A few times I have taken 1 50mg generic viagra, and didn't really notice anything different.
The other day this new girl I am seeing was on her way over, so I popped two 50mg viagras, and holy sh*t. I guess you can say human jackhammer is an understatement. But then about 6 hours later I got a really extreme headache, and I am not possitive but I assume it was from the viagras. So, for me, 100mg is the dosage needed to see something above normal.