[{"from": "human", "value": "Could you give me a brief overview of this molecule? [C][C][N][Branch1][#C][C][C][N][Ring1][=Branch1][C][C][O][C][C][=Branch1][C][=O][O][C@H1][Branch1][=Branch2][C][=C][C][=C][C][=C][Ring1][=Branch1][C][=C][C][=C][Branch1][Branch1][C][=C][Ring1][=Branch1][Cl]"}, {"from": "gpt", "value": "The molecule is a selective histamine H1 antagonist used to treat a variety of allergic symptoms. It is the R enantiomer of [cetirizine]. Levocetirizine has greater affinity for the histamine H1 receptor than cetirizine.  Levocetirizine was granted FDA approval in 1995."}]