I agree w/ GuitarRox - doubtful this one-time deal would do you much harm. But same as GR, I'd want to know why you took Viagra in the 1st place at age 24 - were you experiencing any symptoms that made you think you were developing ED, or was this just sort of an 'experiment' to see what would happen? First, it's never a good idea to take a Rx drug that wasn't prescribed for you, and 2nd, it's an even worse idea to take a larger dose than prescribed.