"I've had ongoing PTSD for the past 15 years, including nightmares almost every night. My neurologist finally started me on prazosin to see if it would help me get any sleep. I had to go up to 4mg to make the nightmares stop. I tried to go back down to 3mg but had nightmares so went back to 4mg. 

After 2 months at 4mg I'm back to not sleeping well and having nightmares 4-5 nights a week. I'm concerned that I will continue to build up a tolerance and it will become less effective. 

I did have one incident where I got up in the middle of the night and passed out, remaining unconscious for over 40 minutes. I have to really watch out for low blood pressure when taking any BP altering meds like this. A salty snack before bed seems to help."