Severe drug interactions and potentially inappropriate medication usage in elderly cancer patients

Due to more comorbidities, polypharmacy is common in elderly patients and drug interactions are inevitable. It is also challenging to treat an elderly patient with a diagnosis of cancer. Prevalence and clinical impacts of drug interactions and using potentially inappropriate medications (PIMs) have been studied in geriatric patients. However, these are not well defined in oncology practice. The purpose of this study is to define the prevalence of PIMs and severe drug interactions (SDIs) in elderly cancer patients and investigate the factors associated with them.

Patients more than 65 years of age in both inpatient and outpatient clinics were evaluated. Patient, disease characteristics, and medications used were collected by self reports and medical records. Drug interactions were checked with Lexicomp® and PIM was defined with 2012 update of Beers criteria. Severe drug interactions are defined with category D or X DIs. Logistic regression was used to compute odds ratios (ORs) and 95 % confidence intervals (CIs) for the association between SDIs, PIMs, and clinical parameters.

Four hundered and forty-five elderly patients (286 outpatient, 159 inpatient), with a median age of 70 (65-89) were evaluated. SDIs were present in 156 (35.1 %) of patients, 81 (28.3 %), and 75 (47.2 %) for outpatient and inpatients, respectively (p < 0.001). PIMs were present in 117 (26.6 %) of the patients, 40 (14.2 %), and 77(48.4 %) for outpatient and inpatients, respectively (p < 0.001). In multivariate analysis; polypharmacy (≥5 drugs), inpatient status and diagnosis of lung cancer were associated with severe DIs. Polypharmacy, inpatient status, and bad performance score (ECOG 3-4) were associated with PIMs.

Nearly one third of the elderly cancer patients are exposed to severe drug interactions and PIMs. Clinicians dealing with elderly cancer patients should be more cautious when prescribing/ planning drugs to this group of patients. More strategies should be developed in this group of patients to minimize the medications prescribed and prevent severe DIs.