50: Chemotherapeutics Overview

INTRODUCTION

Although overdoses of chemotherapeutics are infrequent, these events are of greater consequence than overdoses of many other xenobiotics because most chemotherapeutics have narrow therapeutic indices. This is evident from survey data from poison centers in the United States. From 1988 to 2010, the median annual number of people exposed to chemotherapeutics reported to US poison centers was about 1000. In the past 5 years, the number of annual exposures to these chemotherapeutics has steadily increased to slightly over 1500 (Chap. 136). These exposures represent about one per 1000 cases of exposures to pharmaceuticals, or one per 2000 cases of all exposures annually reported to US poison centers. Approximately two-thirds of the people exposed to chemotherapeutics in these reports were adults, one-fourth of the group was young children, and the remainder was adolescents. The annual trend for the proportion of exposures among adults and children appears to have remained at approximately 70% and 25%, respectively, from 2001 to 2010. Children and adolescents between the ages of 6 and 19 years accounted for approximately 7% of the population annually exposed, and this frequency did not change between these years. Although these differences among age groups can represent the incidence of cancer in these populations, further analysis is warranted to better define the reasons for these observations because they are not apparent.

Among single exposures to chemotherapeutics reported to US poison centers from 2006 to 2010, the annual percentage of unintentional exposures was slightly above 97%, and the annual percentage of exposures resulting in moderate or major severity in toxicity remained at approximately 6%. The mortality rate was about two per 1000 single exposures in this same period. These observations are consistent with a hospital-based survey and can be attributed to the increased toxicity of these chemotherapeutics.²⁴ The prevalence of the exposure to chemotherapeutics is expected to continue to increase because of the increased availability of oral formulations⁷⁶ and their expanding therapeutic indications.

MEDICATION ERRORS WITH CHEMOTHERAPEUTICS

The importance of understanding the occurrence of medication errors is to prevent future events of a similar nature. Fortunately, medical errors related to the use of chemotherapeutics occur infrequently. The reported medical error rate for the chemotherapeutics varies from 0.04% to 5.5% based on data from US medical centers,^13,22,24,71 although the true prevalence of these events remains unknown. The rates reported by international medical centers are similar.^{25,41,43,44,53,66} These reported estimates vary by the clinical setting (hospital vs. outpatient) and the patient population (adults vs. children). The outpatient setting and the treatment of children present several unique challenges to the health care system, including increased volumes, decreased control measures, increased workload, and unique dosing schemes such as dose based on body surface area.^24,69 In a satellite pharmacy setting, two of the potentially ...