We discuss the importance of comparator medicines in Arena International's 2023 Outsourcing in Clinical Trials handbook Our article entitled ‘Budgeting for Clinical Trials: The Importance of Comparator Medicines’ appears in the 2023 Outsourcing in Clinical Trials (OCT) handbook by Arena International. Due to the growing number of global trials, and their increasing complexity, as well as drug shortages becoming more prevalent, sourcing comparator drugs has become more difficu