Today is day 3 of the full strength Champix. You work your way up to full strength over a week. Most common side effect is upset stomach and I have that. Next most common is drowsiness. Yesterday I got up at 5 am. By 9 am I couldn't keep my eyes open so crawled under the covers for a wee nap. That nap lasted 3 1/2 hours and wow did I sleep deeply! Both of those side effects should go away over the next week.