It has the same effect for women as it does for men - it increases blood flow in the relevent part of the body, namely the clitoris. It will not increase anyones sexual appetite, but it will bring an increase of sensation and possibly enjoyment.
Hi! i have heard that viagra does wonnders for women especially those under the age of 25. it stimulates the clitoral region and is supposed to make penetration more enjoyable. But i woulnt reccomend it all the time!