Taking the cayenne in caps could be the reason that you're getting nauseaus. Read the link below regarding why taking the caps is really not a very good idea. The link also includes some sugestions on how some folks have dealt with the cayenne including one very well thought out way to do it if you must take it in caps.
Theres also the shot glass method before drinking the lemonade that has been discussed here recently.
The book states 1/10th tsp or to taste. You can start slowly and build up to what you can handle. I had problems at the begining cause it was too hot for me but not being one to whine I grinned and beared it and by the 3rd day I was fine. As a matter of fact I even started liking it and have added a little more than the recomended amount.