Meperidine
Meperidine hydrochloride
Also known as: Demerol · Alodan · Centralgine · Dolantina · Dolantine · Dolestine · Dolosal · Pethidine HCl · Isonipecaine · Meperidine hydrochloride · Pethidini hydrochloridum · Pethidinum
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Audited v13 dosing evidence
Structured calculator evidenceAnalgesic (extra-label)
Verified clinician required
- q2-3h
NA
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Meperidine (also known as pethidine) is a synthetic opiate agonist primarily used for analgesia.
Clinical Pearls:
- While historically popular, its use in modern veterinary medicine has significantly declined due to its very short duration of action (<1-2 hours in dogs and cats) and high propensity to cause histamine release and hypotension, especially when administered intravenously.
- Unlike most other opioids, meperidine possesses vagolytic (anticholinergic) and negative inotropic properties, which can lead to tachycardia rather than the bradycardia typically seen with pure mu agonists.
- It is approximately 1/3 to 1/8th as potent as morphine but produces equivalent respiratory depression at equi-analgesic doses.
- It is a C-II controlled substance.
Mechanism of action
Meperidine acts primarily as an agonist at the mu (μ) opioid receptors in the central nervous system (CNS) and peripheral tissues.
- Receptor Binding: Binds to G-protein coupled mu receptors → inhibits adenylate cyclase → decreases intracellular cAMP.
- Ion Channel Modulation: Promotes opening of potassium channels (causing hyperpolarization) and inhibits voltage-gated calcium channels (decreasing neurotransmitter release).
- Analgesia: Inhibits ascending nociceptive pathways and alters the perception of pain.
- Unique Mechanisms: Exhibits anticholinergic (vagolytic) effects and can cause direct mast cell degranulation leading to histamine release.
Safety & warnings
Contraindications
- Hypersensitivity to narcotic analgesics
- Patients receiving monamine oxidase inhibitors (MAOIs)
- Diarrhea caused by a toxic ingestion (until toxin is eliminated)
- Envenomations from Centruroides scorpion species, Gila monsters, or Mexican beaded lizards
- Intravenous (IV) administration
- Animals at risk from histamine release (e.g., skin allergies, asthma, mast cell tumours)
Adverse effects
- Respiratory depression
- Histamine release
- Bronchoconstriction (dogs)
- CNS depression
- Nausea and vomiting
- Decreased intestinal peristalsis
- Mydriasis (dogs)
- Salivation (especially cats)
- Physical dependence (chronic use)
- Tachycardia with PVCs (horses)
- Profuse sweating (horses)
- Hyperpnea (horses)
- Severe hypotension (if given IV rapidly)
- Hypotension (especially if given IV)
- Local urticaria (after IM injection)
- Dry mouth
- Pain on IM injection (due to volume)
- Neonatal sedation (if given to bitches prior to parturition)
Precautions
Important Administration Note: Many clinicians state meperidine should NOT be administered intravenously. If given IV, it must be given very slowly to avoid severe hypotension and histamine release. It may also be irritating when given SC.
- Extreme Caution: Patients with respiratory disease or acute respiratory dysfunction (e.g., pulmonary edema secondary to smoke inhalation).
- Caution: Hypothyroidism, severe renal insufficiency, adrenocortical insufficiency (Addison's disease), geriatric or severely debilitated patients.
- Caution: Head injuries or increased intracranial pressure, and acute abdominal conditions (e.g., colic) as it may obscure diagnosis.
- Equine Note: May potentiate intestinal obstruction secondary to reduced intestinal motility.
Drug interactions
May cause increased CNS or respiratory depression when used with meperidine.
Opiates may decrease efficacy in CHF patients.
Meperidine may enhance INH adverse effects.
Contraindicated. Can cause severe opiate overdose signs; avoid meperidine for at least 14 days after receiving MAOIs.
Meperidine may enhance neuromuscular blockade.
Meperidine may exacerbate the effects of tricyclic antidepressants.
Opiates may potentiate anticoagulant activity.
Increased CNS or respiratory depression
Serious interaction resulting in coma, convulsions, and hyperpyrexia
Monitoring
- Respiratory rate and depth
- CNS level of depression or excitation
- Blood pressure (especially with IV use)
- Analgesic activity
- Pain score
- Heart rate
- Signs of histamine release (urticaria, bronchoconstriction)
Pharmacokinetics
Half-life
Absorption
Generally well absorbed orally, but a marked first-pass effect limits oral effectiveness. Peak analgesic effects occur between 30-60 minutes after IM or SC injection, with IM having a slightly faster onset.
Distribution
Widely distributed. Enters human breast milk at concentrations slightly higher than serum.
Metabolism
Metabolized primarily in the liver (mostly hydrolysis with some conjugation).
Elimination
Approximately 5% is excreted unchanged in the urine.
Overdose
Overdosage may produce profound respiratory and/or CNS depression. Other effects can include cardiovascular collapse, hypothermia, and skeletal muscle hypotonia.
- Species Differences: Some species (especially cats) may demonstrate CNS excitability (hyperreflexia, tremors) and seizures at doses >20 mg/kg.
- Treatment: Naloxone is the agent of choice for respiratory depression. In massive overdoses, naloxone doses may need to be repeated, as its effects can diminish before subtoxic levels of meperidine are attained. Mechanical respiratory support should be considered. Pentobarbital has been suggested for CNS excitement/seizures in cats, but extreme caution is required as barbiturates and narcotics have additive respiratory depressant effects.
Available products
Formulations
- Injection
- Tablets
- Syrup/Oral Solution
- Injectable: 10-50 mg/ml solutions (50 mg/ml is most commonly used in veterinary practice)
Veterinary
- Pethidine 50 mg/ml injection
Human-labeled
- Meperidine HCl Injection: 25 mg/mL, 50 mg/mL, 75 mg/mL, 100 mg/mL
- Meperidine HCl Tablets: 50 mg, 100 mg
- Meperidine HCl Syrup/Oral Solution: 50 mg/5 mL
- Demerol
- Meperidine injection
Regulatory status
POM (Prescription Only Medicine)
POM-V CD SCHEDULE 2
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Stable at room temperature. Avoid freezing the injectable solution and protect from light during storage. Does not exhibit significant adsorption to PVC IV bags or tubing.
Client information
Important: Meperidine is a strong prescription pain medication (opioid) that is typically only used in a hospital setting under direct veterinary supervision.
- Short-acting: This medication wears off very quickly in pets (often in less than an hour), so it is usually given as an injection during procedures rather than sent home.
- Side Effects: May cause sleepiness, nausea, or drooling. If given by mouth, the liquid or tablets can be irritating to the mouth, especially in cats.
- Safety: Never give your pet human pain medications or leftover meperidine without strict veterinary guidance, as overdoses can cause life-threatening breathing problems.
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.