing the effects of the opiate overdose.