Abstract
Background: High dose methotrexate (MTX) is an important agent in the prevention and treatment of cancer in the central nervous system. Administration of this drug requires alkalization of the urine, which traditionally includes the use of intravenous (IV) sodium bicarbonate (bicarb). In May 2017, IV bicarb was on national shortage; at the University of Virginia, pharmacists and physicians designed an oral (PO) regimen using bicarb and acetazolamide to ensure patients could continue receiving MTX. As there are limited published data, we aimed to assess the safety and the impact on time to start of MTX.
Methods: Retrospective chart review was done 5/2016-4/2017 to establish a baseline time to methotrexate. In a prospective analysis, data was collected from May 2017 to May 2018 on all patients who received MTX. For patients receiving the PO regimen, bicarb 2,600 mg PO 6 times daily and acetazolamide 250 mg PO every 6 hours were the initial doses and titrated to maintain a urine pH greater than or equal to 7. The primary endpoint was time to MTX for patients with planned admissions who start MTX upon meeting urine pH and output parameters. Secondary endpoints included incidence of acute kidney injury (AKI) and delayed methotrexate clearance for all patient encounters. AKI was defined using Kidney Disease Improving Global Outcomes criteria. Delayed MTX clearance was defined based on failure to meet goal levels based on published chemotherapy protocols. χ2 analysis was completed on categorical variables. A statistical process control chart (p-chart) depicted time to MTX.
Results: A total of 162 patient encounters were included in the analysis. The median age of patients receiving oral bicarb was 51 years (range 21-69) and was 51 years (range 21-63) for patients receiving IV bicarb. Eighty-six encounters were planned admissions that started MTX when urine parameters were met and received either IV (n=32) or PO bicarb (n=54). In these patients median time from admission to MTX was 8.4 vs 7.9 hours, respectively. Figure 1 shows consecutive patients receiving MTX prior to, during, and after resolution of the IV bicarb shortage; there is less variability and fewer outliers in the MTX start time when exclusively administering the PO regimen during the shortage. For the secondary analysis an additional 76 encounters with either unplanned admissions or predetermined MTX start time on subsequent day to admission were analyzed for safety outcomes. The rate of AKI was 14.5% vs 8.9% in the PO vs IV groups, respectively (p=0.28). There was no difference in incidence of delayed methotrexate clearance with 26.5% of patients in PO group vs 25.3% patients in IV group (p=0.87). Length of stay was slightly increased in patients who received PO vs IV alkalization (3.78 vs 3.15 days).
Conclusion: Our alternative oral bicarb and acetazolamide urine alkalization regimen appears safe in patients receiving MTX and allowed for continued treatment of patients during a national IV bicarb shortage. Time to start of MTX was decreased with implementation of PO regimen, and there appeared to be a more predictable start time for MTX. While not significant, the higher incidence of AKI in PO group warrants further analysis. Future efforts include using oral outpatient alkalization prior to inpatient admission to work towards improving length of stay.
No relevant conflicts of interest to declare.
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