Baclofen
"After using 20 mg in evening...I was getting no relief from muscle spasms, so I spaced dose out to 20mg in afternoon and 20 mg at evening As I got sleepy and dozed off in my chair, I found myself waking, but not breathing, I would have to gasp for a large amount of air and wake up... This went on all evening  This has never happened in my life before,   I repeated this a few days later and same results  OPEN MY EYES AND REALIZE I,M NOT BREATHING AND GASP FOR AS MUCH AIR AS I COULD TAKE.....VERY SCARY."