The aim of this study was to assess the risk of hospitalization associated with the concomitant prescription of 10 highly prevalent drug-drug interactions (DDIs) among all individuals aged ≥65 residing in Bologna’s area, Italy. We used incidence density sampling, and the effect of current (last month) and past (≥30 days before) exposure to DDI was investigated through conditional multivariable logistic regression analysis.

Two DDIs were associated with increased hospitalization due to DDI related conditions: ACE-inhibitors/ diuretics plus glucocorticoids (current DDI: OR 2.36, 95% CI 1.94-2.87; past DDI: OR 1.36, 95% CI 1.12-1.65) and antidiabetic therapy plus current use of fluoroquinolones (OR 4.43, 95% CI 1.61-11.2). Non-Steroidal Anti-inflammatory Drugs (NSAIDs) increased the risk of re-bleeding in patients taking Selective Serotonin Reuptake Inhibitors (OR 5.56, 95% CI 1.24-24.9), while no significant effect was found in those without a history of bleeding episodes. Concomitant prescription of NSAIDs and ACE-inhibitors/diuretics in patients with a history of high-risk conditions was infrequent.

Within the pattern of drug prescriptions in the older population of Bologna’s area, we distinguished DDIs with actual clinical consequences from others that might be considered generally safe. Observed prescribing habits of clinicians reflect awareness of potential interactions in patients at risk.