Will an ambien (zolpidem) that is 4-5 years old still work?

I'd Say Yes: A silly little secret is that a lot of medications far outlive their expiration dates (and probably many's lives). Not all, but many and I'd bet Ambien (zolpidem) is one of them. For sure, it won't be toxic to you. Generally if you keep a medication in a cool protected area out of light (like a refrigerator) it will be good for a long time.