Gabapentin

Gabapentin: Uses, Dosage and Side Effects

Overview

• The exact mechanism of action of gabapentin is unknown, but it appears to bind to a specific modulating protein of voltage-gated calcium channels, thereby reducing the release of excitatory neurotransmitters.
• Gabapentin is structurally related to gamma-aminobutyric acid (GABA) and increases GABA levels in the central nervous system (CNS) without affecting GABA binding, absorption, or release.
• Downregulation of excitatory neurotransmitters in the dorsal horn of the spinal cord or its inhibitory effect on dorsal horn NMDA receptors may be the mechanism of action of the analgesic effect.

Uses of Gabapentin

• Adjunctive therapy for the treatment of seizures is resistant to treatment with conventional therapy, despite the lack of evidence in canines.
• Treatment of chronic pain conditions, including neuropathy and possibly postoperative pain.
• Recent studies have demonstrated its efficacy in enhancing the quality of life in dogs with syringomyelia and reducing the quantity of opioids required in dogs following surgery.

Dose of Gabapentin in Dogs and Cats

Dogs:

• 10–20 mg/kg p.o. q6–8h (starting dose; incremental dose increases are recommended).

Cats:

• 5–10 mg/kg p.o. q8–12h (starting dose; incremental dose increases are recommended).

Side Effects of Gabapentin in Dogs and Cats

• Mild sedation and ataxia are the most frequently reported unwanted effects in canines.
• There have been reports of false-positive results with certain urinary protein assays in humans taking gabapentin.
• Rarely, toxicity to the liver has been reported in human patients.

Contraindications of Gabapentin in Dogs and Cats

• Avoid oral solutions containing xylitol which may be toxic to dogs at higher doses.

Some Notes:

• Aluminium-magnesium antacids reduce the absorption of gabapentin from the GI tract; it is recommended that gabapentin be consumed at least 2 hours after administration of such an antacid.
• It has been reported that cimetidine decreases gabapentin renal clearance, but the product information does not consider this to be clinically significant.
• After multiple dosing, maximal plasma concentrations of gabapentin are typically reached within two hours, and a steady state is reached within one to three days.
• It is partially metabolised by the liver prior to renal excretion, and its half-life is between 3 and 4 hours.
• Humans have experienced seizures after abruptly discontinuing the drug; therefore, tapered withdrawal is recommended.
• Patients with renal impairment, behavioural abnormalities, or severe hepatic disease should be treated with caution.