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How long do the side effects of the Neulasta (pegfilgrastim) shot last?

Medically reviewed by Melisa Puckey, BPharm. Last updated on July 17, 2023.

Official answer


The clinical studies for Neulasta (pegfilgrastim) do not document how long the side effects of Neulasta last or when you would expect them to have stopped.

We do know that:

  • in the first 24 hours after the Neulasta injection peak median blood levels of approximately 70ng/ml are reached
  • by day 8 the median Neulasta levels have dropped to approximately 5ng/ml
  • over the second week Neulasta blood levels continue to reduce to a very low level.

Side effects from most medicines are more likely to occur when at the highest blood level, therefore, if this is the case, we would expect the side effects to be worse when blood levels peak at 24 hours. Then the side effects would decrease over the first week as Neulasta blood levels reduce, and then during the second week after Neulasta side effects would decrease even further.

With some medications side effects can be ongoing after all the medication has left the body, depending on how the medication has induced the side effect.

Related questions

What are the side effects of Neulasta?

The very common side effects of Neulasta are:

  • bone pain (up to 31%)
  • skeletal pain (up to 27%)
  • medullary bone pain (up to 26%)
  • spontaneously reversible mild to moderate lactate dehydrogenase elevations (up to 18%)
  • spontaneously reversible mild to moderate alkaline phosphatase elevations (up to 11%)
  • spontaneously reversible mild to moderate uric acid elevations (up to 11%)

For more information side effects of Neulasta click here: Neulasta side effects

Bottom line:

  • There is little information available from reliable sources about how long Neulasta side effects last.
  • Neulasta is a long lasting medicine, with peak levels achieved 24 hours after injection, levels drop considerably over the first 7 days and after 14 days there is only a small amount remaining in the body.

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