Postmarketing drug dosage changes of 499 FDA-approved new molecular entities, 1980-1999

Pharmacoepidemiol Drug Saf. 2002 Sep;11(6):439-46. doi: 10.1002/pds.744.


Purpose: Risks and benefits of marketed drugs can be improved by changing their labels to optimize dosage regimens for indicated populations. Such postmarketing label changes may reflect the quality of pre-marketing development, regulatory review, and postmarketing surveillance. We documented dosage changes of FDA-approved new molecular entities (NMEs), and investigated trends over time and across therapeutic groups, on the premise that improved drug development methods have yielded fewer postmarketing label changes over time.

Methods: We compiled a list of NMEs approved by FDA from 1 January 1980 to 31 December 1999 using FDA's website, Freedom of Information Act request, and PhRMA (Pharmaceutical Research and Manufacturers of America) database. Original labeled dosages and indicated patient populations were tracked in labels in the Physician's Desk Reference. Time and covariate-adjusted risks for dosage changes by 5-year epoch and therapeutic groups were estimated by survival analysis.

Results: Of 499 NMEs, 354 (71%) were evaluable. Dosage changes in indicated populations occurred in 73 NMEs (21%). A total of 58 (79%) were safety-motivated, net dosage decreases. Percentage of NMEs with changes by therapeutic group ranged from 27.3% for neuropharmacologic drugs to 13.6% for miscellaneous drugs. Median time to change following approval fell from 6.5 years (1980-1984) to 2.0 years (1995-1999). Contrary to our premise, 1995-1999 NMEs were 3.15 times more likely to change in comparison to 1980-1984 NMEs (p = 0.008, Cox analysis).

Conclusions: Dosages of one in five NMEs changed, four in five changes were safety reductions. Increasing frequency of changes, independent of therapeutic group, may reflect intensified postmarketing surveillance and underscores the need to improve pre-marketing optimization of dosage and indicated population.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Dose-Response Relationship, Drug
  • Drug Approval / statistics & numerical data
  • Drug Labeling / statistics & numerical data
  • Drug Utilization Review / statistics & numerical data
  • Humans
  • Product Surveillance, Postmarketing / standards*
  • Product Surveillance, Postmarketing / statistics & numerical data
  • Risk Assessment / statistics & numerical data
  • Survival Analysis
  • United States
  • United States Food and Drug Administration / standards*
  • United States Food and Drug Administration / statistics & numerical data