Should Byetta Always Be Kept Under Refrigeration After Opening?

Hi. I have been using Byetta for a number of years. I always keep he pen refridgerated.I will be going on a cruise soon and keeping it refridgerated may be a problem.After the first use of the pen, does it still require refridgeration or can I keep it within a certain temp range on my person without a refridgerator?Thank you Bob S