Defining Treatment-Emergent Adverse Events with the Medical Dictionary for Regulatory Activities (MedDRA)


Summaries of safety data collected in a clinical trial typically include an analysis of the crude rate of treatment-emergent signs and symptoms. This paper outlines the issues in defining treatment-emergent events and discusses the impact of choosing different methodologies for event classification and data collection. It also relates these issues to the adoption of the Medical Dictionary for Regulatory Activities (MedDRA) as the standard coding dictionary for regulatory reports. While pharmaceutical companies are addressing the conversion of their existing dictionary system to MedDRA, it may be beneficial to address the issue of defining treatment-emergent so that any changes can be incorporated at the same time. Examples and recommendations are provided.

This is a preview of subscription content, access via your institution.


  1. 1.

    Chuang-Stein C. Safety analysis in controlled clinical trials. Drug Inf J. 1998;32:1363S–1372S.

    Article  Google Scholar 

  2. 2.

    Chuang-Stein C. Safety analysis: too much? not enough? and how? Biopharmaceut Report. 1992; 1(No.3):1–11.

    Google Scholar 

  3. 3.

    Gait JE, Smith S, Brown SL. Evaluation of safety data from controlled clinical trials: The clinical principles explained. Drug Inf J. 2000;34:273–287.

    Article  Google Scholar 

  4. 4.

    Tremmel L. Describing risk in long-term clinical trials. Biopharmaceut Report. 1996;4(2):5–8.

    Google Scholar 

  5. 5.

    O’Neill RT. Assessment of safety. In Biopharmaceutical Statistics for Drug Development. Peace KE, ed. New York, NY: Marcel Dekker;1988:543-604.

  6. 6.

    Offen W. Statistical evaluation of adverse events. In American Statistical Association Proceedings of the Biopharmaceutical Section. Alexandria, VA: American Statistical Association; 1988:1–6.

    Google Scholar 

  7. 7.

    Brown EG, Wood L, Wood S. The medical dictionary for regulatory activities (MedDRA). Drug Safety. 1999;20(2):109–117.

    CAS  Article  Google Scholar 

  8. 8.

    Goldstein DG, Wilson MG. Adverse event frequencies generate hypotheses of efficacy and safety. Clin Pharmacol Ther. 1993;54:245–251.

    CAS  Article  Google Scholar 

  9. 9.

    White CA. A preliminary assessment of the impact of MedDRA on adverse event reports and product labeling. Drug Inf J. 1998;32:347–362.

    Article  Google Scholar 

Download references

Author information



Corresponding author

Correspondence to Stephanie C. Koke MS.

Additional information

This work was sponsored by Eli Lilly and Company.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Nilsson, M.E., Koke, S.C. Defining Treatment-Emergent Adverse Events with the Medical Dictionary for Regulatory Activities (MedDRA). Ther Innov Regul Sci 35, 1289–1299 (2001).

Download citation

Key Words

  • Treatment-emergent
  • MedDRA
  • Adverse events
  • Preferred term
  • Lowest level term