Dog cancer: cbd tincture and prednisone contraindicationa

My 14 year old dog was just diagnosed with a mast cell tumor and he is very uncomfortable. At the crux of learning things for management, I have a bottle of pet cbd and a bottle of prednisone. I have read conflicting things about using the two together. He gets the prednisone in the morning (we are on day 2) but in the evening he definitely gets very uncomfortable and that's where the CBD comes in. What I need to know is can I give them both to him to manage symptoms until we know if his tumor is going to shrink in size to allow him to be more comfortable? Because as he is 14 It is not going to take me long to put him down over even moderate discomfort, but I do not want to do that without taking other people's experiences into consideration. Thank you in advance for your help Tweet