This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: AIIMS 2017, Subject name: Pharmacology
Which of the following drug can decrease the size of prostate? 
Select and explain. 
A. Tamsulosin, B. Sildenafil, C. Finasteride, D. Prazosin
C: Finasteride
Answer: C: Finasteride 
Explanation: In BPH, urinary obstruction is present because of increased size of prostate(static component). This is increased by spasm of urethra(dynamic component).To dilate urethra; alpha 1A receptor blockers like tamsulosin and silodosin are used. These provide the immediate symptomatic relief by treating the dynamic component.To decrease the size of prostate, 5 alpha reductase inhibitors are used which inhibit the conversion of testosterone to DHT(dihydrotestosterone). Drugs are dutasteride and finasteride. These drugs are given for long duration.