Background Cancer patients receiving chemotherapy may be at risk of drug interactions between antineoplastic agents and drugs prescribed in primary care, which can lead to an increase in the number and severity of adverse drug events or a reduction in treatment effectiveness.
Purpose To assess the incidence of potential interactions between chemotherapy drugs prescribed by oncologists in hospital care and any other drugs prescribed by general practitioners in primary care.
Material and methods Retrospective and observational study. Patients diagnosed with any type of cancer between 1st May and 30th September 2014 who received oral and intravenous chemotherapy were included. Data were obtained from two computerised order entry systems: Oncowin (hospital setting) and electronic medical history (Primary Care setting). Potential interactions were checked with Micromedex 2.0: minor (limited clinical effects), moderate (interaction may exacerbate the patient’s condition and/or require an alteration of treatment) and major (can lead to hospitalisation/death).
Results 340 patients. Median age 66 years old (28–89) [51.2% >65 years old, 39.1% 45–65 years old and 9.7% <45 years old]. 54.5% men. 1,634 revised drugs, 4.8 drugs/patient (13.8% of patients did not take medicine at home). Potential interactions detected: 67 in 49 different patients (14.4% of patients studied); 1.5% minor interactions, 22.4% moderate and 76.1% major interactions. Interactions detected were more frequent in metastatic setting (52.2%): 85.7% major and 14.3% moderate, followed by adjuvant treatment (19.4%) and neoadjuvant treatment (10.4%). Interactions were most frequent with erlotinib, paclitaxel, pemetrexed, methotrexate, capecitabine and pazopanib as cytostatic drugs and omeprazole, simvastatin, dexketoprofen and acetylsalicylic acid as usual drugs. Highest frequency of severe interactions was between erlotinib with proton pump inhibitors and NSAIDs (11.8% each).
Conclusion The vast majority of potential drug interactions are major and could be reduced by encouraging communication between the pharmacist, oncologist and primary care doctor.
Flockhart DA. Drug Interactions: Cytochorme P450 Drug Interaction Table. Indiana Universitiy School of Medicine (2007) http://medicine.iupui.edu/clinpharm/ddis/clinical-table/, Accessed [2014 Aug]
ReferenceNo conflict of interest.
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