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Neurontin

Pronunciation

Generic Name: Gabapentin
Class: Anticonvulsants, Miscellaneous
VA Class: CN400
Chemical Name: 1-(Aminomethyl)-cyclohexaneacetic acid
Molecular Formula: C9H17NO2C16H27NO6
CAS Number: 60142-96-3

Introduction

Anticonvulsant; structurally related to the inhibitory CNS neurotransmitter GABA; also possesses analgesic activity.1 4 6 7 8 9 60 61 Gabapentin enacarbil is a prodrug of gabapentin.61 76 83

Uses for Neurontin

Seizure Disorders

Gabapentin (as conventional [immediate-release] preparations) is used in combination with other anticonvulsant agents for the management of partial seizures with or without secondary generalization in adults and children ≥3 years of age.1 2 8 9

Safety and efficacy of gabapentin gastroretentive tablets (Gralise) and gabapentin enacarbil extended-release tablets (Horizant) not established in patients with seizure disorders.60 61

Neuropathic Pain

Gabapentin (as conventional [immediate-release] preparations or gastroretentive tablets) and gabapentin enacarbil are used for management of postherpetic neuralgia (PHN) in adults.1 20 21 22 23 24 38 39 40 60 61 62 70

Gabapentin is considered one of several first-line therapies for PHN.66 67

Gabapentin also has been used for management of pain associated with diabetic neuropathy.20 21 22 23 24 25 40 41 42 43 44 45 70

Gabapentin also has demonstrated some evidence of benefit for the relief of chronic neurogenic pain in a variety of conditions including trigeminal neuralgia,20 21 46 47 pain and control of paroxysmal symptoms of multiple sclerosis (MS),20 21 48 49 complex regional pain syndromes,20 52 53 HIV-related peripheral neuropathy,20 21 50 and neuropathic pain associated with cancer.20 21 51 Additional study needed to further elucidate precise role in the management of these conditions.20 21 23

Restless Legs Syndrome

Gabapentin enacarbil is used for symptomatic treatment of moderate-to-severe primary restless legs syndrome (Ekbom syndrome) in adults.61 71 74 78 79 80 81 82 Not recommended in patients who are required to sleep during the daytime and remain awake at night.61

Gabapentin also has been used for management of restless legs syndrome; however, the drug currently is not labeled by FDA for this use.26 27 28 71 72 73 78 81 82

Vasomotor Symptoms

Gabapentin has been used for the management of vasomotor symptoms (e.g., hot flashes) in women with breast cancer.30

Gabapentin has been used for the management of vasomotor symptoms (e.g., hot flashes) associated with menopause.31 34 54

Neurontin Dosage and Administration

General

  • Closely monitor for notable changes in behavior that could indicate the emergence or worsening of suicidal thoughts or behavior or depression.55 56 57 59 60 61 (See Suicidality Risk under Cautions.)

  • If therapy is discontinued, gradually decrease dosage to avoid manifestations of abrupt withdrawal.1 60 61 (See Dosage under Dosage and Administration, and also see Withdrawal Seizures under Cautions.)

Administration

Oral Administration

Formulation Considerations

Gabapentin: Commercially available as conventional (immediate-release) capsules, tablets, or oral solution.1 Also available as gastroretentive tablets (Gralise); although not considered by FDA to be an extended-release formulation, the gastroretentive tablets are sometimes referred to in this manner because of similar pharmacokinetics to an extended-release dosage form.60 62 63 64 65 Because of differences in pharmacokinetics that affect frequency of administration, gabapentin gastroretentive tablets are not interchangeable with other gabapentin preparations.60 (See Pharmacokinetics.)

Gabapentin enacarbil: Commercially available as extended-release tablets (Horizant).61 Because of differences in pharmacokinetics that affect frequency of administration, gabapentin enacarbil extended-release tablets are not interchangeable with other gabapentin preparations.61 (See Pharmacokinetics.)

