Final answer:
Amitriptyline, a tricyclic antidepressant, can be used as an antipruritic agent and in treating gastric ulcers due to its histamine-blocking properties.
Step-by-step explanation:
The antidepressant that can be used as an antipruritic agent and for the treatment of gastric ulcer due to its potent histamine blockade is D. Amitriptyline. Amitriptyline is one of the tricyclic antidepressants, noted for its antihistaminic properties among its numerous pharmacological actions. Unlike selective serotonin reuptake inhibitors (SSRIs) like fluoxetine (Prozac), which are more specific in their action on serotonin reuptake, tricyclic antidepressants also have significant anticholinergic effects which include histamine H1 receptor blockade. This property makes amitriptyline useful not just in the treatment of depression, but also in the management of pruritus (itching) and as an adjunct treatment for peptic ulcers.