A client who received a renal transplant three months ago is readmitted to the acute care unit with signs of graft rejection. While taking the client's history, the nurse determines that the client has been self-administering St. John's Wort, an herbal preparation, on the advice of a friend. Which information is most significant about this finding?

C Ingestion of St. John's Wort can reduce the client's intake of sodium. B Adding the herb can decrease the need for corticosteroids. D The client probably used this herb to treat depression. A St. John's Wort can decrease plasma concentrations of cyclosporine.