Gabapentin Conventional (Immediate-release) Tablets, Capsules, or Oral Solution

Administer orally 3 times daily without regard to meals.1 Interval between doses should not exceed 12 hours.1

If film-coated scored tablets containing 600 or 800 mg of gabapentin are divided to administer a 300- or 400-mg dose, use the remaining half tablet for the next dose.1 Discard half tablets that are not used within 28 days.1

Swallow capsules whole with water.1

Gabapentin Gastroretentive Tablets (Gralise)

Administer orally once daily with the evening meal.60 Swallow tablets whole; do not chew, crush, or split.60

Gabapentin Enacarbil Extended-release Tablets (Horizant)

Administer orally once or twice daily depending on indication.61

When used for restless legs syndrome, administer once daily at about 5 p.m.; if a dose is missed, take next dose the following day as scheduled.61

When used for PHN, administer orally twice daily; if a dose is missed, skip dose and take next dose at regularly scheduled time.61

Swallow tablets whole; do not crush, chew, or cut.61

Dosage

Pediatric Patients

Seizure Disorders
Partial Seizures
Oral

Gabapentin conventional (immediate-release) tablets, capsules, or oral solution in children 3–11 years of age: Initially, 10–15 mg/kg daily in 3 divided doses.1 Interval between doses should not exceed 12 hours.1 Titrate upward over a period of approximately 3 days until an effective maintenance dosage is achieved.1 Recommended maintenance dosage in children 3–4 years of age is 40 mg/kg daily in 3 divided doses; recommended maintenance dosage in children 5–11 years of age is 25–35 mg/kg daily in 3 divided doses.1 Dosages up to 50 mg/kg daily have been well tolerated in clinical studies.1

Gabapentin conventional (immediate-release) tablets, capsules, or oral solution in children ≥12 years of age: Initially, 300 mg 3 times daily.1 Maintenance dosage of 300–600 mg 3 times daily recommended.1 Interval between doses should not exceed 12 hours.1 Dosages up to 2.4 g daily have been well tolerated in long-term clinical studies, and a small number of patients have tolerated dosages of 3.6 g daily for short periods.1

If therapy is discontinued, dosage reduced, or an alternative drug substituted, such changes should be done gradually over ≥1 week.1

Adults

Seizure Disorders
Partial Seizures
Oral

Gabapentin conventional (immediate-release) tablets, capsules, or oral solution: Initially, 300 mg 3 times daily.1 Maintenance dosage of 300–600 mg 3 times daily recommended.1 Interval between doses should not exceed 12 hours.1 Dosages up to 2.4 g daily have been well tolerated in long-term clinical studies, and a small number of patients have tolerated dosages of 3.6 g daily for short periods.1

If therapy is discontinued, dosage reduced, or an alternative drug substituted, such changes should be done gradually over ≥1 week.1

Neuropathic Pain
Postherpetic Neuralgia
Oral

Gabapentin conventional (immediate-release) tablets, capsules, or oral solution: 300 mg on day 1, 300 mg twice daily on day 2, and 300 mg 3 times daily on day 3.1 Increase dosage as needed for relief of pain up to a total dosage of 1.8 g daily in 3 divided doses.1 No evidence of additional benefit with dosages >1.8 g daily.1 If therapy is discontinued, dosage reduced, or an alternative drug substituted, such changes should be done gradually over ≥1 week.1

Gabapentin gastroretentive tablets (Gralise): Titrate gradually over 2 weeks up to recommended maintenance dosage of 1.8 g once daily as follows: 300 mg once daily on day 1, 600 mg once daily on day 2, 900 mg once daily on days 3–6, 1.2 g once daily on days 7–10, 1.5 g once daily on days 11–14, and 1.8 g once daily on day 15.60 If therapy is discontinued, dosage reduced, or an alternative drug substituted, such changes should be done gradually over ≥1 week.60

