BSN Tracker

gabapentin

Brand: Neurontin, Gralise, Horizant

⚠ BBW Beers Criteria Prototype Drug
Drug Class: antiepileptic / analgesic
Drug Family: antiepileptic
Subclass: GABA analogue
Organ Systems: cns

Mechanism of Action

Binds to the alpha-2-delta subunit of presynaptic voltage-gated calcium channels, reducing calcium influx and decreasing release of excitatory neurotransmitters (glutamate, substance P, norepinephrine).

alpha-2-delta subunit of voltage-gated calcium channels

Indications

  • focal-onset seizures (adjunct)
  • postherpetic neuralgia
  • restless leg syndrome (Horizant formulation)
  • off-label: neuropathic pain, fibromyalgia, anxiety

Contraindications

  • known hypersensitivity to gabapentin

Adverse Effects

Common

  • somnolence
  • dizziness
  • ataxia
  • fatigue
  • peripheral edema
  • weight gain

Serious

  • respiratory depression (risk with opioids/CNS depressants)
  • multiorgan hypersensitivity
  • suicidal ideation
  • drug abuse/dependence

Pharmacokinetics (ADME)

Absorption Non-linear, saturable absorption (bioavailability decreases with higher doses: ~60% at 300 mg, ~33% at 1600 mg)
Distribution Not protein-bound (<3%); Vd ~0.65 L/kg
Metabolism Not metabolized; excreted unchanged
Excretion Entirely renal; significant dose adjustment required for CrCl <60 mL/min
Half-life 5–7 hours
Onset Variable; 2–3 days for analgesic effect
Peak 2–3 hours
Duration 8 hours (requires TID dosing)
Protein Binding <3%
Vd ~0.65 L/kg

Drug Interactions

Drug / Agent Mechanism Severity
opioids additive CNS/respiratory depression; pharmacokinetic interaction with hydrocodone major
antacids (aluminum/magnesium) reduce gabapentin absorption by ~20% minor
morphine morphine increases gabapentin AUC by 44% moderate

Nursing Considerations

  1. Dose must be adjusted for renal function; obtain baseline and periodic serum creatinine — major dose reductions required when CrCl <60 mL/min
  2. Monitor for respiratory depression especially when combined with opioids, benzodiazepines, or other CNS depressants
  3. Taper dose over at least 1 week on discontinuation to minimize withdrawal seizure risk
  4. Assess for misuse potential; gabapentin is scheduled in some states due to increasing reports of abuse, particularly in combination with opioids

Clinical Pearls

  • Gabapentin absorption is dose-dependent and saturable — spreading doses throughout the day or using the Gralise extended-release formulation improves bioavailability at higher doses
  • Despite its name, gabapentin does not act on GABA receptors — it binds to voltage-gated calcium channel subunits, making it distinct mechanistically from benzodiazepines and barbiturates

Safety Profile

Pregnancy use-with-caution
Lactation use-with-caution
Renal Adjustment Required
Hepatic Adjustment Not required
TDM Not required

Concordance Terms

Cross-referenced clinical concepts — click any term to see all content where it appears.

Antiepileptic / Analgesic Focal-onset Seizures (adjunct) Off-label: Neuropathic Pain, Fibromyalgia, Anxiety Postherpetic Neuralgia Restless Leg Syndrome (Horizant Formulation)
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