SLC18A2 and thanatophoric dysplasia: Although TBZ is the first VMAT2 inhibitor, initially used as an agent to ameliorate symptoms of TD, and DTBZ retains the VMAT2 affinities of the non-deuterated isomers, TBZ/DTBZ is a racemate of two ketone enantiomers, and its metabolism is complex, illustrated in Figure 1A.