Intravenous (IV) sodium bicarbonate is typically used in alkalization regimens for the safe use of the chemotherapeutic agent high-dose methotrexate (HDMTX). Urine parameters including urine output and pH are important in order to minimize the risk of kidney injury, which increases adverse effects and hospital length of stay following HDMTX. IV sodium bicarbonate has been on shortage, and there are limited literature describing the safety of alternative regimens.A single institution, prospective analysis of non-Hodgkin's lymphoma and acute lymphoblastic leukemia patients receiving HDMTX for central nervous system (CNS) prophylaxis or disease. Patients received an oral (PO) regimen of sodium bicarbonate and acetazolamide to achieve a urine pH >7. This cohort was compared to a subsequent IV sodium bicarbonate control cohort. Multiple co-primary safety outcomes assessed the incidences of acute kidney injury and delayed methotrexate clearance as well as change in liver function tests. Secondary outcomes included time to urine pH, time to urine output, and length of stay.A total of 126 encounters were studied for the primary safety outcome. There was no difference between AKI incidence in patients receiving the PO alkalization regimen compared to patients receiving IV sodium bicarbonate (14.5% vs 9.3%, respectively, P=0.41). There was no difference in methotrexate clearance between the PO and IV groups (26.5% vs 37.2%, respectively, P=0.21). The use of PO alkalization regimen is estimated to have saved 2002 vials of IV sodium bicarbonate and was approximately US$226 less expensive per encounter.This analysis supports the use of PO regimens to achieve urine alkalization necessary for safe administration of HDMTX during periods of IV sodium bicarbonate shortage. Further studies may determine optimal dosing strategies that decrease length of stay and ensure noninferiority of efficacy outcomes with PO regimens for urine alkalization with HDMTX.