Gabapentin enacarbil extended-release tablets (Horizant): Initially, 600 mg once daily in the morning for 3 days, then increase to recommended maintenance dosage of 600 mg twice daily.61 Dosages >1.2 g daily provide no additional benefit and associated with an increased incidence of adverse effects.61 When discontinuing therapy in patients receiving a dosage of 600 mg twice daily, reduce to 600 mg once daily for 1 week prior to withdrawing therapy.61

Diabetic Neuropathy
Oral

Dosages of gabapentin 900 mg to 3.6 g daily have been used; however, pain relief generally observed in patients receiving dosages >1.8 g daily.24 25

Restless Legs Syndrome
Oral

Gabapentin enacarbil extended-release tablets (Horizant): 600 mg once daily at approximately 5 p.m.61

When discontinuing therapy, gradual withdrawal only necessary in patients receiving higher than recommended dosages; in such cases, reduce dosage to 600 mg once daily for 1 week prior to withdrawing therapy.61

Vasomotor Symptoms
Oral

300 mg 3 times daily as gabapentin conventional (immediate-release) preparations has been effective; higher dosages may provide additional benefit.30 31 37

Special Populations

Renal Impairment

Adjust dosage of gabapentin or gabapentin enacarbil in patients with renal impairment based on Clcr (see Tables 1–4).1 60 61

Table 1. Dosage Adjustments for Renal Impairment in Adults and Children ≥12 Years of Age Receiving Conventional (Immediate-release) Gabapentin 1

Clcr (mL/minute)

Adjusted Dosage Regimen

>30 to 59

200–700 mg twice daily (i.e., up to a total dosage of 1.4 g daily)

>15 to 29

200–700 mg once daily

15

100–300 mg once daily

<15

Reduce dosage in proportion to Clcr (e.g., a patient with a Clcr of 7.5 mL/minute should receive one-half the dosage that a patient with a Clcr of 15 mL/minute should receive)

Patients undergoing hemodialysis

In addition to the renally adjusted maintenance dosage, administer supplemental dose of 125–350 mg following each 4-hour hemodialysis session

Table 2. Dosage Adjustments for Renal Impairment in Adults Receiving Gabapentin Gastroretentive Tablets60

Clcr (mL/minute)

Adjusted Dosage Regimen

30–60

600 mg to 1.8 g once daily; initiate at 300 mg once daily and may titrate according to same schedule recommended for those with normal renal function based on individual patient response and tolerability

<30

Do not use

Patients undergoing hemodialysis

Do not use

Table 3. Dosage Adjustments for Renal Impairment in Adults Receiving Gabapentin Enacarbil for PHN61

Clcr (mL/minute)

Titration Schedule

Maintenance Dosage

Tapering Schedule

30–59

300 mg once daily in the morning for 3 days

300 mg twice daily; increase to 600 mg twice daily as necessary based on patient response and tolerability

Reduce frequency of maintenance dosage to once daily in the morning for 1 week

15–29

300 mg once daily in the morning on days 1 and 3

300 mg once daily in the morning; increase to 300 mg twice daily if necessary based on patient response and tolerability

In patients currently receiving a maintenance dosage of 300 mg twice daily, reduce to 300 mg once daily in the morning for 1 week; in patients currently receiving a maintenance dosage of 300 mg once daily, no taper needed

<15 not on hemodialysis

None

300 mg every other day in the morning; increase to 300 mg once daily if necessary based on patient response and tolerability

None

<15 on hemodialysis

None

300 mg following each hemodialysis session; increase to 600 mg if necessary based on patient response and tolerability

None

Table 4. Dosage Adjustments for Renal Impairment in Adults Receiving Gabapentin Enacarbil for Restless Legs Syndrome61

Clcr (mL/minute)

Target Dosage

30–59

Initiate at 300 mg once daily, then increase to 600 mg once daily as needed

15–29

300 mg once daily

<15 not on hemodialysis

300 mg every other day

<15 on hemodialysis

Use not recommended

Geriatric Patients

Select dosage carefully, usually initiating therapy at the low end of the dosage range.1 Adjust dosage based on Clcr.1 (See Renal Impairment under Dosage and Administration.)

