Can I give my 65 lb pit bull (2) 1mg xanax?

We took him to the vet the other day and they gave him Xanax 1mg and Clomicalm 80 mg. The Xanax says 1 pill every 12 hours as needed, especially prior to T-storms. and the Clomicalm says 1 pill once daily. It is storming right now and he is panting and whining back and forth and barking to go outside. I already gave him one of both at 5:35am but he has not calmed down.