This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Central Nervous system, Subject name: Pharmacology
Which of the following statements is FALSE about Naltrexone? 
Select and explain. 
A. Parenterally administered, B. Used to prevent relapse of heavy drinking, C. Long acting, D. Cause hepatotoxicity
A: Parenterally administered
Answer: A: Parenterally administered 
Explanation: Ref: KDT 6/e p467 *Naltrexone is chemically related to Naloxone and is a pure opioid antagonist. It is more potent than Naloxone. *It differs from Naloxone in being orally active and having a long duration of action (1-2 days) which is used to prevent relapse of heapy drinking. *Side effects are nausea and headache; high doses can cause hepatotoxicity.