Caelyx, also known by its generic name doxorubicin hydrochloride, is a form of chemotherapy medication used in the treatment of various cancers, including ovarian cancer, multiple myeloma, and Kaposi's sarcoma among others. It belongs to a class of drugs known as anthracyclines, which work by interfering with the DNA of cancer cells, preventing them from dividing and growing. Caelyx is distinct from traditional doxorubicin due to its encapsulation in liposomes, tiny vesicles that encapsulate the drug, allowing for a more targeted delivery to cancer cells and potentially reducing some of the side effects associated with conventional formulations. This liposomal encapsulation also permits the drug to stay in the bloodstream for a longer period, enhancing its effectiveness against cancer cells. As with any chemotherapy drug, Caelyx can have significant side effects, and its use is carefully considered by healthcare professionals based on the individual patient's condition and response to treatment.