Hydromorphone

Hydromorphone hydrochloride

Opiate Agonist / AnalgesicIVIMSCPORectalDogsCatsSmall MammalsFerrets

Also known as: Dilaudid-HP · Exalgo · Palladone · dihydromorphinone hydrochloride · Dolonovag · Hydal · HydroStat IR · Opidol · Sophidone

Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference

0.08-0.2 mg/kg IV, IM, or SCIV/IM/SC· Not specified

Body weight— 🐕

Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.

Dosing by species

🌎 NA — North America🌍 EU — Europe

Dogs

Indication	Dose	Route	Frequency	Duration	Region
As an analgesic	0.1 mg/kg IV or SC q2h or as a CRI at 0.03 mg/kg/hr	IV/SC	q2h or CRI	—	🌎 NA
For cancer pain	0.08-0.2 mg/kg IV, IM, or SC	IV/IM/SC	Not specified	—	🌎 NA
As an analgesic	0.05-0.2 mg/kg IV, IM, SC q2-4h	IV/IM/SC	q2-4h	—	🌎 NA
As an analgesic	0.2-0.6 mg/kg PO q6-8h	PO	q6-8h	—	🌎 NA
For perioperative pain	0.1-0.2 mg/kg IV, IM, SC q2-4h	IV/IM/SC	q2-4h	—	🌎 NA
As a premed prior to moderately painful procedures	0.1 mg/kg	Not specified	Once	—	🌎 NA
As a sedative/restraint agent for fractious or aggressive dogs	0.1-0.2 mg/kg mixed with acepromazine (0.05 mg/kg) IM	IM	Once	—	🌎 NA
As an alternate induction method (especially in critical patients)	0.05-0.2 mg/kg IV, slowly to effect followed by diazepam 0.02 mg/kg IV	IV	Once	—	🌎 NA

As an analgesic: Suggested doses based on pharmacokinetic study
As a premed prior to moderately painful procedures: May be combined with acepromazine (0.02-0.05 mg/kg) in young, healthy patients.
As a sedative/restraint agent for fractious or aggressive dogs: Maximal effect usually reached in about 15 minutes, but an additional wait of another 15 minutes may be necessary in some dogs.
As an alternate induction method (especially in critical patients): Do not mix two drugs together. Positive pressure ventilation likely necessary. Treat bradycardia with glycopyrrolate or atropine if needed.

Cats

Indication	Dose	Route	Frequency	Duration	Region
As an analgesic	0.05-0.1 mg/kg IM, IV or SC q2-6 hours	IM/IV/SC	q2-6h	—	🌎 NA
For cancer pain	0.08-0.2 mg/kg IV, IM, or SC	IV/IM/SC	Not specified	—	🌎 NA
For moderate to severe pain	0.08-0.3+ mg/kg IV, IM or SC q2-6 hours	IV/IM/SC	q2-6h	—	🌎 NA
As a premed prior to moderately painful procedures	0.1 mg/kg	Not specified	Once	—	🌎 NA
As an alternate induction method (especially in critical patients)	0.05-0.2 mg/kg IV, slowly to effect followed by diazepam 0.02 mg/kg IV	IV	Once	—	🌎 NA

As a premed prior to moderately painful procedures: May be combined with acepromazine (0.05-0.2 mg/kg) in young, healthy patients.
As an alternate induction method (especially in critical patients): Do not mix two drugs together. Positive pressure ventilation likely necessary.

Small Mammals

Indication	Dose	Route	Frequency	Duration	Region
As a pre-op (Rabbits)	0.05-0.1 mg/kg IV	IV	Once	—	🌎 NA
As a CRI post-op (Rabbits)	0.05 mg/kg IV loading dose, then 0.05-0.1 mg/kg/hr	IV	CRI	—	🌎 NA

Ferrets

Indication	Dose	Route	Frequency	Duration	Region
As a pre-op	0.05-0.1 mg/kg IV	IV	Once	—	🌎 NA
As a CRI post-op	0.05 mg/kg IV loading dose, then 0.05-0.1 mg/kg/hr	IV	CRI	—	🌎 NA

Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.

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Overview

Hydromorphone is a potent, semi-synthetic pure mu-opioid receptor agonist used extensively in veterinary medicine as a sedative, restraining agent, analgesic, and preanesthetic.

Key clinical features include:

Potency: Approximately 5 times more potent than morphine on a per-weight basis, and roughly equipotent to oxymorphone.
Advantages over Morphine: Generally causes less sedation, minimal histamine release following intravenous administration, and rarely induces significant vasodilation or hypotension.
Clinical Utility: Rapidly replacing oxymorphone in veterinary practice due to comparable analgesic efficacy and duration of action, but at a significantly lower cost.
Regulatory Status: It is a Schedule II (C-II) controlled substance due to its high potential for abuse and physical dependence.

Mechanism of action

Hydromorphone exerts its effects by binding to opioid receptors, primarily the mu (μ) receptors, with some affinity for delta (δ) receptors.

Mechanism pathway: Agonist binding to mu-receptors in the CNS (limbic system, spinal cord, thalamus, midbrain) and peripheral tissues (GI tract, smooth muscle) → activation of G-proteins → inhibition of adenylate cyclase → decreased intracellular cAMP → opening of potassium channels (causing hyperpolarization) and closing of voltage-gated calcium channels → decreased presynaptic release of excitatory neurotransmitters (e.g., Substance P, glutamate) → profound analgesia and altered pain perception.

Secondary effects include respiratory depression (decreased sensitivity of the respiratory center to CO2), antitussive activity, and increased GI sphincter tone leading to decreased motility.

