Mustargen (generic: mechlorethamine) is a prescription medication used to treat certain cancers of the lungs, blood, and bone marrow.  Mustargen belongs to a group of drugs called alkylating agents, which works by slowing or stopping the growth of cancer cells in your body by affecting the strands of DNA of cancer cells. 

This medication comes in an injectable form and is given directly into a vein (IV), abdominal cavity, chest cavity, or lining of the heart by a healthcare provider.

Common side effects of Mustargen include nausea, vomiting, and diarrhea.