This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
Opioid induced constipation is treated by 
Select and explain. 
A. Loperamide, B. Biperiden, C. Alvimopan, D. Naltrexone
C: Alvimopan
Answer: C: Alvimopan 
Explanation: Alvimopan, Naloxegal & Methyl naltrexone are peripherally acting opioid antagonists used to treat opioid induced constipation & paralytic ileus.