AbstractBackgroundAL amyloidosis is associated with acquired factor X (FX) deficiency. Experience related to its management is limited to case reports and series using prothrombin complex concentrate, fresh frozen plasma, plasma exchange, recombinant activated factor seven, and desmopressin with limited and variable efficacy. FX concentrate has not been widely used in its management.Study Design and MethodsWe report our experience with the perioperative use of FX concentrate (Coagadex) in two patients with AL amyloidosis‐associated acquired FX deficiency requiring surgery, using their individual pharmacokinetic studies to manage perioperative hemostasis. Pharmacokinetic studies involved obtaining post‐infusion FX activity at 10 min, 2, and 4 h following the administration of FX concentrate to calculate the FX half‐life.ResultsBoth patients' plasma FX activity was successfully increased to provide perioperative hemostatic support. Monitoring FX activity post‐surgery was also utilized to maintain FX activity levels to prevent post‐operative bleeding.ConclusionPharmacokinetic studies have a useful role in tailoring preoperative FX repletion in patients with AL amyloidosis associated with acquired FX deficiency.