I can tell you what happens if one takes 230 mg of Ambien -- the most fabulously refreshing 8 hours of sleep that I've ever had! That wasn't a suicide attempt, I just really wanted to sleep so I took the remainder of the bottle after 10, 20, 30, and 40 mg didn't do a damn thing.
The LD50 in rats is something like 600 mg/kg, so it's exceptionally non-toxic. I've never actually heard of any death by Ambien OD, though I never looked for one.