Neurontin (Gabapentin) Facts

• Generic name: Gabapentin
• Brand/Trade names: Neurontin
• Dosages: Tablets 600 mg, 800 mg; Capsules 100 mg, 300 mg, 400 mg; Oral solution 250 mg per 5 mL
• Pharmacologic category: Anticonvulsant
• FDA approved: December 30, 1993
• Manufacturer: Pfizer
• Habit forming? No
• Pregnancy risk factor: C

Neurontin (gabapentin) is an antiepileptic drug (AED) with analgesic properties. It is approved by the Food and Drug Administration for adjunctive treatment of partial epilepsy and management of postherpetic neuralgia. It may be considered in a number of psychiatric, neurologic, and pain disorders.

Gabapentin most common side effects in adult patients include dizziness, drowsiness, fatigue, and peripheral edema (swelling of extremities) 13.

• Absorption: Bioavailability decreases as dose increases: bioavailability is approximately 60%, 47%, 34%, 33%, and 27% following 900, 1,200, 2,400, 3,600, and 4,800 mg/day given in 3 divided doses, respectively. Food has only a slight effect on rate and extent of absorption.
• Metabolism: Gabapentin is not appreciably metabolized in humans.
• Elimination half-life: 5-7 hours.
• Excretion: excreted unchanged in the kidney.

• small number of drug interactions
• lack of liver and enzyme-inducing or inhibiting effects
• low toxicity
• effective in some people with bipolar mood disorders that have not responded to lithium or other mood-stabilizers
• generic availability

• short half-life which requires a three times daily regimen
• not as efficacious as other anticonvulsants 14
• sedating side effects 13

• Painful diabetic neuropathy 5
• Migraine prophylaxis 3
• Interstitial cystitis 4
• Hot flashes
• Partial seizures, monotherapy
• Essential tremor 6
• Bipolar disorder 11
• Phantom limb syndrome
• Restless leg syndrome 7
• Postoperative pain management 2, 15
• Posttraumatic stress disorder (PTSD) 8
• Alcohol withdrawal 9
• Chronic daily headache 12

Neurontin for Bipolar disorder
Neurontin may have a role as adjunctive agent in the treatment of patients with bipolar disorders particularly when complicated by co-morbid anxiety disorder or substance abuse. Randomized clinical trial comparing the prophylactic efficacy of adjunctive gabapentin to placebo suggests that, despite lack of acute efficacy, treatment with gabapentin might provide some benefit on the long-term outcome of bipolar disorder 11. Neurontin is usually very well tolerated and has no pharmacological interference with other mood stabilisers. However, in the placebo-controlled study Neurontin has not been found to be an effective adjunctive treatment for bipolar disorder 10. This drug failing to show clear antimanic efficacy in randomized trials.

Dose ranges of Neurontin used in bipolar disorder have ranged from 600 mg to 1200 mg per day, with a low starting dose titrated up over a few days.

Neurontin for pain management
Neurontin is efficacious treatments for neuropathic and postsurgical pain.

Neuropathic pain
Multiple, large, high-quality studies have demonstrated the safety and efficacy of gabapentin in neuropathic pain. Gabapentin reduces pain and improves sleep. Sedation, dizziness and ataxia are most common most effects.

Acute, post-operative pain
Gabapentin may have a place in the treatment of postoperative pain 2, 15. Accumulating evidence indicates that gabapentin exert important effects following surgery. High-quality studies have demonstrated analgesic and opioid-sparing efficacy with gabapentin following various surgical procedures. Gabapentin reduces movement-evoked pain and this can lead to enhanced functional postoperative recovery. Reduction of opioid consumption allows to reduce opioid-related side effects, such as nausea, vomiting, and urinary retention.

Gabapentin is structurally related to GABA. However, it does not bind to GABAA or GABAB receptors, and it does not appear to influence synthesis or uptake of GABA. High affinity gabapentin binding sites have been located throughout the brain; these sites correspond to the presence of voltage-gated calcium channels specifically possessing the alpha-2-delta-1 subunit. This channel appears to be located presynaptically, and may modulate the release of excitatory neurotransmitters which participate in epileptogenesis and nociception.

Neurontin (gabapentin) should be tapered off gradually. Tapering Neurontin should be considered even in patients without epilepsy, since abrupt discontinuation has been associated with seizures and development of a syndrome resembling alcohol or benzodiazepine withdrawal. Neurontin should be suddenly discontinued only when necessary because of a serious side effects.

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• 1. U.S. Food and Drug Administration. Neurontin (Gabapentin) U.S. Prescribing Information. Available at (PDF format): Prescribing Information
• 2. Ho KY, Gan TJ, Habib AS. Gabapentin and postoperative pain--a systematic review of randomized controlled trials. Pain. 2006 Dec 15;126(1-3):91-101. PubMed
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