DL-TBOA ammonium is a potent, non-transportable inhibitor of excitatory amino acid transporters. Its inhibitory effects are demonstrated by IC50 values of 70 μM, 6 μM, and 6 μM for excitatory amino acid transporter-1 (EAAT1), EAAT2, and EAAT3, respectively. Additionally, DL-TBOA ammonium significantly hampers the uptake of [14C]glutamate in COS-1 cell lines expressing human EAAT1 and EAAT2, evident by Ki values of 42 μM and 5.7 μM, respectively. Furthermore, this compound competitively blocks EAAT4 and EAAT5, with Ki values of 4.4 μM and 3.2 μM, respectively.