I've had good luck with flexeril, but I take it for its more traditional use - as a muscle relaxer. I've never heard of it as a specific treatment for nightmares...but it makes sense to me. I take larger doses than mentioned here - 10mg 4 times a day, and it is prescribed by my regular doctor (as opposed to psychiatrist) to treat physical pain due to fibromyalgia.
I don't like how it makes me feel during the day; so I usually spread it out through the night because I am up and down so much.
I'm not sure how effective it is in terms of eliminating nightmares, but it definitely helps me sleep, and generally reduces the pain I feel the next day. My psychiatrist knows that I take it - it is in my chart - but he has never mentioned it in connection with PTSD. I'll have to ask him next time I see him.
*hodge: If this helps you to know - it makes me feel "icky." Lethargic, logy, groggy. All that fun stuff! I don't mind that feeling when I take it with other sleep meds but I don't take it during the day. I definitely wouldn't take one and then go drive somewhere. (Although apparently I can - people do - but I choose not to. I take other meds during the day.) I also have trouble with dry mouth but that is a side effect of many meds I take, and it is hard to separate the side-effects. But the logy feeling that I experience, that is definitely related to the flexeril.