Gabapentin
Gabapentin is a structural analogue of gamma-aminobutyric acid (GABA) widely utilized in veterinary medicine primarily for its **neuropathic analgesic** and **anticonvulsant** properties. * **Analgesia**: Highly effective for chronic, maladaptive, and neuropathic pain (e.g., osteoarthritis, intervertebral disc disease, cancer pain). Often used as part of a multimodal analgesic protocol. * **Seizure Management**: Used as an adjunctive antiepileptic drug (AED) for refractory or complex partial seizures, though its efficacy as a sole agent is limited. * **Behavioral/Anxiolytic**: Increasingly used off-label in cats and dogs to reduce fear, anxiety, and stress (FAS) prior to veterinary visits or stressful events.
Mecanismo: Despite its name, gabapentin does *not* bind to GABA receptors, nor does it affect GABA synthesis or uptake. * Binds selectively to the **α2-δ (alpha-2-delta) subunit** of **voltage-gated calcium channels (CaV)** in the central nervous system. * **Inhibition of Calcium Influx** → Decreased presynaptic calcium currents. * **Reduced Neurotransmitter Release** → Suppresses the release of excitatory neurotransmitters including **glutamate**, **substance P**, and **norepinephrine** in the dorsal horn of the spinal cord. * This dampens neuronal excitability, effectively preventing **allodynia** (pain from non-noxious stimuli) and **hyperalgesia** (exaggerated pain response).
Dosificación por especie
- Ancillary therapy of refractory seizures · 5-10 mg/kg · PO · q8-12h
- Ancillary therapy of refractory seizures · 5 mg/kg · PO · three times daily
- Ancillary therapy of refractory seizures · 10-30 mg/kg · PO · q8-12h
- Analgesic · 1.25-10 mg/kg · PO · q24h
- Adjunctive treatment of chronic or cancer pain · 3 mg/kg · PO · once a day
- Adjunctive analgesia associated with neuropathic pain · 2.5-5 mg/kg · PO · q12h · Author starts at 5 mg/kg and increases (up to 10 mg/kg) if no effect seen in two hours. Wean off slowly. Reduce in renal insufficiency.
- Analgesic · 5-10 mg/kg · PO · 2-3 times a day · Most VIN consultants recommend this dose.
- Analgesic · 50 mg (total dose) per cat · PO · 1-3 times a day
- Adjunctive seizure therapy / Chronic pain · 5-10 mg/kg · PO · q8-12h · starting dose; incremental dose increases are recommended
- Ancillary therapy of refractory seizures · 10-20 mg/kg · PO · q6-8h · Author notes gabapentin is the least effective of the newer antiepileptic drugs, particularly in dogs.
Vías de administración
Contraindicaciones
- Hypersensitivity to gabapentin
- Use of xylitol-containing human oral solutions in dogs
- Oral solutions containing xylitol (highly toxic to dogs)
Efectos adversos
- Sedation
- Ataxia
- Dizziness (humans)
- Somnolence
- Peripheral edema (humans)
- Withdrawal-precipitated seizures (if abruptly discontinued)
- Increased rate of pancreatic adenocarcinoma (noted in male rats)
- Mild sedation
- False-positive urinary protein tests (reported in humans)
- Hepatic toxicity (rare, reported in humans)
Interacciones farmacológicas
- Antacids · Oral antacids given concurrently may decrease oral bioavailability of gabapentin by 20%; separate doses by at least 2 hours.
- Hydrocodone · Co-administration may increase gabapentin AUC and efficacy/adverse effects. Gabapentin may reduce hydrocodone AUC, potentially reducing its effectiveness.
- Morphine · May increase gabapentin levels.
- Antacids (containing aluminium and magnesium) · Reduced absorption of gabapentin from the GI tract. Administer gabapentin at least 2 hours after antacids. · moderate
- Cimetidine · Reduced renal clearance of gabapentin (not considered clinically important). · minor
Monitorización
- Clinical efficacy (reduction in pain scores or seizure frequency)
- Adverse effects (sedation, ataxia)
- Renal function (in patients with pre-existing disease)
- Clinical response (pain scores, seizure frequency)
- Renal and hepatic function in compromised patients
Sobredosis
In humans, massive overdoses (up to 49 grams) have been reported without fatality. * **Clinical Signs**: Ataxia, lethargy, somnolence, vomiting, and diarrhea. * **Xylitol Toxicity Risk**: The human oral solution contains 300 mg/mL of xylitol. Doses as low as 0.33 mL/kg of this solution can cause severe hypoglycemia or hepatotoxicity in dogs. * **Treatment**: Primarily supportive. General decontamination (emesis, activated charcoal, cathartics) if caught early. The drug can be removed via hemodialysis. If xylitol toxicity is suspected secondary to the human liquid formulation, aggressive treatment for hypoglycemia and liver protection is required; contact an animal poison control center.
La referencia de fármacos de VetSheet está destinada a veterinarios colegiados como apoyo a la decisión clínica, no sustituye el juicio profesional ni la ficha técnica vigente del fabricante.