cluster headaches
"This medication is very sedating for me.  I cannot take so much as 1 mg during the day unless I want a nap.  I take 4 mg at night and get about 4 hours of deep sleep.  Then I wake up and the rest of the night is restless with very vivid dreams.  If I take more, I get leg/foot cramps.  When I tried to taper off of it, I got some intense jaw pain that I had never experienced before.  I believe it helps my daily headaches somewhat by working on muscle tension and jaw clenching at night, however I do believe there is some addictive property such that coming off of it can be difficult due to increased muscle tension.  The leg cramp side effect seems to be really rare, and not all people find it so sedating."