⚡ Quick answer: Mirtazapine dosage calculator for dogs. 0.5-1 mg/kg PO every 24-48 hours. Appetite stimulant + antiemetic for CKD inappetence, cancer cachexia, chronic illness. Serotonin syndrome warning.
Mirtazapine for Dogs – Appetite Stimulant + Antiemetic
Mirtazapine is a tetracyclic antidepressant used primarily for appetite stimulation + antiemetic effects in dogs.
Dose
0.5-1.0 mg/kg PO every 24 hours
CKD or hepatic disease: every 48 hours
Dose Reference Table
| Weight | Dose Range |
|---|---|
| 5 kg | 2.5-5 mg |
| 10 kg | 5-10 mg |
| 15 kg | 7.5-15 mg |
| 20 kg | 10-20 mg |
| 30 kg | 15-30 mg |
| 40 kg | 20-40 mg |
Tablet sizes: 7.5, 15, 30, 45 mg (splittable).
Mechanism
- Alpha-2 adrenergic antagonist (increases NE + serotonin)
- 5-HT2/5-HT3 antagonist (antiemetic)
- H1 antihistamine (sedation)
Indications
- CKD inappetence (most common)
- Cancer cachexia
- Post-op anorexia
- Chronic illness with weight loss
- Antiemetic adjunct (Cerenia primary)
- Anxiety adjunct
Onset
1-2 days for appetite stimulation. Rapid effect.
⚠ Serotonin Syndrome Risk
CONTRAINDICATED
- MAOIs (selegiline/Anipryl)
Use Cautiously
- SSRIs (fluoxetine, sertraline)
- Tramadol
- Trazodone
- Other antidepressants
Side Effects
- Sedation (common; usually mild, can be helpful)
- Hyperactivity (paradoxical, rare)
- Mild GI upset (uncommon)
- Vocalization (more in cats)
Mirataz Transdermal
Cat-labeled (1.5% transdermal gel) – off-label dog use limited. Oral tablets standard for dogs.
Frequently Asked Questions
How much mirtazapine should I give my dog?
STANDARD DOSE: 0.5-1.0 mg/kg PO every 24 hours
CKD or hepatic disease: every 48 hours
EXAMPLES:
- 5 kg = 2.5-5 mg daily
- 10 kg = 5-10 mg
- 15 kg = 7.5-15 mg
- 20 kg = 10-20 mg
- 30 kg = 15-30 mg
- 40 kg = 20-40 mg. TABLETS 7.5, 15, 30, 45 mg (splittable). Start at LOW end – increase if needed. Many dogs respond at 0.5 mg/kg. ONSET 1-2 days. Give with or without food. Mirataz transdermal CAT-LABELED only – off-label dog use limited; oral standard for dogs
What is mirtazapine used for in dogs?
Primary uses: 1) APPETITE STIMULATION (most common) – CKD inappetence, cancer cachexia, chronic illness, post-op anorexia, hospice care; 2) ANTIEMETIC adjunct (Cerenia is primary anti-nausea); 3) Anxiety adjunct in some dogs; 4) Cachexia management; 5) Hospice quality of life. MECHANISM: alpha-2 adrenergic antagonist increases norepinephrine + serotonin; 5-HT2/5-HT3 antagonist (antiemetic); H1 antihistamine (sedation + appetite). EFFECTIVE for CKD-related anorexia (very common indication). Often combined with maropitant (Cerenia) for nausea + Denamarin/probiotics for chronic disease. Side effects mild – sedation most common (can be helpful). Discuss with vet for specific indication.
Can I give mirtazapine with trazodone or Prozac?
CAUTION – serotonin syndrome risk. SEROTONIN SYNDROME signs: hyperthermia, tremor, hyperreflexia, agitation, tachycardia, hypertension, dilated pupils, seizures. MAOIs (selegiline/Anipryl) ABSOLUTELY CONTRAINDICATED – severe risk. SSRIs (fluoxetine/Reconcile, sertraline, paroxetine), SNRIs, TRAMADOL, TRAZODONE – use with caution; monitor closely. If combination needed
- Use LOWEST effective doses
- Watch for serotonin syndrome signs
- Cyproheptadine 1.1 mg/kg PO is antidote if syndrome develops
- Veterinary supervision
- Don’t add multiple serotonergic drugs simultaneously
SAFER pain alternatives in dogs on mirtazapine: gabapentin (no serotonergic effect), Librela (anti-NGF), Adequan. Discuss any new medications with vet
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References & Further Reading
The dosing ranges and safety information on this page are drawn from the following veterinary references. Always defer to your own veterinarian and the manufacturer’s label for your specific product.
- Plumb DC. Mirtazapine.
- Quimby JM et al. Mirtazapine in cats with CKD (extrapolated).
- Giorgi M et al. Pharmacokinetics of mirtazapine in dogs.
- Mirataz product information – Kindred Biosciences (cat label).
- PuppaDogs. Entyce Calculator, Cerenia Calculator. puppadogs.com.
⚕️ Medical disclaimer
The information on this page is intended for educational purposes only and does not replace a hands-on veterinary examination. Drug doses depend on your dog’s complete clinical picture, concurrent medications, and the exact product formulation. Always confirm dosing with your veterinarian before administering any medication, and contact a 24-hour veterinary emergency service or animal poison control immediately if you suspect a medication overdose or adverse reaction. PuppaDogs editorial standards: every drug dose published here is cross-checked against multiple authoritative veterinary references and reviewed by the PuppaDogs Veterinary Editorial Team before publication.
