Doxepin (DXP)

Doxepin is used to treat depression, anxiety disorders, pruritus, insomnia and as a second line treatment of chronic idiopathic urticaria (hives). It should not be used within fourteen days of using a monoamine oxidase inhibitor such as phenelzine due to the potential for serotonin syndrome to develop. Its use in those on CYP2D6 inhibitors such as fluoxetine or quinidine is recommended against due to the potential for its accumulation in the absence of full CYP2D6 catalytic activity. Hepatic enzyme inducers such as carbamazepine, phenytoin and barbiturates are advised against in patients receiving TCAs like doxepin due to the potential for problematically rapid metabolism of doxepin to occur in these individuals. Sympathomimietic agents may have their effects potentiated by TCAs like doxepin. Doxepin also may potentiate the adverse effects of anticholinergic agents such as benztropine, atropine and hyoscine (scopolamine).