Do intravenous fluid substitutions influence methotrexate clearance? An unanticipated impact of an intravenous sodium bicarbonate drug shortage.

BACKGROUND

National drug shortages of essential medications for childhood cancer have increasingly posed a challenge in the treatment of patients. The efficacy of standardized supportive care practices to avoid treatment-related toxicities may be limited during these drug shortages. High-dose methotrexate (HDMTX) plays a critical role in modern treatment protocols for acute lymphoblastic leukemia and requires stringent supportive care measures to mitigate toxicity. As the result of a national intravenous (IV) sodium bicarbonate shortage, institutional standard HDMTX supportive care guidelines had to be modified. We describe the unanticipated consequences on HDMTX clearance.

METHODS

We performed a retrospective chart review assessing the impact of alternative compositions of IV fluids on the mean 24-h methotrexate levels (Cp ) of 25 patients receiving 76 total HDMTX infusions at Texas Children's Hospital Cancer Center from March to October 2017. During the sodium bicarbonate drug shortage, all patients received IV hydration consisting of either dextrose 5%, 0.45% normal saline (D5 ½ NS-Group A) or dextrose 5%, 0.2% normal saline (D5 ¼ NS-Group B).

RESULTS

Patients receiving a higher total sodium dose demonstrated significantly lower Cp (25.36 ± 16.6 μMol) compared to patients receiving less sodium (53.9 ± 37.9 μMol; P < .001).

CONCLUSIONS

Our report shows that in the setting of IV sodium bicarbonate shortage, the composition of hydration IV fluids may affect methotrexate clearance. Patient who received a higher sodium load had a lower 24-h methotrexate level. This demonstrates the potential for unanticipated outcomes resulting from national drug shortages.