Cyproheptadine: veterinary dose and monograph

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

• 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

• 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

• 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

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

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.

Other hormones, emergency drugs, supplements and other drugs

• Cloprostenol
• Cyanocobalamin (Vitamin B12)
• Cyclophosphamide
• Cyclosporine
• Dantrolene
• Deferoxamine (Desferrioxamine)
• Deslorelin
• Desmopressin (DDAVP)

Frequently asked questions