Doxepin
"I have suffered with severe anxiety and panic attacks, which manifested itself into not sleeping.  I literally stopped sleeping for several days.  Ended up in the ER a couple times and at the doctors all that week and finally had to be admitted to a mental health facility because nothing they were giving me was working.   I literally thought I was going to die.  After 9 days they finally found something that helped me sleep.   It was a combination of Doxepin 100mg, Xanax, Tramadol (which soon switched to Benadryl)  and Ambien.  These drugs gave me my life back and slowly restored my sleep cycle.  After a year or so I was weaned off the Ambien and then the Benadryl, so now I just take the Xanax & Doxepin (now lowered to 50mg).  Amazing."