# Cyproheptadine: veterinary dose and monograph

> Cyproheptadine is a veterinary drug. An antihistamine (H1 blocker) with notable ANTISEROTONERGIC and antimuscarinic activity, giving it several distinct veterinary uses: an APPETITE STIMULANT in cats (its best-known use), an adjunct bronchodilator/anti-inflammatory in feline… Indications include appetite stimulation in inappetent cats; serotonin syndrome — antidote (serotonin antagonist); feline asthma / bronchoconstriction (adjunct, antiserotonergic bronchodilation). This monograph lists 5 reference doses for dogs, cats and horses, each with route, frequency and source.

Source: https://vetmasterji.com/drugs/cyproheptadine · Last reviewed: 2026-10-01

## At a glance

- **Drug class:** Veterinary drug
- **Also known as:** Periactin, Practin, Ciplactin
- **Species with doses:** Dogs, Cats and Horses
- **Routes:** PO
- **Last reviewed:** 1 October 2026

## Indications

- Appetite stimulation in inappetent cats
- Serotonin syndrome — antidote (serotonin antagonist)
- Feline asthma / bronchoconstriction (adjunct, antiserotonergic bronchodilation)
- Equine PPID / headshaking (historical/adjunct uses)

## Cyproheptadine dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

### Dogs

*Cyproheptadine doses for dogs*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Serotonin syndrome (antidote) | 1.1 mg/kg | PO | q4–6h until signs resolve | — |

- Serotonin syndrome (antidote): Plumb’s p.334 (Wismer 2006): 1.1 mg/kg PO, repeated q4–6h as needed; crush in saline and give per rectum if vomiting. Appetite stimulation: 0.2 mg/kg PO q12h (Moore 2005); antihistamine 0.3–2 mg/kg twice daily (Papich 5e: 0.5–1.1 mg/kg q8–12h).

### Cats

*Cyproheptadine doses for cats*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Appetite stimulation | 1–4 mg/cat | PO | q12–24h | — |
| Serotonin syndrome (antidote) | 2–4 mg/cat | PO | q4–6h until signs resolve | — |
| Antihistamine / asthma adjunct | 1–2 mg/cat | PO | q12h | — |

- Appetite stimulation: Papich 5e: 2 mg per cat PO. Plumb’s p.334: 2–4 mg per cat once or twice daily (Davenport; Ogilvie); 2 mg per cat q12h (Smith); 0.35–1 mg/kg q12h (Moore); renal insufficiency 1 mg per cat q12h (Scherk). Stop if it causes excitement.
- Serotonin syndrome (antidote): Plumb’s p.334 (Wismer 2006): cats 2–4 mg total PO, repeated q4–6h as needed; if vomiting, crush tablets in saline and give rectally.
- Antihistamine / asthma adjunct: Papich 5e: feline asthma 1–2 mg per cat q12h; antihistamine 2–4 mg per cat q12–24h or 0.5–1.1 mg/kg q8–12h; inappropriate urination 2 mg q12h then 1 mg q12h. Plumb’s p.334: pruritus 2 mg per cat or 1.1 mg/kg q12h; asthma 2 mg q12h — response in 4–7 days (Padrid).

### Horses

*Cyproheptadine doses for horses*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Headshaking / PPID (adjunct, historical) | 0.25–0.6 mg/kg | PO | q12h | — |

- Headshaking / PPID (adjunct, historical): Papich 5e: 0.5 mg/kg q12h PO; headshaking 0.3 mg/kg q12h. Plumb’s p.334: photic headshaking 0.3–0.6 mg/kg PO q12h; Cushing’s 0.25 mg/kg once daily for 4–8 weeks then twice daily if needed — only about ⅓ respond, pergolide is the drug of choice (Toribio; Young). ARCI Class 4.

## Contraindications

Glaucoma, urinary retention, GI obstruction (anticholinergic). Significant hepatic impairment. Pregnancy (limited data). Concurrent need for serotonergic drug effect (it will antagonise SSRIs/behavioural serotonergics). Known hypersensitivity.

## Species-specific warnings

> **Caution:** Cats: Paradoxical excitement/aggression can occur — discontinue if seen. Anticholinergic effects may cause urinary retention; use cautiously in lower-urinary-tract patients.

