What Causes Drop In Platelet Count And Mouth Ulcers?

31 yo female platelets dropped to 14,000 with symptoms of mouth sores and bruising. Was taking Zantac, carafate, and one other med for probable ulcers. Has not had an endoscopic procedure. Was placed in hospital, dosed with prednisone and taken off zantac, other med but left on the carafate. Platelets responded to over 100,000 in a few days of being on prednisone. Pt. went home but returned for follow up blood draws which resulted in steadily ^ platelets. Pt. back on Zantac, and the carafate only. Now, a week later pt is back in hospital with platelets of 4,000. She did receive a last resort diagnosis of ITP which her mother also has. They did not find anything else to explain the drop in platelets. She is receiving platelets right now but I am wondering if the Zantac can cause this rapid of a drop? Reading side effects of Zantac platelet decrease is mentioned as a possible cause but so many medicines report so many side effects. So, what s happening?