What is mirtazapine and it's dose rate in dog and cat from plums book and other different books
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The library does not contain veterinary textbooks (Plumb's or others). The available library is focused on human medicine. Let me provide a comprehensive answer from my knowledge about mirtazapine in dogs and cats, drawing on Plumb's Veterinary Drug Handbook and other veterinary references.
Mirtazapine in Dogs and Cats
What is Mirtazapine?
Mirtazapine is a noradrenergic and specific serotonergic antidepressant (NaSSA). In veterinary medicine, it is used primarily as an appetite stimulant and antiemetic, not as an antidepressant.
Mechanism of Action:
- Blocks central α₂-adrenergic autoreceptors and heteroreceptors → increases norepinephrine and serotonin release
- Potently antagonizes 5-HT₂ and 5-HT₃ receptors → antiemetic and appetite-stimulating effects
- Blocks H₁ histamine receptors → sedation
- Blocks 5-HT₃ receptors in the chemoreceptor trigger zone (CRTZ) → antiemetic effect
Key Clinical Uses in Veterinary Medicine:
- Appetite stimulation (especially in cats with hepatic lipidosis, CKD, cancer cachexia)
- Nausea/vomiting management
- Weight maintenance in chronic disease
Dose Rates
📘 Plumb's Veterinary Drug Handbook (8th–9th Edition)
| Species | Indication | Dose | Route | Frequency |
|---|---|---|---|---|
| Cats | Appetite stimulation | 1.875 mg (¼ of a 7.5 mg tablet) | PO | Every 72 hours (q72h) |
| Cats | Appetite stimulation (transdermal) | 2 mg | Transdermal (ear pinna) | Every 72 hours (q72h) |
| Dogs | Appetite stimulation | 1.88–3.75 mg (small dogs) up to 3.75–30 mg (larger dogs) | PO | Every 24–72 hours |
Note (Plumb's): In cats, the q72h dosing interval is critical because mirtazapine has a longer half-life in cats (~40 hours) compared to dogs (~7–11 hours) and humans. More frequent dosing risks serotonin syndrome.
📗 Transdermal Mirtazapine (Mirataz® — FDA-approved for cats)
An FDA-approved transdermal ointment (Mirataz, 2% mirtazapine) is available specifically for cats:
- Dose: 2 mg (equivalent to a ribbon of ~1.5 cm of ointment) applied to the inner pinna
- Frequency: Every 24 hours for 14 days
- Indication: Management of weight loss in cats
📙 Veterinary Drug Handbook / Small Animal Internal Medicine References
Cats:
| Source | Dose | Frequency |
|---|---|---|
| Plumb's | 1.875 mg PO | q72h |
| Plumb's (transdermal) | 2 mg | q72h |
| Mirataz (FDA label) | 2 mg transdermal | q24h |
| BSAVA Small Animal Formulary | 1.875 mg PO | q72h |
Dogs:
| Source | Dose | Frequency |
|---|---|---|
| Plumb's | 1.88–30 mg PO (weight-based) | q24h |
| Small Animal Clinical Pharmacology (Maddison) | 0.6 mg/kg PO | q24h |
| Tilley & Smith (5-Minute Vet Consult) | 3.75–30 mg PO (per dog) | q24h–q48h |
Important Pharmacokinetic Differences: Dog vs. Cat
| Parameter | Dog | Cat |
|---|---|---|
| Half-life | ~7–11 hours | ~40 hours |
| Dosing interval | q24h | q72h |
| Metabolism | Hepatic (CYP) | Slower hepatic |
| Renal excretion | Yes | Yes — reduce dose in CKD |
Adverse Effects / Warnings
- Cats: Vocalization, hyperexcitability, tremors, hypersalivation — signs of serotonin syndrome (especially with concurrent serotonergic drugs like cyproheptadine antagonism, MAOIs, tramadol, SSRIs)
- Dogs: Sedation, ataxia, tachycardia
- Both species: Do NOT combine with MAO inhibitors (selegiline) — risk of serotonin syndrome
- Reduce dose in hepatic or renal disease
- Cyproheptadine can be used as an antidote in cases of mirtazapine toxicity
Key Points Summary
- Cats: 1.875 mg PO q72h OR 2 mg transdermal q72h (or q24h per Mirataz label)
- Dogs: ~1.88–30 mg PO q24h depending on body weight (~0.6 mg/kg)
- Primary use in both species: appetite stimulation and antiemesis, not antidepression
- Cats have a much longer half-life — never dose more frequently than every 48–72 hours orally to avoid toxicity
Note: The medical library available here does not contain Plumb's Veterinary Drug Handbook or other veterinary-specific textbooks. The dosing information above is drawn from established veterinary pharmacology references including Plumb's (8th/9th ed.), the Mirataz® FDA label, BSAVA Small Animal Formulary, and Tilley & Smith's 5-Minute Veterinary Consult. Always confirm current doses with the latest edition of Plumb's or your formulary.
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