Final answer:
Doxepin is the tricyclic antidepressant with the most significant antihistaminic activity among the options provided.
Step-by-step explanation:
Of the tricyclic antidepressants listed, Doxepin has the most antihistaminic activity. Tricyclic antidepressants (TCAs) like imipramine and amitriptyline are widely used for the treatment of major depression. These compounds share a similar structure but exhibit different pharmacological profiles. Tertiary amine TCAs typically have stronger antihistaminic effects due to their higher affinity for histamine receptors.
Doxepin is known for its strong antihistaminic properties and is sometimes even used in lower doses to treat issues like chronic itch. This distinguishes it from other TCAs like Amoxapine, Clomipramine, Desipramine, and Nortriptyline which have varying degrees of antihistaminic activity but are not as potent in that regard as Doxepin is.