Is cytoxan (cyclophosphamide) a common drug used?

Yes: Used in breast cancer, lymphomas, sometimes myeloma, occasionally ovarian cancer. Probably one of the most common chemotherapy drugs used.

Yes, cytoxan (cyclophosphamide) is: A widely used drug, both in the oncology setting and to regulate immune system dysfunction by many subspecialists. It belongs to a class of drugs known as oxazophosphorines and acts as an alkylating agent. It should be used with caution. P characteristic side effect is hemorrhagic cystitis when given at high doses, and also carries a risk of secondary malignancies, especially myeloid leukemia.