Don't worry. Competent docs know what works best. Some will provide Valium to relax the patient and also stabilize BP. Trust me, if they administer Valium, you'll sleep just fine. There are other options too in case you have any known adverse effects from Valium.
Ultimately, a responsible Doctor will review your entire medical history and meds way in advance of your procedure. So taking other meds like the one you suggested can have a more detrimental effect on you without your knowledge, so please, please be careful my friend.
One of the things that I truly respect in my supporting docs is that they each consider one's past and current medical history "before" any final decisions are made.
Bottom line? Always, always consult your doctor in advance.