On two occasions I took 400mg of butalbital and when I took the version with less Tylenol I felt dizzy and weird and when I took the version with more Tylenol I didn't. Maybe it's a tolerance issue but when I took this dose the first time I had been taking 100-159mg/day for probaly at least a month (?). Does Tylenol interfer with the actions of barbiturates (it seemed to on some other occasions too)? Or maybe there was some difference taking the dose with less Tylenol in the evening and the other in the morning?