Date of Award

January 2015

Document Type

Open Access Thesis

Degree Name

Medical Doctor (MD)



First Advisor

Leora I. Horwitz

Subject Area(s)



Since the landmark Institute of Medicine report brought patient safety to the forefront of public concern, there has been intense effort to reduce medication errors in the hospital setting. One such method, medication reconciliation during transitions in care, is now standard practice. While many studies have explored contributory factors and consequences of medication reconciliation errors at hospital admission and hospital discharge, the role of therapeutic interchange, or the substitution of a chemically different but therapeutically equivalent drug for the one originally prescribed, on patients' medication regimens has not been adequately investigated. In fact, no study has examined the extent to which therapeutic interchange is employed in the hospital and the impact it has on unintentional medication reconciliation errors.

We analyzed data from a prospective, observational cohort study of patients 65 years or older admitted to a tertiary care hospital for acute coronary syndrome, heart failure, or pneumonia between May 2009 and April 2010 who were discharged home. We examined patients' medications from six commonly interchanged drug classes (ACE inhibitors, ARBs, H2 blockers, inhaled corticosteroids, PPIs, and statins) and measured the frequency of therapeutic interchange at hospital admission, the rate of suspected errors associated with therapeutic interchange at admission and at discharge, and the role of therapeutic interchange on drug changes at discharge.

We analyzed 555 admission medications taken by 303 patients that were within the six drug classes of interest. Of these, 244 (44.0%) were therapeutically interchanged during hospitalization while the remaining medications were continued or held. We identified 78 (32.0%) therapeutically interchanged medications with suspected errors made at time of interchange. At discharge, a total of 41 (7.4%) of the 555 medications of interest had a suspected medication reconciliation error at discharge. 28 of these were medications that were therapeutically interchanged at admission, giving a relative risk of suspected error of 2.75 (95% CI 1.45-5.19) compared to medications that were not interchanged. 28 of the 244 therapeutically interchanged medications (11.5%), as compared to 8 of the 311 non-therapeutically interchanged drugs (2.6%), were switched at discharge to a different medication within the same drug class as the patient's original home medication (RR 4.46, 95% CI 2.07-9.61).

Therapeutic interchange during hospitalization is a common practice associated with a significant number of potential errors at admission and at discharge, creating a risk for patient misunderstanding and adverse drug events. In light of these findings, methods for safely practicing therapeutic interchange should be developed to improve patient safety.


This is an Open Access Thesis.

Open Access

This Article is Open Access