OBJECTIVES: Lack of communication between physicians during transitions of care, amongst other factors, limits the ability of traditional medication reconciliation to optimize drug management. Urine drug tests (UDTs) can objectively identify recently ingested substances and associated drug-drug interactions (DDIs) that pose risks of adverse drug events (ADEs). Patients facing increased risk of ADEs who underwent multiple UDTs throughout treatment were evaluated to determine the impact of drug monitoring on the number of DDIs detected and, implicitly, on risk of experiencing ADEs.

METHODS: This retrospective analysis compared patients’ UDT results longitudinally. Physician-ordered UDT results were evaluated for chronic pain and/or behavioral health patients. For each patient, an earlier reference test was compared to the final test during the study period to determine whether the number of DDIs identified at the earlier test was reduced by the last test. Whether patients experienced fewer DDIs over the study period was evaluated by age, polypharmacy status (≥5 substances detected in an included UDT), DDI severity (moderate/severe/contraindicated), and substance reduction status (yes/no). The substances most commonly involved in mitigated DDIs were reported.

RESULTS: Results from 4,328 patients were included. Patients experienced 1.96 DDIs, on average, at the reference test. Polypharmacy patients experienced more DDIs across all severity levels (2.47 vs 1.33). Overall, 1,920 patients had fewer DDIs at the final test. From these, 63.5% of moderate, 83.4% of severe, and 87.9% of contraindicated DDIs were mitigated. Polypharmacy patients had greater reductions in DDIs compared to non-polypharmacy patients (moderate: 1.73 vs 1.17; severe: 1.34 vs 1.09; contraindicated: 1.06 vs 1.03). Opiates and psychiatric medications were independently most commonly involved in mitigated DDIs.

CONCLUSIONS: Consistent DDI testing throughout treatment may help reduce DDIs through improved drug management. This, in turn, has the potential to improve clinical outcomes and decrease healthcare resource use associated with ADEs caused by DDIs.