title: Potential drug interactions in cancer patients receiving supportive care exclusively.
abstract: Cancer patients at the end of life often take many medications and are at risk for drug interactions. The purpose of this study was to describe the epidemiology of potential drug interactions in cancer patients receiving supportive care exclusively. We retrospectively reviewed the charts of consecutive adult cancer outpatients attending palliative care clinics at the Princess Margaret Hospital, Toronto, Canada. Drugs were screened for interactions by the Drug Interaction Facts software, which classifies interactions by levels of severity (major, moderate, and minor) and scientific evidence (1-5, with 1=the strongest level of evidence). Among 372 eligible patients, 250 potential drug interactions were identified in 115 patients (31%, 95% confidence interval 26%-36%). The most common involved warfarin and phenytoin. Most interactions were classified as being of moderate severity (59%) and 42% of them were supported by Levels 1-3 of evidence. In multivariable analysis, increasing age (P<0.001), presence of comorbidity (P=0.001), cancer type (brain tumors, P<0.001), and increasing number of drugs (P<0.001) were associated with risk of drug interactions. Potential drug interactions are common in palliative care and mostly involve warfarin and anticonvulsants. Older patients, those with comorbid conditions, brain tumor patients, and those taking many medications are at greater risk of drug interactions.
authors.affiliation: Department of Medical Oncology and Hematology, Princess Margaret Hospital, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Rachel P
authors.initials: RP
authors.lastname: Riechelmann
authors.forename: Camilla
authors.initials: C
authors.lastname: Zimmermann
authors.forename: Sheray N
authors.initials: SN
authors.lastname: Chin
authors.forename: Lisa
authors.initials: L
authors.lastname: Wang
authors.forename: Aoife
authors.initials: A
authors.lastname: O'Carroll
authors.forename: Sanaz
authors.initials: S
authors.lastname: Zarinehbaf
authors.forename: Monika K
authors.initials: MK
authors.lastname: Krzyzanowska
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000009:adverse effects; D000927:Anticonvulsants / Q000009:adverse effects; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D004347:Drug Interactions; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000150:complications* / Q000628:therapy*; D010166:Palliative Care; D012189:Retrospective Studies; D014859:Warfarin / Q000009:adverse effects
chemical_list: D000925:Anticoagulants; D000927:Anticonvulsants; D014859:Warfarin