Can one doctor give out information about a patient to another doctor?

One of my doctors, a psychiatrist, at UCLA learned that I was under the the care of a cardiologist at UCLA through the school's internal network and immediately became concerned that a particular medication that he prescribed for me might be problematic to the condition for which I might be seeing the cardiologist about. I understand the concern and respect it. However, I don't want the cardilogist to know that I had been taking the medication in question, as I hadn't been telling him about it. Can the psychiatrist contact my cardiologist with that information without my permission? Thanks.