Safety & warnings

Contraindications

Hypersensitivity to narcotic analgesics
Diarrhea caused by toxic ingestion (until toxin is eliminated)
Prior to GI obstructive surgery (due to vomiting risk)
Patients stung by scorpion species Centruroides sculpturatus Ewing and C. gertschi Stahnke (may potentiate venom)

Adverse effects

Dogs: Nausea, vomiting, defecation, panting, vocalization, sedation, CNS depression, respiratory depression, bradycardia, decreased GI motility (constipation with chronic use)
Cats: Nausea, ataxia, hyperesthesia, hyperthermia, behavioral changes (mania/excitement if given without tranquilization)
Mild histamine release (infrequent compared to morphine)

Precautions

Black Box Warning / Extreme Caution: Use with extreme caution in patients with respiratory disease, acute respiratory dysfunction, head injuries, increased intracranial pressure, and acute abdominal conditions (e.g., colic) as it may obscure diagnosis.

Vomiting Risk: Contraindicated as a preanesthetic in animals with suspected gastric dilation, volvulus, or intestinal obstruction.
Systemic Disease: Use cautiously in hypothyroidism, severe renal insufficiency (acute uremia), adrenocortical insufficiency (Addison's), and severe hepatic disease (prolonged duration of action).
Cardiovascular: Can cause bradycardia; use cautiously in patients with preexisting bradyarrhythmias.
Feline Hyperthermia: Can cause self-limiting hyperthermia in cats. High doses in cats should be combined with a tranquilizer to prevent bizarre behavioral changes.
Vulnerable Populations: Geriatric, debilitated, or neonatal patients may be more susceptible and require lower dosages.

Drug interactions

Butorphanol, Nalbuphine

Potentially could antagonize opiate effects

CNS Depressants

Additive CNS depression effects possible

Diuretics

Opiates may decrease diuretic efficacy in CHF patients

Monoamine Oxidase Inhibitors (e.g., amitraz, selegiline)

Severe and unpredictable opiate potentiation; not recommended if MAOI used within 14 days

Skeletal Muscle Relaxants

Hydromorphone may enhance muscle relaxant effects

Phenothiazines

May antagonize analgesic effects and increase risk for hypotension

Tricyclic Antidepressants (clomipramine, amitriptyline)

Hydromorphone may exacerbate the effects of tricyclic antidepressants

Warfarin

Opiates may potentiate anticoagulant activity

Monitoring

Respiratory rate and depth (pulse oximetry highly recommended)
CNS level of depression or excitation
Blood pressure (especially with IV use)
Cardiac rate (monitor for bradycardia)
Analgesic efficacy

Pharmacokinetics

Half-life

CatsProlonged (due to glucuronidation deficiency)Dogs35 minutes to 1 hour (route and dose dependent)

Absorption

Absorbed when given by IV, IM, SC, and rectal routes. Peak levels occur between 10-30 minutes after SC dosing in dogs.

Distribution

High volume of distribution in dogs (> 4 L/kg with both IV and SC dosing).

Metabolism

Metabolized in the liver, primarily by glucuronidation. Cats are deficient in this metabolic pathway, leading to prolonged half-lives.

Elimination

The glucuronidated metabolite is excreted by the kidney.

Overdose

Massive overdoses may produce profound respiratory and/or CNS depression in most species.

Other potential effects include:

Cardiovascular collapse
Hypothermia
Skeletal muscle hypotonia
Mania (especially in cats)

Treatment:

Naloxone is the specific reversal agent of choice for treating respiratory depression.
In massive overdoses, naloxone doses may need to be repeated, as naloxone's duration of action may be shorter than that of hydromorphone.
Mechanical respiratory support should be considered in cases of severe respiratory depression.
Provide supportive care as needed.

Available products

Formulations

Powder for injection (lyophilized)
Oral tablets
Oral capsules (extended-release)
Oral liquid
Suppositories

Veterinary

None

Human-labeled

Hydromorphone HCl Injection: 1 mg/mL, 2 mg/mL, 4 mg/mL, 10 mg/mL (Dilaudid, Dilaudid-HP, generic)
Hydromorphone HCl Powder for Injection, lyophilized: 250 mg (Dilaudid-HP)
Hydromorphone HCl Oral Tablets: 2 mg, 4 mg, 8 mg (Dilaudid, generic)
Hydromorphone HCl Oral Capsules (extended-release): 8 mg, 12 mg, 16 mg (Exalgo)
Hydromorphone HCL Oral Liquid: 1 mg/1 mL (Dilaudid, generic)
Hydromorphone Suppositories: 3 mg (Dilaudid, generic)

Regulatory status

No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU

Storage & stability

Injection should be stored at room temperature and protected from light. A slight yellowish tint does not indicate loss of potency. Stable for at least 24 hours when mixed with commonly used IV fluids if protected from light. Tablets should be stored at room temperature in tight, light-resistant containers. Suppositories should be kept in the refrigerator.

Client information

Hydromorphone is a potent opioid pain medication.

Supervision: When given by injection, this medication is typically used in a hospital setting under direct veterinary supervision.
Oral Use at Home: If sent home with oral tablets or liquid, keep this medication in a secure location out of reach of children and other pets. It is a strictly controlled substance.
What to Expect: Your pet may appear sedated or sleepy. In dogs, panting and whining are common side effects and do not necessarily mean the pet is in pain. Cats may occasionally act restless or have a slightly elevated body temperature.
Side Effects to Watch For: Monitor for severe lethargy, extreme difficulty breathing, or severe constipation. Contact your veterinarian if these occur.
Do Not Share: Never give this medication to another pet or a human, as it can be fatal if used incorrectly.

VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.