The drug does not cause erections it enhances blood flow to the penis which allows for better filling of the penis with blood which allows some men to get an erection and enhances the erection in others. It may in some men delay ejaculation but it will not give you a semi permanent woodie.

I tried viagra because my friend wouldn't stay up in a condom. On the three occasions I used it I was hard as soon as I set eyes on the lady. They say it doesn't increase size but I think I was slightly bigger. On all three occassions we worked it for an entire hour and I could not "climax" and I was rock hard for the entire hour.  This could just be me, I don't mean to brag, but even when I masterbate it takes me a long time to "POP". Also as a side effect I got a bad headache each time. Overall it certainly does work but I wouldn't recommend using it unless your friend really does need it.

I use it recreationally on occasion to enhance performance.  It has advantages and disadvantages.

It makes the 1st erection come at the drop of a hat (she doesn't even have to bend over!) and a bit larger and I last longer.  Also, the 1st erection takes longer to subside.

It makes the second erection a bit easier to get.

Overall it makes you "feel" larger or more engorged because of enhanced blood flow to the region.

Side effects:   bad headaches and sometimes lethargy a few hours after a full dose.

Solution:   I don't need it, but when I do want to ensure the chance of multiple pops I use half a pill and take an advil at the same time to premedicate away the headache severity.  After the session I will sometimes take a second advil.

Apparently, the pharmaceutical giants are busy at work developing new versions of viagra-like drugs that won't give the common headache side effect and don't require a 1 hour premedication time course.