Cetirizine 1-[(4-Chlorophenyl)phenylmethyl]piperazine Amide-d8 is labelled Cetirizine 1-[(4-Chlorophenyl)phenylmethyl]piperazine Amide (C281155) which is a possible impurity of Cetirizine (C281100), a nonsedating type histamine H1-receptor antagonist. Cetirizine is a major metabolite of Hydroxyzine.