My severely hyperactive child was prescribed Benadryl for this. It's been eight years now and we have finally been able to back off of it. It's rare now that she needs to have a Benadryl in order to go to sleep. She is still on the hyperactivity meds but I can see that being dialed back, too, in another year or two.
The Benadryl, though was life changing. For me, anyway. Before it was introduced I had to lay down next to her in bed and physically restrain her (I would wrap her in my arms) for between 30 and 60 minutes before she could calm down enough to go to sleep. One or two Benadryls about two hours before bedtime and she could lay down in bed and go to sleep within a few minutes. They didn't make her sleepy (one would lay me out cold) but they got her into a condition where she could go to sleep.
Amazing stuff and it never would have occurred to me to use it if we hadn't seen a doctor. I saw the doctor, actually. I was in for my annual physical and the doc asked me about life in general and I told him what I had to do every night. He referred me/her to a psychiatrist and that was the best advice I had had in a long while. As my child bounced around the psychiatrist's office like a ball he said that she was the youngest patient that he had ever seen with this severe a case of hyperactivity. She was three years old at the time.
I used to think that the ADD/ADHD stuff was not real. I was wrong. It's very real. I still believe that ADD/ADHD is over diagnosed, that some children are put on meds that shouldn't be. But having had a severely hyperactive child of my own I can say without any doubt that there are kids out there for whom medication is the only answer. My daughter was completely and totally unable to sit still and listen to a story, watch a television show, or anything else that required even a modicum of patience.
When she got older we asked her what it was like to not be medicated. She said that it was like having thousands of voices screaming in her head...very confusing. The medication worked instantly and she was then able to have a normal life. When she is on the meds she is not dopey or goofy or drugged out, she is, instead, a normal child.
The Benadryl was the second part of the equation. It allowed her to go to sleep like a normal child. Without it she would be up until two or three in the morning every single night. Pretty hard to do well in school without proper rest.
Anyway, when anyone tells me that they have a child who won't go to sleep I recommend Benadryl without reservation. It's harmless to the child and it works.