A mortality index for postmarketing surveillance of new medications

The rate of introduction of new pharmaceuticals is growing as a result of advances in molecular pharmacology and targeted drug development. The Fatal Toxicity Index (FTI) has been proposed as a means for monitoring drug toxicity through post-marketing surveillance. The FTI requires data regarding the general availability of a particular agent in the community which, in the US, is proprietary. The authors propose a Mortality Index as an alternative method for calculating relative lethality that does not rely on proprietary information for postmarketing surveillance. Using data from the Toxic Exposure Surveillance System (TESS) a Mortality Index was calculated from the proportion of deaths occurring among all patients who present to a health care facility with an overdose on the same agent or class of agents. The average Mortality Index for various drugs or drug classes for the years 1989 to 1997 is reported. Because the Mortality Index for desipramine appeared much greater than that for the other tricyclics, a chi-squared analysis was performed. The authors conclude, based on this analysis, that desipramine is significantly more likely to lead to death after overdosage than any other tricyclic antidepressant in the study. Also, the Mortality Index appeared to identify the impact of pediatric formulations on overdose lethality. We conclude that the Mortality Index may be a useful tool for determining the safety of agents during the postmarketing surveillance phase.