This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Sexual Disorders, Subject name: Psychiatry
Which drug is used in intracavernous injection for erectile dysfunction? 
Select and explain. 
A. Epoprostrenol, B. Alprostadil, C. Sildenafil, D. Tadalafil
B: Alprostadil
Answer: B: Alprostadil 
Explanation: AlprostadilQ contains naturally occurring prostaglandin E and, hence has vasodilator action. It can be injected into corpora cavernosa or administered intraurethrally. The firm erection is produced within 2 to 3 minutes and may last for 1 hour. Other injectable medications for erectile dysfunction include: Papaverine Phentolamine