Metadona
Methadone
Methadone hydrochloride
También conocido como: Dolophine · Methadose · Diskets · Comfortan · Synthadon · Amidine HCl · amidone HCl · methadoni hydrochloridum · Phenadone · Methadone hydrochloride · Metadona
Revisado por el equipo veterinario de VetSheetActualizado 5 abr 2026Referencia veterinaria basada en la evidencia
Evidencia de dosis v13 auditada
Evidencia revisada no calculableEvidencia revisada no calculable (1)
Solo evidencia; no apta para cálculo automático
Anesthesia premedication (extra-label)
Anesthesia premedication (extra-label): Methadone 0.1 – 0.6 mg/kg IV, IM, or SC 70,74
Contexto clínico obligatorio (2)
- NOTE: All listed dosages are based on the methadone HCl salt formulation (10 mg methadone HCl is equivalent to ≈8.9 mg of methadone). Most products are labeled with methadone HCl strength but check before administering to patients.
- Methadone injection should be stored at room temperature of 20°C to 25°C (68°F-77°F) and protected from light. Store vials in the manufacturer’s carton until ready for use.
Las dosis son una referencia clínica para profesionales veterinarios autorizados. Confirme siempre con el prospecto actual y cada paciente individual.
Resumen
La metadona es un agonista de los receptores mu-opioides sintético de alta eficacia, utilizado principalmente como preanestésico y analgésico en perros y gatos. En comparación con la morfina, provoca una liberación de histamina significativamente menor cuando se administra por vía intravenosa y, por lo general, produce menos vómitos y sedación.
Perlas clínicas y ventajas farmacológicas:
- Mecanismo triple: A diferencia de la mayoría de los opioides tradicionales, la metadona no solo es un agonista mu, sino también un antagonista no competitivo de los receptores NMDA y un inhibidor de la recaptación de monoaminas (serotonina y norepinefrina).
- Dolor neuropático: Debido a su antagonismo NMDA, la metadona es particularmente valiosa para tratar el dolor refractario, el dolor neuropático y prevenir la sensibilización central ("wind-up" pain).
- Biodisponibilidad: Tiene una biodisponibilidad oral muy pobre en perros, lo que hace que la administración parenteral (IV, IM, SC) sea la vía estándar en medicina veterinaria.
- Regulación: Es una sustancia controlada de Lista II (C-II) debido a su alto potencial de abuso en humanos.
Mecanismo de acción
Methadone provides analgesia through a unique, multi-modal mechanism of action:
- Mu-Opioid Receptor (MOR) Agonism: Binds to MORs in the central nervous system → inhibits adenylyl cyclase → decreases cAMP → promotes opening of inward-rectifying potassium channels and closing of voltage-gated calcium channels → hyperpolarization of neurons and decreased release of nociceptive neurotransmitters (e.g., Substance P, glutamate).
- NMDA Receptor Antagonism: Acts as a non-competitive antagonist at the N-methyl-D-aspartate (NMDA) receptor → blocks glutamate binding → reduces central sensitization and hyperalgesia.
- Monoamine Reuptake Inhibition: Inhibits the presynaptic reuptake of serotonin (5-HT) and norepinephrine (NE) → increases monoamine concentrations in the synaptic cleft → enhances descending inhibitory pain pathways in the spinal cord.
Seguridad y advertencias
Contraindicaciones
- Late-term pregnancy (due to risks of respiratory depression and stillbirths)
- Known hypersensitivity to methadone
- No specific contraindications available in the monograph, but use with caution in patients with severe respiratory compromise or hepatic impairment.
Efectos adversos
- Panting
- Whining or vocalization
- Defecation
- Constipation
- Bradycardia
- Pronounced CNS excitement (in horses at IV doses ≥ 0.1 mg/kg)
- Respiratory depression (primarily under general anaesthesia)
- Transient excitation (when given IV)
- Salivation (when given via oral transmucosal route in cats due to preservatives)
- Constriction of gastrointestinal sphincters (e.g., pyloric sphincter)
- Reduction in gastrointestinal motility (with prolonged use)
- Neonatal sedation (crosses the placenta)
Precauciones
All opiates should be used with caution in patients with heart failure, hypertension, head injuries, elevated CSF pressures, and in geriatric or severely debilitated patients.
Note: Methadone can increase plasma amylase and lipase values up to 24 hours following administration due to increased biliary tract pressure.
