I cannot prescribe drugs for an animal that I have not examined as that is very specifically prohibited by my veterinary licensing body.
However, I can tell you that in dogs I do use morphine to control pain.
You can read more about it HERE including dose:http://www.petplace.com/drug-library/morphine/page1.aspx
For a 73lb dog who I had examined, I would prescribe 50 to 105 mg of morphine in pill form to control pain. I would start at the low end, and wait 30 to 60 minutes to assess response, and then would add more if needed.
With the pill selection available, I would start with 60mg if he were my patient. I would wait 30 to 60min and then increase by 15mg every 30 min to a max dose of 105mg.
I hope that helps you!
My thoughts are with you and with your dog....
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The above is given for information only. Although I am a licensed veterinarian, I cannot legally prescribe medicines or diagnose your pet's condition without performing a physical exam. If you have concerns about your pet I would strongly advise contacting your regular veterinarian.