Try making you complete days worth of the lemonade without adding the cayenne. When you're ready to drink a serving of lemonade, pour it into a glass and add your cayenne right when you're ready to drink it. It's a lot easier to take that way. Not only that - but you might find that you can handle more of it - if you don't let it sit in your prepared lemonade all day.
The cayenne is important. It helps with elimination, circulation, etc... A lot of people around here increase the cayenne to as much as 1 teaspoon. It's just not that easy to take if you pre-mix it into a days worth of lemonade.