At the maximum they can have 1mg per pound, (most capsules are 25mg). So you gave 75mg for a 75lb dog which is the maximum for him and I think it is up to 3 times per day, or every 8 hours.
I think it's best to go with the least amount if and when possible. If he is sleeping at 12:30, continue to let him sleep and then give once he wakes up and shows signs of irritation. Which of course will just make for a rough night's sleep on your part....but with your Xanax you might not even hear the alarm!!! When hubby used to take that he wouldn't even know if the house was burning down around him.... I hope he feels better soon.
Susi & Cami