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PS-099 Drug-drug interactions in fluoropyrimidines-based regimens used in colorectal cancer treatment
  1. P Cavaco1,
  2. AS Santos1,
  3. C Cortés2,
  4. C Lopes1,
  5. B Madureira1,
  6. E Viegas1,
  7. F Falcão1
  1. 1S. Francisco Xavier Hospital, Pharmacy, Lisbon, Portugal
  2. 2Valencia University, Valencia University, Valencia, Portugal


Background Drug interactions in oncology are of particular importance due to the narrow therapeutic range and inherent toxicity. The incidence of interactions increases when patients are polymedicated, which is very common in cancer patients as they often have other co-morbidities.

Purpose To identify potential drug–drug interactions in patients with colorectal cancer treated with fluoropyrimidines-based regimens and concomitant treatment.

Material and methods Retrospective study to evaluate drug interactions in patients with colorectal cancer who started chemotherapy between January and March 2014, in a central hospital, and who were also prescribed other drugs. Interactions were screened using the Lexi-Interact database between chemotherapy regimens including FOLFOX4, mFOLFOX6, FOLFIRI, capecitabine and fluorouracil continuous infusion, supportive treatment for prevention of emesis (dexamethasone, ondansetron) and other prescribed treatment.

Results Of the patients who started fluoropyrimidines-based chemotherapy, 29 were also prescribed other drugs, the majority cardiovascular and Central Nervous System drugs. Of the 108 drugs prescribed, 20 interacted with the chemotherapeutic regimen, and accounted for 34 interactions, with an average of 1.2 interactions per prescription. According to the Lexi-Interact database 10 had risk rating C and required monitoring of side effects; 23 had risk rating D and were recommended for treatment modification or aggressive monitoring; 1 had risk rating X which required avoidance of the combination. The drugs included in the chemotherapy regimens with the highest number of interactions were dexamethasone (n = 20) and fluorouracil (n = 8).

Conclusion The screening of drugs for the treatment of co-morbidities was based on electronic medical records hence OTC drugs and dietary supplements were not included in this study. The identification of these drug interactions enables their inclusion in the prescription program, allowing alerts to be issued at the time of prescription.


  1. Crul M, Yap KD, Terpstra WE. Frequent interactions between chemotherapy and community-dispensed drugs in a continuous screening programme. Eur J Hosp Pharm 2012;19:171

ReferenceNo conflict of interest.

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