Hypersensitivity (allergic) reactions are seen rarely with Alprolix and include: swelling, burning and stinging at the injection site, chills, flushing, itchy rash, headache, hives, low blood pressure, lethargy, nausea and vomiting, restlessness, a fast heartbeat, tightness of the chest and wheezing. In some cases these reactions can become severe.

Some patients taking factor IX medicines may develop inhibitors (antibodies) against factor IX, causing the medicine to stop working and resulting in a loss of bleeding control. Factor IX medicines can also potentially cause problems due to the formation of blood clots in the blood vessels.

For the full list of all side effects and restrictions with Alprolix, see the package leaflet.