Unintentional Therapeutic Errors Involving Insulin in the Ambulatory Setting Reported to Poison Centers

Background: Adverse drug events in the ambulatory care setting are not uncommon and can cause significant morbidity. Little research has been published on the management of adverse drug events involving insulin in the outpatient setting.
Objective: To analyze data on patients with unintentional therapeutic errors involving insulin managed by 9 regional poison control centers.
Methods: A retrospective search was performed for all records involving insulin at 9 poison centers, covering the population of 4 states for the years 2000–2009. A subgroup of the study population was selected with a reason for exposure of "unintentional—therapeutic error."
Results: There were 3819 insulin exposures reported, with an increase in the annual incidence of insulin exposures of 279% (from 170 to 645 patients/year) and a mean annual increase of 18%. Of the insulin exposures, 2584 were unintentional therapeutic errors (68%). The percentage of all insulin exposures that were unintentional therapeutic errors increased progressively, from 41% to 78%. There was a 495% increase in annual incidence of unintentional therapeutic errors involving insulin, with a mean annual increase of 28%. Unintentional therapeutic errors involving insulin occurred primarily in adults >40 years (73%), with 63% occurring in women. There was a pronounced increase in unintentional therapeutic errors involving insulin in the later evening hours, with 71% occurring between 1800 and 2400 and reaching a peak at 2200. The majority (n = 1803; 70%) of patients were managed in a non–health-care facility location, primarily their own residence.
Conclusions: This is the first report of an increasing trend of insulin-related unintentional therapeutic errors in the ambulatory setting. Our study highlights a number of striking features, including: (1) a consistent and dramatic increase of unintentional therapeutic errors involving insulin over the 10-year period, (2) a high incidence of unintentional therapeutic errors involving insulin in the late evening hours, and (3) a high incidence of unintentional therapeutic errors involving insulin involving adults >40 years and females. With their 24/7 availability, poison centers appear to be an increasingly important resource for patients experiencing unintentional therapeutic errors involving insulin.

Introduction

Adverse drug events in the ambulatory care setting are not uncommon and can cause significant morbidity.^[1–4]Insulin is one of the leading medications involved in adverse drug events leading to an emergency department visit, especially in older adults.^[2] However, the published data on insulin adverse drug events have focused primarily on the hospital setting.^[1–4] There is a lack of information on the epidemiology of insulin-associated adverse drug events in the ambulatory care or non–hospital-based setting. One study of a poisons unit in Germany found that 5% of insulin overdoses were accidental, and 90% of the cases were intentional suicidal insulin overdose, with all inquiries coming from the physician caring for the patient, suggesting these cases were not being managed in the ambulatory setting.^[5]

In the US, poison control centers are able to manage the majority of their patients in the ambulatory care setting, often reducing the need for an unnecessary emergency department visit. Poison control centers manage more than 200,000 adverse drug events annually, with 88% of these patients managed outside of the hospital setting.^[3,7] The real-time database of these centers would be a rich source of information on insulin adverse drug events in the ambulatory care setting. To date, no information has been published evaluating insulin adverse drug events in this setting. The objective of this study was to delineate characteristics and outcomes of unintentional therapeutic errors involving insulin, with a focus on cases in the ambulatory care setting.