Cautions for Neurontin

Contraindications

  • Gabapentin: Known hypersensitivity to gabapentin or any ingredient in the formulation.1 60

  • Gabapentin enacarbil: Manufacturer states none known.61

Warnings/Precautions

Warnings

Suicidality Risk

Increased risk of suicidality (suicidal ideation or behavior) observed in an analysis of studies using various anticonvulsants in patients with epilepsy, psychiatric disorders (e.g., bipolar disorder, depression, anxiety), and other conditions (e.g., migraine, neuropathic pain); risk in patients receiving anticonvulsants (0.43%) was approximately twice that in patients receiving placebo (0.24%).1 55 56 57 60 61 Increased suicidality risk was observed ≥1 week after initiation of anticonvulsant therapy and continued through 24 weeks.1 55 56 57 60 61 Risk was higher for patients with epilepsy compared with those receiving anticonvulsants for other conditions.1 55 56 57 60 61

Closely monitor all patients currently receiving or beginning anticonvulsant therapy for changes in behavior that may indicate emergence or worsening of suicidal thoughts or behavior or depression.55 56 57 Anxiety, agitation, hostility, hypomania, and mania may be precursors to emerging suicidality.55

Balance risk of suicidality with the risk of untreated illness.55 Epilepsy and other illnesses treated with anticonvulsants are themselves associated with morbidity and mortality and an increased risk of suicidality.1 60 61 If suicidal thoughts or behavior emerge during anticonvulsant therapy, consider whether these symptoms may be related to the illness itself.1 60 61 (See Advice to Patients.)

Cognitive/Neuropsychiatric Effects

Emotional lability (primarily behavioral problems), hostility (including aggressive behaviors), thought disorders (including concentration and school performance changes), and hyperkinesia (primarily restlessness and hyperactivity) associated with use in children 3–12 years of age with epilepsy.1

Dizziness and Somnolence

Risk of somnolence, sedation, and dizziness.1 60 61 (See Advice to Patients.) Avoid concomitant use of alcohol or other drugs that can potentiate these effects.1 60 61 (See Specific Drugs under Interactions.)

Effects on Driving and Operating Heavy Machinery

Risk of substantial driving impairment; may be related to somnolence or other CNS effects of the drug.1 61 72 (See Dizziness and Somnolence under Cautions.) Duration of such impairment not known.1 61

Patients should not drive (or operate other complex machinery) until they have gained sufficient experience with the drug.1 61

Withdrawal Seizures

Abrupt withdrawal may result in increased seizure frequency and other withdrawal symptoms (e.g., anxiety, insomnia, nausea, pain); withdraw therapy gradually.1 60 61 (See Dosage under Dosage and Administration.)

Tumorigenic Potential

Increased incidence of pancreatic acinar adenocarcinomas observed in rat carcinogenicity studies with gabapentin and gabapentin enacarbil.1 61 Clinical relevance of these findings to humans unknown.1 60 61 72

New tumors or worsening of preexisting tumors reported in some patients receiving gabapentin; however, causal relationship not established.60 61

Sudden, Unexplained Deaths in Epilepsy

Higher incidence of sudden and unexplained deaths than would be expected in a healthy (nonepileptic) population; however, incidence is within range of estimates for patients with epilepsy or refractory epilepsy.1

Lack of Interchangeability

Different formulations of gabapentin (e.g., conventional [immediate-release] gabapentin preparations, gabapentin gastroretentive tablets, gabapentin enacarbil extended-release tablets) not interchangeable because of differences in pharmacokinetics that affect frequency of administration.60 61

