I think some people react strangely to different meds. My husband can take a day time cold capusule and fall asleep almost after taking it. If I take one, I'm zooming for hours. After surgery for his Melanoma - his pain meds made him loopy, but not sleepy. I came home from lunch one day to check on him and he was standing over the stove making eggs - singing out loud and dancing around with the pan - hot grease splashing around everywhere. His wound site was on his arm. After witnessing that, I thought I would need some meds! I discovered he had had a bad morning and decided to take two of the prescription (which was the indicated dosage). I decided at that time that it would be best if I hid his meds - and gave them as needed.
Speak with his doctor. Let him know the side effects that the meds are having on him. There is so much out there to help, there is absolutely no reason he should be suffering from lack of sleep.