2-(2-(4-(Dibenzo[b,f][1,4]thiazepin-11-yl)piperazin-1-yl-d8)ethoxy)ethyl Acetate is the labeled analogue of 2-(2-(4-(Dibenzo[b,f][1,4]thiazepin-11-yl)piperazin-1-yl)ethoxy)ethyl Acetate (D417095), an impurity of Quetiapine Hemifumarate (Q510000), an antipsychotic.