I was just prescribed sildenafil 50mg for erectile dysfunction. most of the time i work out in the evening and consume a pre workout supplement. i plan to take the sildenafil when i return home from the gym. will this cause negative side effects?

You did not tell us the name of your "pre workout supplement". By my knowledge almost all pre-workout supplements on the market don't interact with sildenafil. Good luck!

Go to Drugs.com and enter everything you take including supplements. into their interaction checker and see. Your are young to need this. what did dr thing was the cause. I would worry about crap in the supplement being a problem. I assume you tole Dr exactly what your are taking.