This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Opioid-Related Disorders, Subject name: Psychiatry
Naltrexone is used in opioid addiction because 
Select and explain. 
A. To treat withdrawal symptoms, B. To treat overdose of opioids, C. Prevent relapse, D. Has addiction potential
C: Prevent relapse
Answer: C: Prevent relapse 
Explanation: Ans. is 'c' i.e. prevent relapse Naltrexone is a pure opioid antagonistIt is a competitive antagonist at all opioid receptors.It can be used orally, to assist in the rehabilitation of ex-opioid abusers who are fully withdrawn (otherwise it will induce an acute Withdrawl syndrome).A patient who then takes an opioid, fails to experience the kick or euphoria because of the opioid antagonistic actions of the Naltrexone.