Hydromorphone: veterinary dose and monograph

At a glance

Drug class

Analgesic

Also known as

Dilaudid, Hydromorphone HCl

Species with doses

Dogs, Cats, Horses, Rabbits, Ferrets and Reptiles

General dose range

0.05–0.2 mg/kg IV q2–6h (or CRI) — check the species tables for the indication

Routes

IV, IM, Epidural, SC

Last reviewed

1 October 2026

Indications

• Moderate–severe acute / post-operative pain
• Premedication and balanced anaesthesia (opioid component)
• Trauma / emergency analgesia
• Analgesic CRI in hospitalised patients

Hydromorphone 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

• Acute / post-op pain: Papich 5e: 0.1–0.2 mg/kg IV repeated q2h, or 0.22 mg/kg IM/SC q4–6h; 0.1 mg/kg with acepromazine as a premedicant. Plumb’s p.623: 0.05–0.2 mg/kg IV, IM or SC q2–4h (Hansen; Hardie); 0.1 mg/kg IV or SC q2h (KuKanich 2008). Vomiting, panting and bradycardia are common; hyperthermia can occur.
• Analgesic CRI: Papich 5e: 0.01 mg/kg/h IV. Plumb’s p.623 (KuKanich 2008): 0.03 mg/kg/h based on pharmacokinetics.

Cats

• Acute / post-op pain: Papich 5e: 0.1–0.2 mg/kg SC or IM, or 0.05–0.1 mg/kg IV, q2–6h. Plumb’s p.623: 0.05–0.1 mg/kg IM, IV or SC q2–6h (Wagner 2002); moderate–severe pain 0.08–0.3 mg/kg (Mathews). Opioid-associated hyperthermia in cats — monitor temperature.
• Epidural analgesia: Papich 5e: 0.05 mg/kg diluted in saline to 0.2 mL/kg (1 mL per cat).

Horses

• Epidural analgesia: Papich 5e: 0.04 mg/kg diluted in 0.9% saline to 20 mL. No systemic horse dose reported.

Rabbits

• Premedication / post-op analgesia: Plumb’s p.623 (Lichtenberger 2006): rabbits 0.05–0.1 mg/kg IV; post-op CRI after 0.05 mg/kg IV load at 0.05–0.1 mg/kg/h.

Ferrets

• Premedication / post-op analgesia: Plumb’s p.623 (Lichtenberger 2006): pre-op 0.05–0.1 mg/kg IV; post-op CRI after 0.05 mg/kg IV load at 0.05–0.1 mg/kg/h.

Reptiles

• Analgesia: Carpenter's 6th ed (Reptile analgesic table): 0.5–1 mg/kg SC q24h (red-eared sliders); 0.5 mg/kg SC (bearded dragons — PK supports q24h). Mu-opioid — more reliable reptile analgesia than butorphanol.

Contraindications

Severe respiratory compromise without support. Head trauma with raised ICP (relative). Use reduced doses in geriatric/debilitated/hypovolaemic patients. Concurrent MAOIs/selegiline. Known opioid hypersensitivity.

Species-specific warnings

Cats: Cats are prone to opioid hyperthermia and dysphoria — use lower doses and monitor temperature after dosing.

Adverse effects

• Dose-dependent respiratory depression
• Bradycardia (vagal — anticholinergic-responsive)
• Vomiting/nausea, panting (dogs)
• Hyperthermia in cats; sedation or dysphoria
• Reduced GI motility

Drug interactions

• Other CNS depressants/anaesthetics/opioids: additive respiratory and CNS depression — reduce doses
• MAO inhibitors / selegiline: serotonergic/excitatory reaction
• Anticholinergics: used to manage opioid bradycardia
• Phenothiazines (acepromazine): enhanced sedation/hypotension (often combined deliberately)

Pregnancy and lactation

Crosses the placenta — neonatal respiratory depression near parturition (have naloxone for neonates). Used peri-operatively when needed.

Monitoring

• Respiratory rate/effort and SpO2/capnography
• Heart rate (bradycardia) and blood pressure
• Temperature — especially cats (hyperthermia)
• Sedation/analgesia/dysphoria scoring; controlled-drug records

Toxicity and overdose

Overdose: marked respiratory depression/apnoea, profound sedation/coma, bradycardia, hypotension, miosis (dogs). Cats may show hyperthermia and excitation. Reversible with naloxone.

Management: Antidote: naloxone 0.01–0.04 mg/kg IV/IM, repeated as needed (may need re-dosing/CRI as the opioid can outlast naloxone). Support ventilation/oxygenation (priority), treat bradycardia with anticholinergics, IV fluids and warmth; actively COOL cats with opioid hyperthermia.

Clinical pearls

• A strong, reliable, cardiovascularly stable opioid — an excellent morphine alternative with less histamine release (safer IV)
• Always have naloxone and the means to ventilate before dosing potent opioids
• Watch cats for opioid HYPERTHERMIA (check temperature post-dose) and dose at the lower end
• Bradycardia is vagal and anticholinergic-responsive; respiratory depression is the dangerous effect
• Account for every dose — controlled substance

Mechanism of action

Pure mu-opioid receptor agonist acting in the brain and spinal cord (dorsal horn) to inhibit ascending nociceptive transmission and activate descending inhibition (G-protein coupling → reduced cAMP, decreased neuronal excitability and neurotransmitter release). Greater potency and less histamine release than morphine, with similar efficacy.

Formulations and products

• Injection 2 mg/mL
• Injection 10 mg/mL (concentrated)
• Dilaudid / Hydromorphone — 2 mg/mL / 10 mg/mL injection; tablets, Injection / tablet (human-label)

Storage

Injection: 15–30 °C, protect from light; SECURE controlled-drug storage and accountability records.

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 analgesics

• Codeine
• Dipyrone (Metamizole)
• Fentanyl
• Gabapentin
• Lidocaine HCl
• Methadone
• Morphine Sulfate
• Nalbuphine

Frequently asked questions