Concomitant polypharmacy is associated with irinotecan-related adverse drug reactions in patients with cancer

Patients with cancer often receive chemotherapeutic agents concurrently with other medications to treat comorbidity. The practical effects of concomitant medications, especially polypharmacy, on adverse drug reactions related to irinotecan-based chemotherapy are not well documented. Associations of adverse drug reactions related to irinotecan monotherapy or a combination of irinotecan, 5-fluorouracil, and l-leucovorin (FOLFIRI) with concomitant medicines used to treat comorbidity were retrospectively investigated in Japanese patients with cancer. Of the 172 patients, 118 received concomitant medications. Twenty-one patients had grade 4 neutropenia and/or grade 3 or 4 diarrhea. Univariate and multivariate analyses revealed that concomitant medications were significantly associated with irinotecan-related severe neutropenia and/or diarrhea (P = 0.023 and 0.044). Multiple concomitant medications were significantly related to severe irinotecan-related toxicity in patients given monotherapy or FOLFIRI (P = 0.01). The incidence of severe irinotecan-related toxicities increased in parallel with the number of concomitant medications. We found that multiple concomitant medicines were significantly associated with severe irinotecan-related toxicity, indicating that polypharmacy must be effectively managed to decrease the risk of adverse drug reactions in patients with cancer who received irinotecan-based chemotherapy.