Doxepin

Doxepin: Uses, Dosage and Side Effects

Overview

• Doxepin inhibits the reuptake of noradrenaline and serotonin in the brain, resulting in antidepressant activity, while the inhibition of H1 and H2 receptors produces antipruritic effects.
• Desmethyldoxepin, its metabolite, is also psychoactive.

Uses of Doxepin

• Management of pruritus and psychogenic dermatoses where there is a component of anxiety, including canine acral lick dermatitis and compulsive disorders.

Dose of Doxepin in Dogs and Cats

Dogs:

3–5 mg/kg p.o. q8–12h, maximum dose 150 mg q12h.

Cats:

0.5–1.0 mg/kg p.o. q12–24h

Side Effects of Doxepin in Dogs and Cats

• In humans, there have been reports of sedation, parched mouth, diarrhoea, vomiting, excitability, arrhythmias, hypotension, syncope, increased appetite, weight gain, and, less frequently, seizures and bone marrow disorders.

Contraindications of Doxepin in Dogs and Cats

• Hypersensitivity to tricyclic antidepressants, glaucoma, history of seizure or urinary retention and severe liver disease.

Some Notes:

• It should not be used with monoamine oxidase inhibitors or drugs metabolized by cytochrome P450 2D6, e.g. chlorphenamine and cimetidine.
• It should not generally be used alongside other serotonergic agents given the risk of serotonin syndrome, although use alongside trazodone may be considered in exceptional cases, so long as the patient is carefully monitored for signs of serotonin syndrome.