Alprostadil
"Now been using for 2 months, 24 injections into treatment.
I've found that if not careful with the injection site ,it can cause pain for up to an hour and a less than satisfactory result.
HOWEVER, pay close attention and inject as instructed. If not deep enough it can be painful and cause bruising. I found that 3 o'clock and 9 o'clock and close to base of penis works flawlessly.  I still praise this med. Works great!"