Doxepin HCl

What is this medication for?

• Adjunct therapy of psychogenic dermatoses (acral lick, tail-chasing alopecia — with anxiety component); itching with behavioral driver
• Antihistamine efficacy for atopic dermatitis is questionable

How is it given?

Give exactly as your veterinarian prescribed — never change the dose or stop on your own unless your veterinarian has told you to.

What if I miss a dose?

• Give it as soon as you remember — unless it is almost time for the next dose (then skip the missed one; never double up).
• Call your clinic if you miss more than one dose in a row.

Side effects — what should I watch for?

Effects listed as common in this handout

• Hyperexcitability, stomach/intestinal distress, low energy/tiredness (Most likely)

Worth a phone call to your veterinarian

• Ventricular arrhythmias (Overdose — TCA cardiotoxicity)

⚠️ Contact your veterinarian or an emergency clinic IMMEDIATELY if you notice

• Urinary retention, glaucoma exacerbation (Anticholinergic)

Before starting (or refilling), tell your veterinarian if your pet:

• has or has had: TCA sensitivity; MAOIs (selegiline?); urinary retention or glaucoma (probably)
• has or has had: Seizure disorders, cardiac disease, hyperthyroidism (TCA cautions)

• is pregnant, nursing, or used for breeding
• is taking any other medications, supplements, or flea/tick products, including:
  • MAOIs
  • Anticholinergics, antihistamines
  • Antiarrhythmics/QT-prolongers

Storage and handling

Room temperature; bitter liquid — capsule administration preferred.

Good to know

• The itchy-anxious patient's two-in-one: doxepin treats the anxiety-driven lick cycle AND carries H1 blockade — rationale for psychogenic dermatoses where hydroxyzine alone fails.
• TCA overdose = arrhythmia emergency (sodium bicarbonate is the human antidote approach).
• Perrin note: urine retention is the TCA class adverse to watch (shared with amitriptyline/clomipramine).