Capecitabine and Warfarin Interaction: A Case Report With Review of Literature and Management Options

Capecitabine is an orally active prodrug of 5-fluorouracil with improved safety and efficacy that is extensively used as an antineoplastic agent. It is converted to 5-Fluorouracil in the liver and tumor tissues. In vitro assays did not reveal any significant potential for interaction between capecitabine and its metabolites with warfarin. However, several reports provided clinical evidence of such interaction resulting in an elevated international normalized ratio (INR) and bleeding. Here, we report another case of capecitabine and warfarin concurrent administration that resulted in sub- or supra- therapeutic INR without any bleeding episode or venous-thromboembolic event through the follow-up period. Moreover, a review of available management options is also presented in this paper.

Effect of Switching from the Initial Direct Oral Anticoagulant to Another One on Exacerbation of Venous Thromboembolism in Patients with Cancer: A Retrospective Study

Objective: To determine the effect of switching from the initial direct oral anticoagulant (DOAC) to another DOAC on exacerbation of deep vein thrombosis (DVT).

Materials and Methods: We retrospectively reviewed the data of patients with advanced cancer who experienced exacerbated DVT during initial treatment with DOAC due to new venous thromboembolism (VTE). After switching to another DOAC for VTE recurrence, changes in the thrombus and bleeding were evaluated for 3 months. Eighteen patients met these criteria. We compared the effect of anticoagulant switching on the switched-drug group in those 18 patients with the effect of no anticoagulant switching on the single-drug group of patients (n=78) with a similar background.

Results: The recurrence rate of VTE in the switched-drug group was 6%. Non-major bleeding occurred in 11% of patients. Recurrent VTE occurred in 6% of patients in both the switched-drug and single-drug groups, respectively [risk ratio (RR): 0.9, 95% confidence interval (CI): 0.11–7.6]. Non-major bleeding occurred in 11% and 14% of patients in the switched-drug and single-drug groups, respectively (RR: 0.79, 95%CI: 0.19–3.2).

Conclusion: Switching DOAC may be a treatment option for exacerbation of DVT in patients with advanced cancer.

Impact of capecitabine and S-1 on anticoagulant activity of warfarin in patients with gastrointestinal cancer

PURPOSE

Capecitabine and S-1 are orally administered fluoropyrimidine anticancer drugs widely used to treat gastrointestinal cancer. While anticoagulant therapy for cancer patients is recommended, many studies have shown that the effects of warfarin are enhanced by its interaction with fluoropyrimidine. We investigated the effects of capecitabine or S-1 on the anticoagulant activity of warfarin in patients coadministered both drugs.

METHODS

We retrospectively investigated the clinical features of and anticoagulant activity in nine consecutive patients who received capecitabine or S-1 in combination with warfarin from January 2008 to December 2014 at our institution. The prothrombin time international normalized ratio divided by current warfarin dosage (PT-INR/dose) was measured over time to evaluate warfarin titer in each patient.

RESULTS

Reductions in warfarin dosage were required, from 2.6 mg/day before chemotherapy to a minimum of 1.7 mg/day after chemotherapy initiation, on average. The median time until the first dosage reduction after initiation was 22 days for the capecitabine group and 43 days for the S-1 group. The median time until minimal dosage of warfarin was reached was 43 days in both groups. PT-INR/dose was elevated from 0.85 before chemotherapy to a maximum of 1.41 after its initiation. The median time until the maximal PT-INR/dose was reached was 46 days for the capecitabine group and 46.5 days for the S-1 group.

CONCLUSIONS

The anticoagulant activity of warfarin may be enhanced by coadministration with capecitabine or S-1. Close monitoring of anticoagulant activity is required to avoid a hyperfibrinolytic state due to a severe adverse interaction.

Cardiovascular Toxicity and Management of Targeted Cancer Therapy

The advent of effective oral, molecular-targeted drugs in oncology has changed many incurable malignancies such as chronic myeloid leukemia into chronic diseases similar to coronary artery disease and diabetes mellitus. Oral agents including monoclonal antibodies, kinase inhibitors and hormone receptor blockers offer patients with cancer incremental improvements in both overall survival and quality of life. As it is imperative to recognize and manage side effects of platelet inhibitors, beta blockers, statins, human immunodeficiency virus drugs and fluoroquinolones by all healthcare providers, the same holds true for these newer targeted therapies; patients may present to their generalist or other subspecialist with drug-related symptoms. Cardiovascular adverse events are among the most frequent, and potentially serious, health issues in outpatient clinics, and among the most frequent side effects of targeted chemotherapy. Data support improved patient outcomes and satisfaction when primary care and other providers are cognizant of chemotherapy side effects, allowing for earlier intervention and reduction in morbidity and healthcare costs. With the implementation of accountable care and pay for performance, improved communication between generalists and subspecialists is essential to deliver cost-effective patient care.

Prevalence of potential drug-drug interactions in cancer patients treated with oral anticancer drugs

BACKGROUND

Potential drug-drug interactions (PDDIs) in patients with cancer are common, but have not previously been quantified for oral anticancer treatment. We assessed the prevalence and seriousness of potential PDDIs among ambulatory cancer patients on oral anticancer treatment.

METHODS

A search was conducted in a computer-based medication prescription system for dispensing oral anticancer drugs to outpatients in three Dutch centres. Potential drug-drug interactions were identified using electronic (Drug Interaction Fact software) and manual screening methods (peer-reviewed reports).

RESULTS

In the 898 patients included in the study, 1359 PDDIs were identified in 426 patients (46%, 95% confidence interval (CI)=42-50%). In 143 patients (16%), a major PDDI was identified. The drug classes most frequently involved in a major PDDI were coumarins and opioids. The majority of cases concerned central nervous system interactions, PDDIs that can cause gastrointestinal toxicity and prolongation of QT intervals. In multivariate analysis, concomitant use of more drugs (odds ratio (OR)=1.66, 95% CI=1.54-1.78, P<0001) and genito-urinary cancer (OR=0.25, 95% CI=0.12-0.52, P<0001) were risk factors.

CONCLUSION

Potential drug-drug interactions are very common among cancer patients on oral cancer therapy. Physicians and pharmacists should be more aware of these potential interactions.