What will happen if you take lyrica (pregabalin) and excedrin pm together?

Fall asleep?: Excedrin PM has diphenhydramine which is known to increase certain side effect of Lyrica (pregabalin) such as dizziness, drowsiness, and difficulty concentrating. Nothing more serious. Of course, these side effects will not occur in everyone. Be careful operating dangerous or heavy machinery, etc. while under the influence. Best just to head to bed unless & until you know how the meds affect you, personally.