Thank you very much... I appreciate your answer, and also understand that it is far better to euthanize at a vet's office. Unfortunately, where we live no vets work after 12:00 p.m. on Friday or during the weekend.
(You might consider moving to Northern Arizona!) Junior is not in pain now, and I think the Alprazolam and Oxycontin have helped. It will not be long now... I mostly wanted to know that those two drugs would not cause him convulsions or vomiting... he is pretty much unconscious now and we'll do the best we can.