Hi, I have gone through your medical history carefully and understood your concerns. Doxazosin mesylate you ve been added to your actual therapy is an alpha-1 adrenergic blocker. It helps reducing high blood pressure. Unfortunately, sometimes, its use is associated with low blood pressure (bp), which is experienced with drowsiness, or fast heart beats. I think this is what you are experiencing now. I advise to monitor your bp for a few days, record the results to pass them to your doctor in order to change dosage or possible therapy. Make an appointment with your cardiologist and run cardiac tests: - EKG - echo cardiogram - Holter monitoring in order to determine the right diagnosis and further management. Hope this helps.