You can also try Tonic Water which contains Quainine.
There was a medicine called Legatrim on the market. My dad got cramps for years and his dr suggested trying legatrim. It fixed his cramps almost as soon as he took it. Active ingredient was listed as Quinine.
I read the label, and said 'quainine = tonic water', and so have been quaffing tonic water whenever I feel a cramp. That works for me.
Yes, when you exercise you gotta take the electolytes & lots of liquids - gatorade & such, but I find that if you start getting cramps even after taking these, or if you get a crmap and you want to get over it very quickly, tonic water works.
Sounds wierd, I know, but don't knock it until you try it.