Sensitivity Reactions

Multiorgan Hypersensitivity Reactions

Multiorgan hypersensitivity reactions (also known as drug reaction with eosinophilia and systemic symptoms or DRESS) reported with anticonvulsants, including gabapentin; clinical presentation is variable but typically includes fever, rash, eosinophilia, and/or lymphadenopathy associated with other organ system involvement (e.g., hepatitis, nephritis, hematologic abnormalities, myositis, myocarditis).1 60 61 Potentially fatal or life-threatening.1 60 61

If manifestations of DRESS occur, evaluate patient immediately; discontinue gabapentin if an alternative etiology cannot be identified.1 60 61

Specific Populations

Pregnancy

Category C.1

No adequate and well-controlled studies to date in pregnant women; developmental toxicity (e.g., skeletal abnormalities, hydroureter and hydronephrosis, increased embryofetal mortality) demonstrated in animals.1 16 60

North American Antiepileptic Drug (NAAED) Pregnancy Registry at 888-233-2334 (for patients); NAAED registry information also available on the website .1

Lactation

Distributed into milk; use only if potential benefits outweigh risks.1 60 The manufacturer of gabapentin enacarbil states to discontinue nursing or the drug.61

Pediatric Use

Safety and efficacy of conventional (immediate-release) gabapentin as adjunctive therapy for management of partial seizures not established in children <3 years of age.1

Safety and efficacy of conventional (immediate-release) gabapentin for management of PHN not established in children.1

Safety and efficacy of gabapentin gastroretentive tablets not established in children.60

Safety and efficacy of gabapentin enacarbil not established in children.61

Geriatric Use

Insufficient experience with conventional (immediate-release) gabapentin for the management of partial seizures in patients ≥65 years of age to determine whether they respond differently than younger adults.1 Select dosage carefully.1 (See Geriatric Patients under Dosage and Administration.)

Appeared to be more effective for the management of PHN in patients >75 years of age than in younger patients; apparent difference in efficacy may be related to decreased renal function in older patients.1 Adverse effects in older patients with PHN generally similar to those in younger adults; however, the incidence of peripheral edema and ataxia appears to increase with age.1

Adverse effects reported with gabapentin as gastroretentive tablets generally similar across all age groups except for peripheral edema, which tended to increase with age.60

Insufficient experience with gabapentin enacarbil in patients ≥65 years of age to determine whether they respond differently than younger patients.61 No overall differences in safety and efficacy observed between geriatric and younger patients receiving the drug.61

Geriatric patients may have decreased hepatic, renal, or cardiac function, with increased risk of adverse effects.1 16 60 61 Use with caution; dosage reductions may be necessary in those with renal impairment.1 (See Renal Impairment under Dosage and Administration.)

Renal Impairment

Eliminated renally; dosage adjustments may be necessary in patients with renal impairment.1 60 61 (See Renal Impairment under Dosage and Administration.)

Common Adverse Effects

Children 3–12 years of age receiving conventional (immediate-release) gabapentin as adjunctive therapy for partial seizures: viral infection, fever, nausea and/or vomiting, somnolence, hostility.1

Adults and children >12 years of age receiving conventional (immediate-release) gabapentin as adjunctive therapy for partial seizures: somnolence, dizziness, ataxia, fatigue, nystagmus.1

Adults receiving conventional (immediate-release) gabapentin for management of PHN: dizziness, somnolence, peripheral edema.1

Adults receiving gabapentin gastroretentive tablets for PHN: dizziness.60

Adults receiving gabapentin enacarbil for PHN: dizziness, somnolence, headache.61

Adults receiving gabapentin enacarbil for restless legs syndrome: somnolence/sedation, dizziness.61

Interactions for Neurontin

Not metabolized by CYP isoenzymes.1 Does not inhibit CYP isoenzymes 1A2, 2C9, 2C19, 2D6, 2E1, or 3A4 in vitro; causes slight inhibition of CYP2A6 at high concentrations.1

