Pethidine (Meperidine): veterinary dose and monograph

At a glance

Drug class

Analgesic

Also known as

Meperidine, Demerol

Species with doses

Dogs, Cats, Horses, Rabbits and Ferrets

General dose range

3–5 mg/kg IM q1–2h (short-acting) — check the species tables for the indication

Routes

IM, SC

Last reviewed

1 October 2026

Indications

• Premedication (sedation + analgesia) before anaesthesia
• Short-term acute / post-operative pain
• Spasmodic / obstructive colic pain in horses (antispasmodic opioid)
• Analgesia where a brief-acting opioid is desirable

Pethidine (Meperidine) 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

• Premed / acute pain: Plumb’s p.785: 5–10 mg/kg IM or SC, effect 30–60 min (Mama 2002); perioperative 3–5 mg/kg IM or SC, 1–2 h (Pascoe 2000); premed 3–4 mg/kg IM, post-op 1–2 mg/kg IM (Trim 2008). Papich 5e: 5–10 mg/kg IV or IM every 2–3 h. Prefer IM/SC — IV causes histamine release and hypotension.

Cats

• Premed / acute pain: Papich 5e: 3–5 mg/kg IV or IM every 2–4 h. Plumb’s p.785: 3–5 mg/kg IM or SC, 1–2 h (Pascoe 2000); 2–5 mg/kg (Mama 2002); premed 3–4 mg/kg IM. One author does not recommend it for cats (Scherk 2003).

Horses

• Spasmodic colic / analgesia: Plumb’s p.785: 2–4 mg/kg IM or IV — IV may cause excitement and hypotension (Jenkins 1987); 500 mg total IV slowly or 1000 mg IM (Booth 1988). Pre-treat with acepromazine or xylazine to limit excitement; opioids can mask signs of mild colic. (500 mg total IV ≈ 1 mg/kg and 1000 mg IM ≈ 2 mg/kg for a 500 kg horse.) Papich 5e gives no large-animal dose.

Rabbits

• Moderate pain: Plumb’s p.785 (Ivey & Morrisey 2000): rabbits 5–10 mg/kg SC or IM every 2–3 h.

Ferrets

• Analgesia: Plumb’s p.785 (Williams 2000): 5–10 mg/kg SC or IM every 2–3 hours.

Contraindications

IV administration (causes histamine release → hypotension, tachycardia — give IM/SC). Concurrent MAO inhibitors / selegiline (serotonin syndrome, can be fatal). Severe respiratory compromise without support. Reduce in geriatric/debilitated patients. Known opioid hypersensitivity.

Species-specific warnings

Cats: Use lower doses — cats can show opioid excitation/dysphoria. Still IM/SC, never IV.

Horses: Useful for colic but high doses can cause excitation; combine with sedation and reassess for surgical colic.

Adverse effects

• Histamine release and hypotension if given IV
• Respiratory depression (dose-related)
• Sedation; excitation/dysphoria in cats and horses at high dose
• Reduced GI motility (less than morphine)
• Short duration — analgesic gaps if not re-dosed

Drug interactions

• MAO inhibitors / selegiline: contraindicated — severe, potentially fatal serotonin/excitatory reaction
• Other CNS depressants: additive sedation/respiratory depression
• Serotonergic drugs (SSRIs, tramadol): serotonin-syndrome risk
• Phenothiazines (acepromazine): enhanced sedation/hypotension

Pregnancy and lactation

Crosses the placenta — neonatal respiratory depression if given near parturition (have naloxone for neonates). Short-term peri-operative use is otherwise common.

Monitoring

• Respiratory rate/effort and SpO2
• Blood pressure (especially watching for the IV-histamine error)
• Sedation/analgesia level — re-dose for its short duration
• Controlled-drug accountability

Toxicity and overdose

Overdose: respiratory depression, sedation/coma, hypotension. IV injection provokes dangerous histamine release. Repeated/high dosing accumulates the excitatory metabolite normeperidine, which can cause tremors and seizures (more relevant with chronic use, which is not typical in veterinary practice).

Management: Antidote: naloxone 0.01–0.04 mg/kg IV/IM, repeated as needed. Support ventilation/oxygenation and blood pressure (IV fluids); treat histamine-mediated hypotension with fluids ± vasopressor. Manage normeperidine-related tremor/seizures with benzodiazepines (naloxone does not reverse those).

Clinical pearls

• Remember it as the "short and IM-only" opioid — never give pethidine IV (histamine release)
• Its mild antispasmodic action makes it a classic choice for equine spasmodic colic pain
• Short duration is a feature for premed but a pitfall for ongoing pain — re-dose or switch to a longer opioid
• Strictly avoid with selegiline/MAOIs — the combination can be fatal
• Keep naloxone available whenever giving potent opioids

Mechanism of action

Agonist at mu (and some kappa) opioid receptors, inhibiting nociceptive transmission in the spinal cord and brain and activating descending inhibition. It also has mild local-anaesthetic and anticholinergic/spasmolytic actions, which reduce smooth-muscle spasm relative to other opioids. Its metabolite normeperidine is neuro-excitatory and accumulates with repeated dosing.

Formulations and products

• Injection 50 mg/mL
• Pethidine injection (vet/hospital) (Various (controlled)) — 50 mg/mL, Injection
• Pethidine Hydrochloride — 50 mg/mL ampoule, Injection (human-label)

Storage

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

• Methadone
• Morphine Sulfate
• Nalbuphine
• Paracetamol (Acetaminophen)
• Pregabalin
• Tramadol

Frequently asked questions