MINIPRESS (Prazosin) is used with or without other medications to treat high blood pressure. Lowering high blood pressure helps prevent strokes, heart attacks, and kidney problems. Prazosin belongs to a class of medications called alpha blockers. It works by relaxing and widening blood vessels so blood can flow more easily. MINIPRESS can be used alone or in combination with other antihypertensive drugs such as diuretics or beta-adrenergic blocking agents. WARNINGS As with all alpha-blockers, MINIPRESS may cause syncope with sudden loss of consciousness. A Drug Widely Used to Treat PTSD Symptoms Has Failed a Rigorous Trial. Thousands of people with post-traumatic stress disorder have taken the drug prazosin to ease the nightmares and disturbances that stalk their sleep. Numerous studies have shown the drug to be effective at controlling those episodes. As with any drug, whether prescription or illicit, prazosin can produce psychotropic effects when abused. Its use can cause uncomfortable side effects, from lightheadedness and vomiting to fainting and depression. ... Still, the recreational use of prazosin can be dangerous.