Specific Drugs

Drug

Interaction

Comments

Alcohol

Increases risk of sedation/somnolence, dizziness1 60 61

Causes rapid release of drug from gabapentin enacarbil extended-release tablets61

Avoid concomitant use1 60 61

Antacids

Reduced bioavailability of gabapentin, but to a smaller extent when gabapentin administered 2 hours after antacid1 60

Administer gabapentin at least 2 hours after antacid1 60

Anticonvulsants

Plasma concentrations of carbamazepine, phenytoin, valproic acid, phenobarbital, and diazepam in existing treatment regimens not affected by gabapentin;1 3 12 13 14 60 pharmacokinetics of gabapentin not affected by these drugs1 6 12 15 60

May be used concomitantly without concern about alterations in plasma concentrations of gabapentin or other anticonvulsant drugs1

Cimetidine

Possible decrease in gabapentin clearance 1 60

Not likely to be clinically important1 60

Naproxen

Increased bioavailability of gabapentin at subtherapeutic dosages of both drugs1 60

Extent of interaction at usual therapeutic dosages is unknown1 60

Opiate analgesics (e.g., hydrocodone, morphine)

Possible increased gabapentin concentrations and increased risk of adverse effects (e.g., somnolence, dizziness, nausea) 1

Hydrocodone: Possible decrease in plasma concentrations of hydrocodone1 60

Morphine: Morphine pharmacokinetics based on a controlled-release preparation not affected by gabapentin (when administered 2 hours after the morphine dose)1

Carefully observe for signs of CNS or respiratory depression and reduce dosage of gabapentin or the opiate analgesic if indicated1

Oral contraceptives

Possible increase in peak plasma concentrations of norethindrone1

Not likely to be clinically important1 60

Probenecid

No pharmacokinetic interaction observed1

Neurontin Pharmacokinetics

Absorption

Bioavailability

Conventional (immediate-release) gabapentin: Following oral administration, absorbed principally in the proximal small intestine via a saturable L-amino acid transport system; bioavailability is not dose proportional and decreases as dose increases.1 60 63 83 84 Bioavailability is 60 to 27% for doses ranging from 900 mg to 4.8 g daily.1

Gabapentin gastroretentive tablets: In healthy individuals, time to peak plasma concentrations is prolonged (about 4–6 hours longer), peak plasma concentrations are higher, and systemic exposure is lower relative to immediate-release formulations.60

Gabapentin enacarbil extended-release tablets: Absorbed by high-capacity transporters throughout the GI tract and not affected by saturable absorption; this improves bioavailability and allows for dose-proportional exposure.61 72 74 78 80 83 Mean bioavailability in the fed state is about 75% and in the fasted state is about 42–65%.61 Steady-state achieved in about 2 days with daily administration.61

Food

Conventional (immediate-release) gabapentin: Food does not substantially affect bioavailability.1 60 64

Gabapentin gastroretentive tablets: Food increases absorption of the drug formulation; tablets swell upon contact with gastric fluid to a size that promotes gastric retention for approximately 8–10 hours when taken with a meal.60 63 64 65

Gabapentin enacarbil extended-release tablets: Food increases systemic exposure.61 76

Distribution

Extent

Readily crosses the blood-brain barrier and concentrates in brain tissue.29 Distributed into breast milk.1 Not known whether gabapentin crosses the placenta.1

Plasma Protein Binding

<3%.1

Elimination

Metabolism

Gabapentin is not appreciably metabolized.1 61

Gabapentin enacarbil, the prodrug of gabapentin, is rapidly and efficiently converted to gabapentin by first-pass hydrolysis following oral administration.61 74

Elimination Route

Excreted renally as unchanged drug.1 61

Half-life

Approximately 5–7 hours.1 60 61

Special Populations

In children <5 years of age, clearance normalized for weight is higher than in adults and children ≥5 years of age.1

