Could Rashes And Itching On The Back And Arms Be Due To Metoprolol?

My 87y/o mother was just hospitalized for CHF & a non ST change MI. Her heart was enlarged & had an ejection fraction of 25%. She was stabilized on meds, was transferred and an eluting stent was placed @ Johns Hopkins. She was started on Plavix w/a loading dose of 600mg on 2/5 prior to PCI & discharged 2/6/15 on 75mg daily along with ASA 81 mg. The other new medicine started was Metoprolol 12.5 mg twice daily. On 2/12 she began itching and by 2/13 she had hives (2 had a bluish tinge) and a severe rash to her back and both arms. What will be the best drugs to help with the rash and itching? Is Plavix the most likely culprit as her cardiologist suspects who she saw 2/13. It has been discontinued and Effetin will begin today.