Do NOT take opiates, including heroin or other prescription or illegal opiates while using naltrexone. Taking opiates with naltrexone increases your risk for an overdose, coma and death. Do not use naltrexone if you are dependent on opioids or if you are experiencing opioid withdrawal symptoms. Naltrexone should not be used before you complete a medically-supervised opioid withdrawal lasting at least 7 to 14 days.