Overview
Gabapentin is an anticonvulsant and neuropathic pain agent structurally related to gamma-aminobutyric acid (GABA). It is used primarily for partial seizures and neuropathic pain conditions.
Mechanism of Action
Gabapentin binds with high affinity to the α2δ subunit of voltage-gated calcium channels in the central nervous system. This results in: Decreased calcium influx into nerve terminals Reduced release of excitatory neurotransmitters (e.g., glutamate, substance P) Decreased neuronal hyperexcitability Gabapentin does not bind directly to GABA-A or GABA-B receptors and does not significantly affect GABA metabolism.
Indications
- Adjunctive therapy in the treatment of partial seizures (with and without secondary generalization) in adults and pediatric patients
- Postherpetic neuralgia (PHN)
- (Extended-release formulations may have additional specific indications depending on product labeling)
Dosage
Postherpetic Neuralgia (Adults): Day 1: 300 mg once daily Day 2: 300 mg twice daily Day 3: 300 mg three times daily May increase as needed up to 1,800 mg/day (divided doses) Partial Seizures (Adults): Initial: 300 mg three times daily Maintenance: 900–1,800 mg/day in three divided doses Maximum: up to 3,600 mg/day (based on clinical response and tolerability) Pediatric (3–12 years for partial seizures): 10–15 mg/kg/day initially Maintenance: 25–35 mg/kg/day in divided doses Renal Impairment: Dose adjustment required based on creatinine clearance
Contraindications
- Hypersensitivity to gabapentin or any component of the formulation
Side Effects
- Dizziness
- Somnolence
- Ataxia
- Fatigue
- Peripheral edema
- Nystagmus
- Serious (less common):Suicidal ideation
- Serious (less common):Hypersensitivity reactions (e.g., DRESS)
- Serious (less common):Respiratory depression (especially with opioids)
Interactions
- Opioids (e.g., morphine): Increased CNS depression and respiratory depression risk
- Antacids containing aluminum or magnesium: Reduce gabapentin absorption (separate administration by at least 2 hours)
- Minimal CYP450 interactions
Counseling Points
- Causes drowsiness. Taper off slowly. Prescription only.