Pegstim Injection Pegstim contains Pegfilgrastim Injection, a long-acting granulocyte colony-stimulating factor (G-CSF) used to reduce the risk of infection in patients receiving myelosuppressive chemotherapy. It works by stimulating the bone marrow to produce neutrophils, a type of white blood cell that helps fight infections. Pegstim is commonly used in supportive cancer care to manage chemotherapy-induced neutropenia and should be administered under the supervision of a healthcare professional.