Does Nortryptaline Have Adverse Side Effects?

I was prescribed nortryptaline for stomach pain. I was planning on starting tonight but my sleep schedule for the next few nights is going to be very off. The time i go to bed will probably differ by a few hours each day and i am supposed to take it at bedtime. Is it okay to take it at a little different time each day (give or take a few hours) or should i wait a few days to start? Also, are the side effects all common side effects and is there any way to prevent them?