NOEL and NOAEL: A retrospective analysis of mention in a sample of recently conducted safety pharmacology studies.

While the concept of adversity is certainly relevant to nonclinical SP studies, actual current practices appear to reflect a history which generally avoids toxicologically-oriented classifications such as NOAEL. Questions remain regarding the applicability of NOAELs to safety pharmacology studies, including, importantly, the specific circumstances under which such designations of adversity may be considered to add value to understandings of relative risk and risk mitigation in early human clinical trials.