Not sure brother. My only bad experience to me was my first time. Without knowing it, I am over sensitive to PGE-1. Which of course today is a great thing because a tiny miniscule amount, around 0.5mcg is enough for a full sex session of hard wood which makes it very cost effective.
However, my first time trying it I went with the minimum medical dose of 2.5mcg. Erection lasted 7 hours. The problem was, by the 4-5 hour mark the pain is unbearable. My dick was so hard, I could use it as a steel pipe. Sharp pains developed around the base and around the tip. Not a pain that you can suck it up and move on, is a pain that makes you sweat and clinch and it doesnt go away. By the 6 hour mark I wanted to saw that shit out of my body. Thats how bad the pain was. I started debating going to the ER but I wasn't sure which makes you anxious. Finally around the 7 hour mark slowly started subsiding.