In patients with renal impairment, plasma clearance is decreased and half-life is prolonged.1 In patients with Clcr <30 mL/minute, half-life of 52 hours reported with conventional (immediate-release) gabapentin; in anuric patients, half-life reported to be 132 hours on nondialysis days and 3.8 hours during hemodialysis.1

Stability

Storage

Oral

Gabapentin Conventional (immediate-release) Capsules and Tablets

25°C (may be exposed to 15–30°C).1

Gabapentin Conventional (immediate-release) Oral Solution

2–8°C.1

Gabapentin Gastroretentive Tablets (Gralise)

25°C (may be exposed to 15–30°C).60

Gabapentin Enacarbil Extended-release Tablets (Horizant)

25°C (may be exposed to 15–30°C).61

Actions

  • Mechanism of anticonvulsant action is unknown.1 4 5 7 8 9 Does not bind to GABA receptors,1 4 5 6 7 17 affect GABA reuptake or metabolism, 1 6 7 17 or act as a precursor of GABA or other substances active at GABA receptors.1 17

  • Mechanism of analgesic action is unknown.1 20 21 22 23 Prevents allodynia (pain-related behavior in response to normally innocuous stimuli) and hyperalgesia (exaggerated response to painful stimuli) in several animal models of neuropathic pain.1 20 Decreases pain-related responses after peripheral inflammation in animals; however, has not altered immediate pain-related behaviors, and clinical relevance is not known.1 In vitro studies demonstrate that the drug binds with high affinity to the α2δ subunit of voltage-activated calcium channels; however, clinical relevance not known.1 66 69

Advice to Patients

  • Importance of advising patient to read the manufacturer’s medication guide before initiating therapy and each time the prescription is refilled.1

  • Importance of taking gabapentin exactly as prescribed.1 Importance of not abruptly discontinuing therapy.1

  • Risk of suicidality.1 55 56 57 59 Importance of patients, family, and caregivers being alert to day-to-day changes in mood, behavior, and actions and immediately informing clinician of any new or worrisome behaviors (e.g., talking or thinking about wanting to hurt oneself or end one’s life, withdrawing from friends and family, becoming depressed or experiencing worsening of existing depression, becoming preoccupied with death and dying, giving away prized possessions).1 55

  • Potential for drug to impair mental alertness or physical coordination; avoid driving or operating machinery until effects on individual are known.1

  • Risk of serious hypersensitivity reactions affecting multiple organ systems (e.g., liver, kidney).1 Importance of informing patients to contact their clinician immediately if a rash or other manifestations of hypersensitivity (e.g., fever, lymphadenopathy) occur.1

  • Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.1

  • Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs.1

  • Importance of informing patients of other important precautionary information.1 (See Cautions.)

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

Gabapentin

Routes

Dosage Forms

Strengths

Brand Names

Manufacturer

Oral

Capsules

100 mg*

Gabapentin Capsules

Neurontin

Pfizer

300 mg*

Gabapentin Capsules

Neurontin

Pfizer

400 mg*

Gabapentin Capsules

Neurontin

Pfizer

Solution

250 mg/5 mL*

Neurontin

Pfizer

Tablets

100 mg*

Gabapentin Tablets

300 mg*

Gabapentin Tablets

Gralise

Depomed

400 mg*

Gabapentin Tablets

600 mg*

Gabapentin Tablets

Gralise

Depomed

800 mg*

Gabapentin Tablets

Tablets, film-coated

600 mg*

Gabapentin Tablets

Neurontin

Pfizer

800 mg*

Gabapentin Tablets

Neurontin

Pfizer

Gabapentin Enacarbil

Routes

Dosage Forms

Strengths

Brand Names

Manufacturer

Oral

Tablets, extended-release

300 mg

Horizant

XenoPort

600 mg

Horizant

XenoPort

AHFS DI Essentials. © Copyright, 2004-2016, Selected Revisions November 23, 2015. American Society of Health-System Pharmacists, Inc., 7272 Wisconsin Avenue, Bethesda, Maryland 20814.

