I agree with all who said not to take Ambien with alcohol...that is a very risky combination.
Ambien is a very strange drug, at least for me. I never take it now because it's so unpredictable. Some nights I would take it and still be awake when the sun comes up....completely unaffected. Other nights I could take it an zonk out and get the best night of sleep imaginable.
The problem is sometimes I have a very odd reaction to that drug. My mind starts to race and I get visual hallucinations. I won't go in to detail on this, but trust me, very strange things happen. It used to really worry my family, so I quit using it. It's too bad, because when it works right, it's a wonderful drug. It's just so darned unpredictable for me. But that is just me. I know that Ambien is a wonderful drug for many people.
I guess the bottom line is this: Since a doctor didn't prescribe the Ambien to you, if you have a bad reaction and need to go to the ER, you're going to be in a bad situation because you're going to have to admit you are taking it without a RX. I'm not morally against sharing medications, I just wouldn't want to see you get into trouble, since Ambien is a somewhat risky drug.