## Adverse effects

- Sedation, lethargy
- Anticholinergic effects (dry mouth, urinary retention, constipation)
- Paradoxical excitement/aggression in some cats
- Increased appetite/weight gain (often the desired effect)

## Drug interactions

- SSRIs / serotonergic behavioural drugs (fluoxetine, clomipramine): cyproheptadine ANTAGONISES their intended effect — avoid combining for behaviour (but this antagonism is exactly why it treats serotonin syndrome)
- CNS depressants: additive sedation
- Anticholinergics: additive (urinary retention, ileus)

## Pregnancy and lactation

Limited data; avoid in pregnancy unless clearly needed.

## Monitoring

- Appetite/food intake response (cats) within 1–2 days
- Sedation, excitement, anticholinergic effects (urination)
- For serotonin syndrome: resolution of agitation/tremor/hyperthermia
- Do not co-use with serotonergic behavioural drugs

## Toxicity and overdose

Overdose causes pronounced sedation or paradoxical CNS excitation, anticholinergic signs (mydriasis, tachycardia, urinary retention, ileus), and at high doses tremor/seizures. Generally a wide margin at appetite-stimulant doses.

Management: No specific antidote. Supportive — manage sedation/excitation and anticholinergic complications (bladder, ileus); benzodiazepines for agitation/seizures; fluids. Decontaminate large recent ingestions.

## Clinical pearls

- A go-to feline appetite stimulant (per-cat dosing) — works via central serotonin (5-HT2) blockade; stop it if it causes excitement instead
- It is the ANTIDOTE for serotonin syndrome (e.g. SSRI/tramadol overdose) — keep it in mind for serotonergic toxicoses
- Because it blocks serotonin, do NOT combine it with SSRIs/serotonergic behaviour drugs you want to work
- Mirtazapine (especially transdermal) has become a popular alternative appetite stimulant in cats

## Mechanism of action

Blocks H1 histamine receptors (antihistamine/antipruritic, sedating) and, importantly, serotonin (5-HT2) receptors — the antiserotonergic action underlies both its appetite-stimulant effect (central 5-HT2 blockade increases food intake) and its role as the antidote for serotonin syndrome (it antagonises the excess serotonergic signalling). It also has antimuscarinic (anticholinergic) activity.

## Formulations and products

- 4 mg tablet
- Syrup 0.5 mg/mL (2 mg/5 mL)
- Practin — 4 mg tablet; 2 mg/5 mL syrup, Tablet / syrup (human-label)
- Ciplactin — 4 mg tablet; syrup, Tablet / syrup (human-label)

## Storage

Tablets/syrup: 15–30 °C, dry, protect from light.

## Before you use this dose

> **Caution:** Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

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## Frequently asked questions

### What is the dose of Cyproheptadine for dogs?

Reference doses for Cyproheptadine in dogs: 1.1 mg/kg PO q4–6h until signs resolve (Serotonin syndrome (antidote)). Confirm against the label and the patient before use.

### What is the dose of Cyproheptadine for cats?

Reference doses for Cyproheptadine in cats: 1–4 mg/cat PO q12–24h (Appetite stimulation); 2–4 mg/cat PO q4–6h until signs resolve (Serotonin syndrome (antidote)); 1–2 mg/cat PO q12h (Antihistamine / asthma adjunct). Confirm against the label and the patient before use.

### What is the dose of Cyproheptadine for horses?

Reference doses for Cyproheptadine in horses: 0.25–0.6 mg/kg PO q12h (Headshaking / PPID (adjunct, historical)). Confirm against the label and the patient before use.

### When should Cyproheptadine not be used?

Glaucoma, urinary retention, GI obstruction (anticholinergic). Significant hepatic impairment. Pregnancy (limited data). Concurrent need for serotonergic drug effect (it will antagonise SSRIs/behavioural serotonergics). Known hypersensitivity.

### What are the side effects of Cyproheptadine in animals?

Sedation, lethargy; Anticholinergic effects (dry mouth, urinary retention, constipation); Paradoxical excitement/aggression in some cats; Increased appetite/weight gain (often the desired effect).

## Sources

- Plumb's Veterinary Drug Handbook
- Merck Veterinary Manual, 11th edition
- Papich, Papich Handbook of Veterinary Drugs, 5th edition

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VetMasterJi is a clinical decision-support and education platform for veterinary professionals and students. It does not provide veterinary advice, diagnosis or treatment for specific animals. All drug doses, calculators and differentials are references that must be independently verified before clinical use; the attending registered veterinarian remains solely responsible for every clinical decision.