Used primarily in the medical field as an immunosuppressive agent, it plays a crucial role in preventing organ transplant rejection. It works by inhibiting the proliferation of T and B lymphocytes, which are essential for the immune response. This makes it effective in combination with other immunosuppressants in kidney, heart, and liver transplant patients. Additionally, it is sometimes prescribed for treating autoimmune diseases like lupus and psoriasis, where it helps to control the overactive immune system. Its hydrochloride form ensures better solubility and bioavailability, enhancing its therapeutic efficacy.