Personally I wouldn't give him anything. He may appear to be calmer if you give him sedatives, or similar, but he will still we aware mentally, and it could change his behaviour. I have 2 bitches in season at the moment, and I also have a male who is driving me mad ;-) so I really do sympathise.
If you know where the bitch is being walked I would walk your boy somewhere else, if possible, for the next few days.