Patient description: A 57-year old farmer was diagnosed with Parkinson's disease a year ago. He experiences slowness of movement and tremors. His past medical history is significant for hypertension and hypercholesterolemia. He lives with his wife. They have three children. He used to be active with planting and taking care of their farm animals before his diagnosis. The patient complains of shaking and slow movement. He had difficulty entering through a door, as he was frozen and needed guidance to step in. His handwriting is getting smaller. He is on Levodopa and Trihexyphenidyl. He stated his medications help with shaking and slow movement. But he still has difficulty initiating movements, stiffness and slowness in general. He is an alert and cooperative man who doesn't have any signs of dementia. He doesn't smoke or use any illicit drugs.

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Post-Traumatic Headache Male and female Active-duty SMs or Veterans aged 18 or older who are in good general health History of blast and/or impact head trauma mTBI meeting Defense and Veterans Brain Injury Center (DVBIC) mTBI criteria. o Mild TBI is defined as an injury to the head causing at least one of the following: alteration in consciousness (for up to 24 hours after the injury), loss of consciousness (0-30 minutes), and/or post-traumatic amnesia (up to 1 day post-injury). If available, the Glasgow Coma Scale score must be 13-15, and head imaging findings (if imaging was performed) must be negative Frequent HAs that started within 3 months after a head injury or marked worsening (a two-fold or greater increase in frequency and/or severity) of pre-existing headaches within 3 months of head injury HAs either 1) must last 4 or more hours a day and reach a moderate to severe intensity at any point during the headache, or 2) may be of any severity or duration if the participant takes a medication or other agent in an effort to stop or treat a headache HAs meeting these must have been present on average at least 8 days per 4-week period, starting within 3 months after head injury and occurring by self-report for at least 3 months prior to the Initial Screening Visit. The 4-week HA frequency/severity must be confirmed during the Preliminary Screening Period Women of childbearing potential must agree to abstain from sexual relations that could result in pregnancy or use an effective method of birth control acceptable to both participant and the clinician prescriber during the study. Men are not required to use contraception during the study Participants must have English fluency sufficient to complete study measures  Participation in other interventional research History of penetrating head injury History of TBI more severe than mild by DVBIC A primary non migraine and/or tension-type HA disorder (for example hemicrania continua; cluster) that accounts for the majority of current symptoms HAs of any kind of moderate or severe intensity on an average of more than 4 days per month preceding the concussive trauma Acute or serious medical illness or unstable chronic medical illness (e.g., unstable angina, myocardial infarction within 6 months, congestive heart failure, clinically significant or concerning cardiac arrhythmias; preexisting hypotension [systolic blood pressure<110] or orthostatic hypotension [systolic drop >20 mm Hg after 2 min standing accompanied by lightheadedness], chronic renal or hepatic failure, or acute pancreatitis. The of potential participants having acute serious and/or chronic medical illnesses other than those listed will be evaluated on a case-by-case basis by a study physician, PA-C, or ARNP Use of prazosin or other alpha-1 antagonist (including but not limited to alfuzosin, doxazosin, silodosin, tamsulosin, terazosin) for any purpose in the 2 weeks prior to initial screen (P1) visit and prohibited throughout the study Allergy or previous adverse reaction to prazosin or other alpha-1 antagonist Active psychosis or psychotic disorder, severe depression (as determined per clinician prescriber judgment), severe psychiatric instability or severe situational life crisis (including evidence of being actively suicidal or homicidal) Meets Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) for any Substance Use Disorder except caffeine-related disorders, or tobacco-related disorders