Recovery of serum TXB₂ after aspirin withdrawal in healthy subjects. Following aspirin withdrawal in 48 aspirin-treated healthy subjects, the recovery of platelet COX-1 activity shows a 24- to 48-hour delay before linear increase of serum TXB₂. This delay is likely due to the degree of acetylation of bone marrow megakaryocytes and proplatelets. Adapted from Santilli et al⁶⁰  with permission.