Potentially Inappropriate Prescribing and Potential Clinically Significant Drug–Drug Interactions in Older Outpatients: Is There Any Association?

Background and Objectives: The purpose of the study was to determine the prevalence rate of potentially inappropriate prescribing (PIP), by using the Screening Tool of Older Person’s potentially inappropriate Prescriptions (STOPP) criteria in older outpatients, and its association with potential clinically significant drug–drug interactions (csDDIs). Materials and Methods: A cross-sectional study included 248 outpatients ≥65 years old divided into two groups depending on the presence of csDDIs. For estimating the clinical significance of csDDIs we used Medscape′s "Drug Interaction Checker". We applied the thirty PIP indicators from the STOPP criteria. Results: The presence of PIP (25.00%; all patients) was significantly higher in the group with potential csDDIs compared to the other group (43 vs. 19, respectively; Chi-square test, χ(2) = 9.947; p < 0.01). The most common PIP included the inappropriate use of proton pump inhibitors, long acting benzodiazepines, usage of thiazide diuretic in patients with gout, and duplication of therapeutic class. Patients with potential csDDIs had 43 potentially inappropriate medications (PIMs) prescribed. Out of this number, 12 (27.91%) PIMs were identified to participate in potential csDDIs. There was a correlation between the number of medications prescribed and the number of PIMs (ρ = 0.297; p < 0.01) and between the number of PIPs and the number of potential csDDIs (ρ = 0.170; p < 0.01). Conclusions: Older outpatients with potential csDDIs in relation to those with no potential csDDIs had significantly more prescribed drugs in total as well as inappropriate drugs. Almost 30% of these PIMs were included in potential csDDIs.