How can I explain this to my boss?

Ask him to please ignore the fb message

You're on FB with your boss? Bad idea.

You lie or tell the truth about being on drugs. Your choice.

PS: Lying will likely not work and you'll look horrible in front of your boss.

When my dad was in the hospital and they gave him Ambien, he started wandering around. Explain to your boss and stop taking it.

Your only hope is being completely honest. To be honest, if you were frustrated and wrote it, and then decided you spoke too soon and you don't want to quit, don't make up some stupid story about sleeping pills being to blame. Be honest.

The problem is, if it's honestly that you blacked out from ambien and had no idea what you were doing, you're admitting to being mentally disabled because of medication. I'd rather say I was PO'd, and regretted it, I'm sorry, and please forgive me.

Don't follow the advice to make up some stupid story. People aren't as dumb as you think they might be.

The people who are saying tell them the truth or find a new boss have a point, but if you’re in a desperate situation, tell them that a major event in your life happened and your judgement was clouded. Like a family member or friend died and you felt like you couldnt go on, or something like that. After a good nights sleep you came to your senses and felt like you might be okay

Gonna be hard to explain and your job may be at risk regardless if you were under the influence and not aware of what you were doing, your boss will surely think you are unstable for taking Ambien if it affects you that way. Were you drinking too? It doesn't look good!!!

Nothing. Need to find a new boss.

Tell him the truth. Exactly the truth.