† Use is not currently included in the labeling approved by the US Food and Drug Administration.

References

1. Pfizer. Neurontin (gabapentin) capsules, tablets, and oral solution prescribing information. New York, NY; April 2015.

2. Anon. Parke-Davis’ Neurontin recommended for approval as “add on” therapy for refractory seizures in epilepsy; gabapentin monotherapy trials under way. F-D-C Rep. 1992 Dec:7-8.

3. Anon. Warner Lambert’s Neurontin approved for adjunctive therapy in epilepsy patients Dec 30; “1P” drug does not interact with other anticonvulsants. F-D-C Rep. 1994 Jan:11.

4. Ramsay ER. Advances in the pharmacotherapy of epilepsy. Epilepsia. 1993; 34(Suppl 5):S9-16. [PubMed 8339715]

5. MacDonald RL, Kelly KM. Antiepileptic drug mechanisms of action. Epilepsia. 1993; 34(Suppl 5):S1-8. [IDIS 319353] [PubMed 7687957]

6. Goa KL, Sorkin EM. Gabapentin: a review of its pharmacological properties and clinical potential in epilepsy. Drugs. 1993; 46:409-27. [PubMed 7693432]

7. Graves NM, Leppik IE. Antiepileptic medications in development. DICP Ann Pharmacother. 1991; 25:978-86. [IDIS 285278] [PubMed 1949977]

8. UK Gabapentin Study Group. Gabapentin in partial epilepsy. Lancet. 1990; 335:1114-7. [IDIS 266256] [PubMed 1971862]

9. US Gabapentin Study Group. Gabapentin as add-on therapy in refractory partial epilepsy: a double blind, placebo-controlled, parallel-group study. Neurology. 1993; 43:2292-8. (IDIS 321974) [IDIS 321974] [PubMed 8232945]

10. Suman-Chauhan N, Webdale L, Hill DR et al. Characterisation of [3H] gabapentin binding to a novel site in rat brain: homogenate binding studies. Eur J Pharmacol. 1993; 244:293-301.

11. Hill DR, Suman-Chauhan N, Woodruff GN. Localization of [3H] gabapentin to a novel site in rat brain: autoradiogaphic studies. Eur J Pharmacol. 1993; 244: 303-9. [PubMed 8384571]

12. Anhut H, Leppik I, Schmidt B et al. Drug interaction study of the new anticonvulsant gabapentin with phenytoin in epileptic patients. Naunyn- Schmiedeberg Arch Pharmacol. 1988; 337(Suppl):R127. Abstract No. 507.

13. Graves NM, Leppik IE, Wagner ML et al. Effect of gabapentin on carbamazepine levels. Epilepsia. 1990; 31:644. Abstract.

14. Uthman BM, Hammond EJ, Wilder BJ. Absence of gabapentin and valproate interaction: an evoked potential and pharmacokinetic study. Epilepsia. 1990; 31:645. Abstract.

15. Hooper WD, Kavanagh MC, Herkes GK et al. Lack of a pharmacokinetic interaction between phenobarbitone and gabapentin. Br J Clin Pharmacol. 1991; 31:171-4. [IDIS 277831] [PubMed 2049232]

16. Parke-Davis, Morris Plains, NJ: Personal communication.

17. Taylor CP. Mechanism of action of new anti-epileptic drugs. In: Chadwick D, ed. New trends in epilepsy management: the role of gabapentin. London: Royal Society of Medicine Services Ltd; 1993:13-40.

18. Appleton R, Fichtner K, LaMoreaux L et al. Gabapentin as add-on therapy in children with refractory partial seizures: a 12-week, multicentre, double-blind, placebo-controlled study. Epilepsia. 1999; 40:1147-54. [IDIS 432135] [PubMed 10448830]

19. Pfizer, Morris Plains, NJ: Personal communication.

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