Prazosin is an α1 blocker medication primarily used to treat high blood pressure, symptoms of an enlarged prostate, and nightmares related to post-traumatic stress disorder (PTSD). It is a less preferred treatment of high blood pressure. Other uses may include heart failure and Raynaud syndrome. It is taken by mouth.Common side effects include dizziness, sleepiness, nausea, and heart palpitations. Serious side effects may include low blood pressure with standing and depression. Prazosin is a non-selective inverse agonist of the α1-adrenergic receptors. It works to decrease blood pressure by dilating blood vessels and helps with an enlarged prostate by relaxing the outflow of the bladder. How it works in PTSD is not entirely clear.Prazosin was patented in 1965 and came into medical use in 1974. It is available as a generic medication. In 2019, it was the 170th most commonly prescribed medication in the United States, with more than 3 million prescriptions. Medical uses
Prazosin is active after oral administration and has a minimal effect on cardiac function due to its α1-adrenergic receptor selectivity. When prazosin is started, however, heart rate and contractility can increase in order to maintain the pre-treatment blood pressures because the body has reached homeostasis at its abnormally high blood pressure. The blood pressure lowering effect becomes apparent when prazosin is taken for longer periods of time. The heart rate and contractility go back down over time and blood pressure decreases.
During an allergic reaction, the release of histamine from mast cells causes vasodilation which allows eosinophils to migrate from the blood and localize in affected tissues. Accumulation of eosinophils in tissues can be significantly damaging. Eosinophils, like other granulocytes, contain granules (or sacs) filled with digestive enzymes and cytotoxic proteins which under normal conditions are used to destroy parasites but in eosinophilia these agents can damage healthy tissues. In addition to these agents, the granules in eosinophils also contain inflammatory molecules and cytokines which can recruit more eosinophils and other inflammatory cells to the area and hence amplify and perpetuate the damage. This process is generally accepted to be the major inflammatory process in the pathophysiology of atopic or allergic asthma. Diagnosis
Diagnosis is by complete blood count (CBC). However, in some cases, a more accurate absolute eosinophil count may be needed. Medical history is taken, with emphasis on travel, allergies and drug use. Specific test for causative conditions are performed, often including chest x-ray, urinalysis, liver and kidney function tests, and serologic tests for parasitic and connective tissue diseases. The stool is often examined for traces of parasites (i.e. eggs, larvae, etc.) though a negative test does not rule out parasitic infection; for example, trichinosis requires a muscle biopsy. Elevated serum B12 or low white blood cell alkaline phosphatase, or leukocytic abnormalities in a peripheral smear indicates a disorder of myeloproliferation. In cases of idiopathic eosinophilia, the patient is followed for complications.