EpilepsyRx

Gabapentin

Neurontin

Seizure aggravation / coverage
May aggravate absence or myoclonic seizures; review syndrome before use (NICE NG217, UK guidance).

DailyMed-verified antiseizure indications

Indication / use

Label / evidence summary
Neurontin: adjunctive treatment of focal-onset seizures, with or without secondary generalization, from age 3 years.
Role
Maintenance
Class
α2δ calcium-channel-subunit ligand; no direct GABA-receptor agonism

Indications checked 26 September 2026. Product, route, age, and treatment-role limits apply. A DailyMed listing alone does not establish FDA approval.

Formulations & strengths

U.S. products unless another country is named. Strengths are per unit or stated volume.

Brand & formulation labels

Each link names the product and formulation it covers. Archived labels do not establish current availability.

Dosing & administration

Adult / product-specific schedule
Focal seizures: 300 mg three times daily is a common initial target; maintenance 900–1,800 mg/day, with up to 3,600 mg/day used in studies.
Pediatric
Age 3–11: start 10–15 mg/kg/day in 3 doses; titrate over about 3 days. Age 3–4 recommended 40 mg/kg/day; age 5–11 recommended 25–35 mg/kg/day. Renal function modifies dosing.
Titration / repeat dosing
Epilepsy, age ≥12 years: start 300 mg three times daily; recommended maintenance is 300–600 mg three times daily. Doses up to 2,400 mg/day were used long term and 3,600 mg/day in a small number for a short duration. The day-1/day-2/day-3 schedule belongs to the postherpetic-neuralgia indication and must not be presented as the labeled epilepsy schedule. Pediatric titration is weight based over approximately 3 days.

Dose adjustment & concentrations

Renal impairment
Adjust dose and interval by creatinine clearance; post-hemodialysis supplemental dosing is specified.
Hepatic impairment
No adjustment expected because gabapentin is not hepatically metabolized.
Serum reference information
2–20 mcg/mL (laboratory reference; clinical correlation is limited)

Safety

Boxed warning
No boxed warning.
Contraindications
Hypersensitivity to gabapentin or ingredients.
Serious precautions & monitoring
Respiratory depression with CNS depressants or underlying respiratory impairment; monitor sedation. DRESS and anaphylaxis/angioedema require prompt assessment. Pediatric behavioral effects and withdrawal-associated seizures are important; taper rather than stop abruptly.

Common / selected adverse effects

  • Somnolence
  • Dizziness
  • Ataxia
  • Fatigue
  • Nystagmus
  • Peripheral edema

Drug interactions: toxicity & clinical action

Partner / combinationClinical effectClinical action
Opioids (including morphine) / other sedativesRespiratory depression and sedation; morphine can also increase gabapentin exposure.Monitor closely, especially with lung disease, older age or renal impairment; adjust doses.
Aluminum/magnesium antacidsReduced absorption.Give gabapentin at least 2 hours after the antacid.

Pregnancy & contraception

Fetal / neonatal risk
Available human gabapentin studies have not indicated an increased risk of major malformations or miscarriage, but have methodological limitations. Prolonged co-exposure with opioids near delivery may increase neonatal withdrawal risk; animal developmental toxicity is reported.
Contraception
Gabapentin did not meaningfully alter norethindrone/ethinylestradiol exposure in the small interaction study described in the label.
Pregnancy / postpartum monitoring
Observe infants after prolonged gabapentin/opioid co-exposure near delivery for withdrawal.

Clinical evidence

Research summaries describe studied populations and outcomes; they do not add indications or constitute treatment recommendations.

Direct pivotal trial

Trial summary

Study design / duration
Randomized, double-blind, placebo-controlled adjunctive focal-seizure trials at fixed daily doses after baseline; responder ratio and ≥50% responder rate were central analyses.
Primary endpoint
No single pivotal endpoint is identified in the cited source.
Results
Pivotal adjunctive focal-seizure trials showed responder ratios favoring gabapentin, with approximately 18–26% median seizure reductions at 900–1,800 mg/day versus little change or worsening with placebo; efficacy increased modestly with dose.

Trial publications

Mechanism of action

  • Binds the α2δ auxiliary subunit of voltage-activated calcium channels; it is not a conventional blocker of the calcium-channel pore.
  • Despite being a GABA analogue, it does not directly activate GABA-A or GABA-B receptors. The label states that the relationship between α2δ binding and therapeutic effects remains incompletely understood.

Pharmacology

Adult values unless specified. Vd/F denotes apparent oral distribution volume.

Pharmacokinetics

Bioavailability
Saturable oral absorption: approximately 60%, 47%, 34%, 33% and 27% at 900, 1,200, 2,400, 3,600 and 4,800 mg/day in three divided doses. These are PK study doses, not dosing recommendations.
Elimination half-life
5–7 hours with normal renal function; markedly prolonged with renal failure.
Volume of distribution
Approximately 58 ± 6 L after a 150 mg IV research dose.
Active metabolite(s)
None: not appreciably metabolized in humans.
Active-metabolite half-life
Not applicable — no clinically established active metabolite.
Protein binding
<3%
Metabolism / elimination
Not appreciably metabolized; excreted unchanged renally

The distribution measurement used an investigational IV dose; this does not imply availability of an IV gabapentin product.

Molecular structure

Molecular structure of Gabapentin
Principal compound; salt and product forms may differ.
NIH PubChem structure and record ↗

Product history

Initial U.S. approval
1993
Brands
Neurontin
Manufacturer / marketer
Viatris/Pfizer legacy brand (Neurontin)
Generic availability
Yes
Related drugs
Structural GABA analogue but does not act at GABA receptors; closely related to pregabalin through α2δ binding.

Sources & review status

Representative sources are selected product labels, not an exhaustive list of generic manufacturers. Consult the exact product and formulation prescribed. Brand-name package inserts are linked separately.

Brand reference: Neurontin capsules / tablets / solution ↗

Indications and DailyMed PDFs checked: 2026-09-26. Other profile sources reviewed: 2026-09-15 · label revision noted at that review: 4/2025. This is a draft reference; final review is pending.

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