Question 1: To what extent does re-prescribing and re-dispensing of culprit drugs contribute to the burden of adverse drug events presenting to Canadian hospitals?
Adverse drug events are unintended and harmful events related to medication use. A prospective Canadian study published in 2008 found that 12% of visits to a Canadian tertiary care emergency department were the result of an adverse drug event. Of these, 36% required admission to hospital, and almost 70% were deemed preventable. Data from Australia indicate that among patients admitted to hospital for adverse drug events, 30% may constitute repeat events. A prospective Dutch study found that among patients admitted to hospital for adverse drug events, 27% of culprit drugs—those implicated in causing the adverse events—were re-prescribed within only 6 months. It is unknown to what extent re-prescribing and re-dispensing of culprit drugs contributes to the burden of adverse drug events presenting to Canadian hospitals. Canadian data is required to understand the rate of re-prescribing and re-dispensing of culprit drugs to design, evaluate and implement effective strategies for prevention.
In their analysis, ICES Western used prescription data from Ontario Drug Benefits (ODB) records and hospital admission information from the Canadian Institute for Health Information Discharge Abstract Database (CIHI-DAD) and the National Ambulatory Care Reporting System (NACRS) for inpatient and emergency room admissions in Ontario, covering a 12-year timeframe.
Numerator: The number of re-prescribed or re-dispensed culprit drugs over the observation period. When numerous drugs are implicated in an adverse drug event, the re-prescription of the combination of drugs contributing to that event should not contribute to the numerator more than once, unless they are discrete events over time that can be taken into account in a time to event analysis.
Denominator: The total number of adverse drug events that are severe enough to either cause an emergency department visit or require hospitalization.
Sample: Minimum sample size of 100 adverse drug events in the denominator. Adult patients.
Timeframe: The analysis should include an observation period of at least six months after the occurrence of the adverse drug event, and how often a culprit drug was re-prescribed or re-dispensed over the period of observation.
Team bio: ICES Western is an interdisciplinary team of physicians, biostatisticians, and epidemiologists with a vision to create information that increases healthcare efficiency and improves patient safety.