Used primarily as an intermediate in the synthesis of tricyclic antidepressant drugs, particularly in the production of doxepin. It plays a key role in pharmaceutical manufacturing due to its structural similarity to bioactive tricyclic compounds that modulate neurotransmitter activity in the central nervous system. Its quaternary ammonium structure enhances solubility and stability during drug formulation processes. Also utilized in research settings for developing analogs with improved pharmacological profiles.