This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Substance abuse, Subject name: Psychiatry
Which of the following is used to maintain abstinence in alcohol dependence 
Select and explain. 
A. Naltrexone, B. Clonidine, C. Disulfiram, D. Naloxone
A: Naltrexone
Answer: A: Naltrexone 
Explanation: Naltrexone (oral opioid receptor antagonist) probably interferes with alcohol-induced reinforcement by blocking opioid receptors., helping in maintaining alcohol abstinence. Ref: Sho textbook of Psychiatry by Niraj Ahuja 7th editon, page 42. Disulfiram also helps in alcohol abstinence but through its unpleasant reactions to alcohol intake.