Neurontin (gabapentin) is an anticonvulsant and neuropathic pain agent indicated for the management of postherpetic neuralgia and as adjunctive therapy in the treatment of partial onset seizures with and without secondary generalization in patients 3 years of age and older. Its mechanism of action, while not fully elucidated, is distinct from other antiepileptic drugs, involving binding to the α2δ subunit of voltage-gated calcium channels in the central nervous system. This action is believed to modulate the release of several neurotransmitters, contributing to its efficacy in stabilizing neuronal activity and reducing aberrant pain signaling. Available in multiple formulations including capsules, tablets, and oral solution, it offers flexible dosing to meet individual patient needs within a structured therapeutic regimen.

Features

• Active pharmaceutical ingredient: Gabapentin
• Available strengths: 100 mg, 300 mg, 400 mg capsules; 600 mg, 800 mg film-coated tablets; 250 mg/5 mL oral solution
• Mechanism: Binds to the α2δ subunit of voltage-dependent calcium channels
• Pharmacokinetics: Nonlinear absorption; bioavailability decreases with increasing dose
• Half-life: 5–7 hours in patients with normal renal function
• Excretion: Primarily renal, unchanged
• Formulation options allow for dose titration and administration flexibility

Benefits

• Provides significant reduction in neuropathic pain scores, particularly in postherpetic neuralgia
• Effective adjunctive therapy for reducing seizure frequency in partial onset epilepsies
• Generally favorable side effect profile compared to older generation anticonvulsants
• No known pharmacokinetic interactions with hepatic enzyme-inducing or inhibiting agents
• Multiple formulation types support individualized dosing strategies
• May improve sleep quality and overall quality of life in chronic pain conditions

Common use

Neurontin is primarily prescribed for two FDA-approved indications: management of postherpetic neuralgia (PHN) and adjunctive treatment of partial seizures. In clinical practice, it is also used off-label for various neuropathic pain conditions including diabetic neuropathy, fibromyalgia, and neuropathic pain associated with spinal cord injury. Its use in migraine prophylaxis and restless legs syndrome is also documented in clinical guidelines, though these represent off-label applications. The dosing regimen varies significantly between indications, with neuropathic pain typically requiring lower doses than seizure management. Treatment should always be initiated at the lowest effective dose and titrated gradually based on clinical response and tolerability.

Dosage and direction

For postherpetic neuralgia: Therapy should be initiated with a single 300 mg dose on Day 1, 600 mg/day (300 mg two times daily) on Day 2, and 900 mg/day (300 mg three times daily) on Day 3. The dose may be increased as needed for pain relief up to 1800 mg/day (600 mg three times daily). Doses up to 3600 mg/day have been studied but did not demonstrate additional benefit.

For epilepsy: Patients 12 years and older: initial dose of 300 mg three times daily; may be increased to 300–600 mg three times daily. The maximum dose is 2400–3600 mg/day divided three times daily. Pediatric dosing (3–12 years) is weight-based: initial dose of 10–15 mg/kg/day in three divided doses, titrated over three days to effective dose.

Administration should occur with or without food, though high-fat meals may increase absorption. Tablets should be swallowed whole; capsules may be opened and contents mixed with food or liquid if swallowing difficulty exists. Dosage adjustment is required in renal impairment based on creatinine clearance.

Precautions

Patients should be cautioned about the potential for dizziness, somnolence, and other CNS effects, particularly during the titration phase. Activities requiring mental alertness (e.g., operating machinery, driving) should be avoided until the individual response is established. Abrupt discontinuation may precipitate withdrawal symptoms including anxiety, insomnia, nausea, pain, and sweating; taper gradually over at least one week. Increased seizure risk may occur upon abrupt withdrawal. Suicidal ideation and behavior have been reported with antiepileptic drugs; patients should be monitored for emergence or worsening of depression, suicidal thoughts, or unusual changes in mood or behavior. Peripheral edema may occur, particularly in elderly patients or those with cardiac conditions. Patients with a history of drug abuse should be monitored closely, as gabapentin has potential for misuse.

Contraindications

Hypersensitivity to gabapentin or any component of the formulation. No other absolute contraindications exist, though extreme caution is warranted in patients with severe renal impairment (creatinine clearance <30 mL/min) without appropriate dosage adjustment. The oral solution contains potassium acesulfame, which is contraindicated in patients with phenylketonuria.

Possible side effect

Most common adverse reactions (≥5% and twice placebo) in neuropathic pain: dizziness (28%), somnolence (21%), peripheral edema (8%), asthenia (6%), diarrhea (6%), dry mouth (5%), constipation (4%), amblyopia (blurred vision) (4%). In epilepsy studies: somnolence (19%), dizziness (17%), ataxia (13%), fatigue (11%), nystagmus (8%), tremor (7%), diplopia (6%), peripheral edema (3%), weight increase (2%). Serious but rare adverse effects include angioedema, hypersensitivity reactions, Stevens-Johnson syndrome, and drug reaction with eosinophilia and systemic symptoms (DRESS). Hematologic effects including leukopenia and thrombocytopenia have been reported.

Drug interaction

No clinically significant pharmacokinetic interactions with phenytoin, carbamazepine, valproic acid, or oral contraisceptives. Antacids containing aluminum and magnesium reduce gabapentin bioavailability by approximately 20%; administer gabapentin at least 2 hours following antacid. Additive CNS depression may occur with alcohol, opioids, benzodiazepines, and other sedating medications. Morphine co-administration increases gabapentin exposure; monitor for increased gabapentin effects. Hydrocodone combination may enhance CNS depression.

Missed dose

If a dose is missed, it should be taken as soon as remembered unless it is almost time for the next scheduled dose. In that case, skip the missed dose and resume the regular dosing schedule. Do not double the dose to make up for a missed administration. Consistent timing is important for maintaining stable plasma concentrations, particularly for seizure control.

Overdose

Symptoms may include dizziness, double vision, slurred speech, drowsiness, lethargy, and diarrhea. Significant overdose may result in hypotension, respiratory depression, and coma. Fatalities have been reported at doses between 4900 mg and 60,000 mg. Management is supportive and symptomatic, including airway protection and hemodynamic support. Hemodialysis may be beneficial due to gabapentin’s primarily renal elimination (removes approximately 35% of dose over 3 hours). There is no specific antidote.

Storage

Store at 25°C (77°F); excursions permitted to 15–30°C (59–86°F). Keep in original container with lid tightly closed to protect from moisture. Oral solution should be stored in original bottle at room temperature; discard any unused portion after 56 days of first opening. Keep all medications out of reach of children and pets.

Disclaimer

This information is for educational purposes only and does not constitute medical advice. Always consult with a qualified healthcare professional before starting, changing, or stopping any medication. Dosage and indications may vary based on individual patient factors. Only a healthcare provider can determine the appropriate treatment based on medical history, current condition, and other factors.

Reviews

Clinical trials demonstrate Neurontin’s efficacy in reducing pain scores by ≥50% in approximately 30% of PHN patients versus 10% with placebo. In epilepsy studies, responder rates (≥50% seizure reduction) ranged from 16–28% versus 10% with placebo. Real-world evidence supports its effectiveness, though individual responses vary considerably. Many patients report significant improvement in quality of life measures, particularly regarding sleep disturbance and functional capacity. Common complaints in patient reviews include drowsiness, cognitive fog, and weight gain, though these often diminish with continued use or dose adjustment. Overall satisfaction is moderate to high among responders, with discontinuation rates primarily due to side effects rather than lack of efficacy.