Interacciones farmacológicas
May increase risks for arrhythmias
Potentiates sedative and analgesic effects; combination with medetomidine may cause severe hypoxemia in dogs breathing room air
May increase methadone levels in humans (does not appear to be true for dogs)
May increase risks for arrhythmias
May cause increased CNS or respiratory depression
May increase potential for electrolyte abnormalities
Opiates may decrease diuretic efficacy in CHF patients
May inhibit metabolism of methadone and increase levels in humans (does not appear to be true for dogs)
Potential for severe CNS/behavioral reactions; concomitant use should be avoided
Methadone may enhance neuromuscular blockade
May decrease methadone levels in humans (probably does not affect dogs)
May decrease methadone levels in humans (probably does not affect dogs)
May increase methadone levels
May decrease methadone levels in humans (probably does not affect dogs)
Methadone may exacerbate the effects of tricyclic antidepressants
Opiates may potentiate anticoagulant activity
Methadone may increase zidovudine levels
Increased CNS or respiratory depression
Monitorización
- Analgesic or preanesthetic efficacy
- Respiratory rate and depth (monitor for respiratory depression, especially at higher doses)
- Heart rate (bradycardia)
- CNS depression or excitation
- Respiratory rate and depth (especially under general anaesthesia)
- Pain scores (due to individual variation in response)
- Level of sedation
- Gastrointestinal motility (with prolonged use)
Farmacocinética
Vida media
Absorción
In dogs, methadone has poor oral bioavailability (not significantly affected by ketoconazole or omeprazole). Subcutaneous bioavailability is ~80% with peak levels around 1 hour. In horses, orally administered methadone is well absorbed but rapidly eliminated.
Distribución
Highly lipid-soluble and widely distributed. In humans, it is extensively bound to plasma proteins (60-90%).
Metabolismo
Hepatic. Unlike in humans, CYP3A does not appear to be a major metabolic pathway for methadone biotransformation in dogs. Metabolites are inactive.
Eliminación
In dogs, clearance is about 25-30 mL/kg/min.
Sobredosis
Overdosage may produce profound respiratory and/or CNS depression in most species. Newborns are particularly susceptible. Other toxic effects include cardiovascular collapse, hypothermia, and skeletal muscle hypotonia.
Treatment:
- Naloxone is the reversal agent of choice for treating respiratory depression. In massive overdoses, naloxone doses may need to be repeated because naloxone's effects might diminish before sub-toxic levels of methadone are attained.
- Mechanical respiratory support should be considered in severe cases.
- Dialysis, charcoal hemoperfusion, or forced diuresis do not appear to be beneficial.
Productos disponibles
Formulaciones
- Injection
- Oral tablets
- Dispersible tablets
- Oral solution/liquid concentrate
- Injectable: 10 mg/ml solution (including generic preservative-free preparations)
- Oral: 10 mg tablets
Veterinario
- Comfortan 10 mg/ml solution for injection
- Synthadon 10 mg/ml solution for injection
Etiquetado para humanos
- Methadone HCl Injection: 10 mg/mL
- Methadone HCl Oral Tablets: 5 mg & 10 mg
- Methadone HCl Dispersible Tablets: 40 mg
- Methadone HCl Oral Solution/Liquid Concentrate: 1 mg/mL, 2 mg/mL & 10 mg/mL
- Generic methadone 10 mg tablets
Estado regulador
Authorized veterinary preparations available.
Subject to strict safe custody and register requirements.
Sin datos reguladores para: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Almacenamiento y estabilidad
Store at room temperature and protect from light. Methadone injection is reportedly stable when mixed in a syringe with acepromazine, but is NOT compatible with pentobarbital, phenobarbital, amobarbital, or thiopental.
Información para el cliente
La metadona es un analgésico opioide potente y estrictamente controlado. Cuando se administra mediante inyección, se realiza típicamente en un entorno hospitalario bajo supervisión veterinaria directa.
Si se le receta metadona oral para el control del dolor de su mascota:
- Siga estrictamente la dosis prescrita. No administre más ni menos sin consultar a su veterinario.
-
PELIGRO EXTREMO: Mantenga este medicamento en un lugar seguro, completamente fuera del alcance de niños y otras mascotas. La ingestión accidental por parte de un humano (especialmente un niño) puede causar depresión respiratoria mortal.
- Esté atento a efectos secundarios como sedación leve, jadeo, gemidos o estreñimiento.
- Busque atención veterinaria inmediata si su mascota se muestra extremadamente letárgica, tiene dificultad para respirar o si su respiración se vuelve anormalmente lenta.
La referencia de medicamentos de VetSheet está destinada a profesionales veterinarios autorizados como ayuda para la toma de decisiones clínicas, no como sustituto del criterio profesional ni del prospecto actual del fabricante.