My trazadone problem was similar, yet slightly different. I was prescribed trazadone for sleep at the same time I was prescribed zoloft for depression and OCD. The 25mg dose of trazadone didn't do much for me, so my doc said to try 50mg. At the same time, I told her the zoloft wasn't working out, because of side effects, so I was prescribed paxil.
On the paxil, I didn't need the trazadone for sleep. I couldn't stay awake as it was. I slept in some instances for almost 24 hours straight. When other, more problematic side effects started due to the paxil, I weaned myself off of it. Surprise suprise, I couldn't sleep again. So, being that 25mg and 50 mg of trazadone didn't help much before, and since the doc said to just increase the dose, I took 100mg to try and sleep.
I then got every bad side effect you'd imagine all at once. I still couldn't sleep, but now my heart was pounding, my head felt....odd...and I felt my nasal passages close up over a 5 minute period...I also felt my mouth go bone dry. All that mixed with the lovely withdrawl symptoms from the paxil and I did not have a good day.
After relaying all this to my doc, she made a brilliant suppostion -- "You might be sensitive to medication." You don't say.