Filgrastim, sold under the brand name Neupogen among others, is a medication used to treat low neutrophil count.

[19] Filgrastim is a recombinant form of the naturally occurring granulocyte colony-stimulating factor (G-CSF).

[23] The most commonly observed adverse effect is mild bone pain after repeated administration,[24] and local skin reactions at the site of injection.

[18] Other observed adverse effects include serious allergic reactions (including a rash over the whole body,[25] shortness of breath, wheezing, dizziness, swelling around the mouth or eyes, fast pulse, and sweating), ruptured spleen (sometimes resulting in death),[26] alveolar hemorrhage, acute respiratory distress syndrome, and hemoptysis.

[18] G-CSF is a colony stimulating factor which has been shown to have minimal direct in vivo or in vitro effects on the production of other haematopoietic cell types.

Neupogen (filgrastim) is the name for recombinant methionyl human granulocyte colony stimulating factor (r-metHuG-CSF).

[18] In 2015, Sandoz's filgrastim-sndz (Zarxio), obtained the approval of the US Food and Drug Administration (FDA) as a biosimilar.

[35] It is highly similar to the reference product Neupogen (filgrastim), which has been authorized in various EU countries.

[35] Shortly after it was introduced, analyses of whether filgrastim is a cost-effective way of preventing febrile neutropenia depended upon the clinical situation and the financial model used to pay for treatment.