Evaluation of discharge medication orders following automatic therapeutic substitution of commonly exchanged drug classes

Abstract

Objective: Automatic therapeutic substitution (ATS) is a mechanism that, upon patient hospitalization, prompts the pharmacist to exchange an equivalent formulary drug for a nonformulary medication, typically without prescriber contact. In facilities utilizing ATS, there is the possibility that physicians and patients may be unaware of the substitution, potentially leading to drug-drug interactions, therapeutic duplication, and/or increased patient expense following discharge should the original regimen not be resumed. The purpose of this study was to determine the frequency with which hospitalized patients subjected to an ATS protocol were not returned to outpatient drug therapy.

Methods: A retrospective chart review of adult patients admitted to an academic medical center between January 1 and June 30, 2011, was conducted. Patients were included if they were admitted on angiotensin-converting enzyme (ACE) inhibitors, antidepressants, nonsedating antihistamines, histamine (H2) receptor antagonists, or proton pump inhibitors (PPIs), and were then prescribed a different agent via ATS. Admission and discharge medication reconciliation documents, dictated discharge summaries, and patient education documentation reports were reviewed for drug therapies and doses, as well as medication counseling evidence. The primary endpoint was the percentage of patients not returned to original outpatient therapy following ATS. Secondary endpoints included prescribing events in patients not returned to original therapy, the rate and source of drug therapy counseling at discharge, and the number of patients discharged on a potentially cost-prohibitive drug, defined as any drug available only as a branded product during the study period.

Results: A total of 317 interventions were identified through review of pharmacy records. Of these, 47 patients (15%) were not returned to original outpatient therapy. Within this subsection, 15 patients (32%) were discharged on the substituted drug, eight patients (17%) resumed initial therapy but received a dosage adjustment from previous outpatient therapy, and three patients (6%) were discharged on a drug that was neither the substituted product nor the previous outpatient therapy. The remaining 21 patients had therapy discontinued (n = 12/47, 26%) or lacked documentation of discharge therapy (9/47, 19%). Nursing staff provided medication counseling to 288 of the 317 patients (91%). Overall, 51 patients (16%) were identified as receiving a cost-prohibitive drug.

Conclusion: Patients subject to ATS of commonly substituted drug classes were returned to their original outpatient drug therapy more than 85% of the time following inpatient hospitalizations, with similar rates of medication counseling at discharge. The prescribing of cost-prohibitive drugs has been identified as a potential area for pharmacist intervention at discharge.