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Neurontin

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Neurontin

Side Effects
Interactions

SIDE EFFECTS

The following serious adverse reactions are discussed in greater detail in other sections:

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

Postherpetic Neuralgia

The most commonly observed adverse reactions associated with the use of NEURONTIN in adults, not seen at an equivalent frequency among placebo-treated patients, were dizziness, somnolence, and peripheral edema.

In the 2 controlled studies in postherpetic neuralgia, 16% of the 336 patients who received NEURONTIN and 9% of the 227 patients who received placebo discontinued treatment because of an adverse reaction. The adverse reactions that most frequently led to withdrawal in NEURONTIN-treated patients were dizziness, somnolence, and nausea.

Incidence in Controlled Clinical Trials

Table 3 lists treatment-emergent signs and symptoms that occurred in at least 1% of NEURONTIN-treated patients with postherpetic neuralgia participating in placebo-controlled trials and that were numerically more frequent in the NEURONTIN group than in the placebo group. Adverse reactions were usually mild to moderate in intensity.

TABLE 3: Treatment-Emergent Adverse Reaction Incidence in Controlled Trials in Postherpetic Neuralgia (Reactions in at least 1% of NEURONTIN -Treated Patients and Numerically More Frequent Than in the Placebo Group)

Body System/ Preferred Term NEURONTIN
N=336 %
Placebo
N=227 %
Body as a Whole
  Asthenia 6 5
  Infection 5 4
  Accidental injury 3 1
Digestive System
  Diarrhea 6 3
  Dry mouth 5 1
  Constipation 4 2
  Nausea 4 3
  Vomiting 3 2
Metabolic and Nutritional Disorders
  Peripheral edema 8 2
  Weight gain 2 0
  Hyperglycemia 1 0
Nervous System
  Dizziness 28 8
  Somnolence 21 5
  Ataxia 3 0
  Thinking abnormal 3 0
  Abnormal gait 2 0
  Incoordination 2 0
Respiratory System
  Pharyngitis 1 0
Special Senses
  Amblyopiaa 3 1
  Conjunctivitis 1 0
  Diplopia 1 0
  Otitis media 1 0
aReported as blurred vision

Other reactions in more than 1% of patients but equally or more frequent in the placebo group included pain, tremor, neuralgia, back pain, dyspepsia, dyspnea, and flu syndrome.

There were no clinically important differences between men and women in the types and incidence of adverse reactions. Because there were few patients whose race was reported as other than white, there are insufficient data to support a statement regarding the distribution of adverse reactions by race.

Epilepsy

The most commonly observed adverse reactions associated with the use of NEURONTIN in combination with other antiepileptic drugs in patients > 12 years of age, not seen at an equivalent frequency among placebo-treated patients, were somnolence, dizziness, ataxia, fatigue, and nystagmus. The most commonly observed adverse reactions reported with the use of NEURONTIN in combination with other antiepileptic drugs in pediatric patients 3 to 12 years of age, not seen at an equal frequency among placebo-treated patients, were viral infection, fever, nausea and/or vomiting, somnolence, and hostility [see WARNINGS AND PRECAUTIONS].

Approximately 7% of the 2074 patients > 12 years of age and approximately 7% of the 449 pediatric patients 3 to 12 years of age who received NEURONTIN in premarketing clinical trials discontinued treatment because of an adverse reaction. The adverse reactions most commonly associated with withdrawal in patients > 12 years of age were somnolence (1.2%), ataxia (0.8%), fatigue (0.6%), nausea and/or vomiting (0.6%), and dizziness (0.6%). The adverse reactions most commonly associated with withdrawal in pediatric patients were emotional lability (1.6%), hostility (1.3%), and hyperkinesia (1.1%).

Incidence in Controlled Adjunctive Clinical Trials

Table 4 lists treatment-emergent signs and symptoms that occurred in at least 1% of NEURONTIN-treated patients > 12 years of age with epilepsy participating in placebo-controlled trials and were numerically more common in the NEURONTIN group. In these studies, either NEURONTIN or placebo was added to the patient's current antiepileptic drug therapy. Adverse reactions were usually mild to moderate in intensity.

