What Are The Side Effects Of Vetoryl?

Hi, I have a 13-year Westie who was recently diagnosed with Cushings disease. She is on 30 mg of Vetoryl for about 2-months. Recent blood work shows that all is normal levels. However, my husband came home today and she was sleeping and visibly shaking in her sleep. She was difficult to rouse and disoriented when awakened however he offered her a treat and she was satisfied. This is not the first time that I have noticed the shaking, although I have felt it when picking her up or petting her, not such a visible thing as today. Her water drinking has been cut in half (8-10 bowls to 3-5 bowls a day) and doctor said that she still may have residual cortisol levels in her body---her prior readings were 4,000. Bloodwork taken 2-weeks ago show that she is not producing excessive levels so he said the medicine was doing its job. But, she still from time to time experiences panting. The shaking is new. Starting since she began the medicine and not sure if it is the cushings or the medicine. Help please?