150 Severe Drug Interactions (SDIs) and Potentially Inappropriate Prescriptions (PIPs) in Older Adults with Cancer

Background The objectives of this study were to identify the prevalence of severe drug interactions (SDIs) and potentially inappropriate prescriptions (PIPs) in older adults with cancer. Methods A 12-month prospective observational study of patients ≥65 years admitted to an oncology centre was conducted. SDIs were assessed using Stockley’s interaction checker; PIPs were identified using STOPP/START criteria. Logistic regression was applied to determine the influence of age, gender, co-morbidities and medication number on the likelihood of an SDI and a PIP. Results We enrolled 186 participants; mean age 72.5 (SD5.7) years, 46.2% female, mean co-morbidity number 7.5 (SD3.4), median medication number 7 (IQR4-9). Polypharmacy (≥6 medications) and major polypharmacy (≥11 medications) were identified in 60.8% and 17.7% respectively. Systemic anti-cancer therapies (SACTs) were concomitantly prescribed to 60.2%. SDIs were identified in 50.5% participants; 7.5% ≥1 SACT-SACT SDI, 41.4% ≥1 drug-drug SDI and 10.2% ≥1 drug-SACT SDI. The most common SDIs were beta-blocker/alpha-blocker (n=12), Selective serotonin re-uptake inhibitor (SSRI)/proton pump inhibitor (PPI) (n=11) and SSRI/Aspirin (n=8). A strong correlation between medication and SDI number was identified (r2=0.61, p-value <0.001). For each additional prescription, the odds of an SDI increased by 50.8% (Odds ratio 1.508, 95% CI1.288–1.764, p<0.001). PIPs were observed in 73.1%; median 2(IQR1-3). The most common PIPs were drugs prescribed beyond the recommended duration (46.8%), high-dose PPIs >8 weeks (34.9%) and regular opioids without laxatives (20.4%). Patients prescribed ≥1 PIP had more co-morbidities (8.4(SD3.4) vs 5.2(SD2.4), p< 0.001), a higher cumulative illness rating score (18(IQR12-20) vs 11(IQR10-14), p<0.001) and more prescribed medications (8(IQR6-10) vs 3(IQR1-4.25), p<0.001). For each additional prescription, the odds of receiving a PIP increased by 79.2% (Odds ratio 1.792, 95% CI1.459–2.02, p<0.001). Conclusion SDIs and PIPs are common in older adults with cancer and higher than previously reported. Comprehensive specialist medication evaluation, by a Geriatrician, may benefit patients.