TABLE 4: Treatment-Emergent Adverse Reaction Incidence in Controlled Add-On Trials In Patients > 12 years of age (Reactions in at least 1% of NEURONTIN patients and numerically more frequent than in the placebo group)

Body System/ Adverse Reaction NEURONTINa
N=543 %
Placeboa
N=378 %
Body As A Whole
  Fatigue 11 5
  Weight Increase 3 2
  Back Pain 2 1
  Peripheral Edema 2 1
Cardiovascular
  Vasodilatation 1 0
Digestive System
  Dyspepsia 2 1
  Mouth or Throat Dry 2 1
  Constipation 2 1
  Dental Abnormalities 2 0
Nervous System
  Somnolence 19 9
  Dizziness 17 7
  Ataxia 13 6
  Nystagmus 8 4
  Tremor 7 3
  Dysarthria 2 1
  Amnesia 2 0
  Depression 2 1
  Thinking Abnormal 2 1
  Coordination Abnormal 1 0
Respiratory System
  Pharyngitis 3 2
  Coughing 2 1
Skin and Appendages
  Abrasion 1 0
Urogenital System
  Impotence 2 1
Special Senses
  Diplopia 6 2
  Amblyopiab 4 1
aPlus background antiepileptic drug therapy
bAmblyopia was often described as blurred vision.

Among the treatment-emergent adverse reactions occurring at an incidence of at least 10% in NEURONTIN-treated patients, somnolence and ataxia appeared to exhibit a positive dose-response relationship.

The overall incidence of adverse reactions and the types of adverse reactions seen were similar among men and women treated with NEURONTIN. The incidence of adverse reactions increased slightly with increasing age in patients treated with either NEURONTIN or placebo. Because only 3% of patients (28/921) in placebo-controlled studies were identified as nonwhite (black or other), there are insufficient data to support a statement regarding the distribution of adverse reactions by race.

Table 5 lists treatment-emergent signs and symptoms that occurred in at least 2% of NEURONTIN-treated patients, age 3 to 12 years of age with epilepsy participating in placebo-controlled trials, and which were numerically more common in the NEURONTIN group. Adverse reactions were usually mild to moderate in intensity.

TABLE 5: Treatment-Emergent Adverse Reaction Incidence in Pediatric Patients Age 3 to 12 Years in a Controlled Add-On Trial (Reactions in at least 2% of NEURONTIN patients and numerically more frequent than in the placebo group)

Body System/Adverse Reaction NEURONTINa
N=119%
Placeboa
N=128%
Body As A Whole
  Viral Infection 11 3
  Fever 10 3
  Weight Increase 3 1
  Fatigue 3 2
Digestive System
  Nausea and/or Vomiting 8 7
Nervous System
  Somnolence 8 5
  Hostility 8 2
  Emotional Lability 4 2
  Dizziness 3 2
  Hyperkinesia 3 1
Respiratory System
  Bronchitis 3 1
  Respiratory Infection 3 1
aPlus background antiepileptic drug therapy

Other reactions in more than 2% of pediatric patients 3 to 12 years of age but equally or more frequent in the placebo group included: pharyngitis, upper respiratory infection, headache, rhinitis, convulsions, diarrhea, anorexia, coughing, and otitis media.

Postmarketing Experience

The following adverse reactions have been identified during postmarketing use of NEURONTIN. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

General disorders and administration site conditions: fever

Hepatobiliary disorders: jaundice

Investigations: blood glucose fluctuation, elevated creatine kinase, elevated liver function tests

Metabolism and nutrition disorders: hyponatremia

Nervous system disorders: movement disorder

Musculoskeletal and connective tissue disorders: rhabdomyolysis

Reproductive system and breast disorders: breast enlargement

Skin and subcutaneous tissue disorders: angioedema, erythema multiforme, Stevens-Johnson syndrome.

Adverse reactions following the abrupt discontinuation of gabapentin have also been reported. The most frequently reported reactions were anxiety, insomnia, nausea, pain, and sweating.

Read the Neurontin (gabapentin) Side Effects Center for a complete guide to possible side effects

DRUG INTERACTIONS

Other Antiepileptic Drugs

Gabapentin is not appreciably metabolized nor does it interfere with the metabolism of commonly coadministered antiepileptic drugs [see CLINICAL PHARMACOLOGY].

Hydrocodone

Coadministration of NEURONTIN (125 to 500 mg) decreases hydrocodone Cmax and AUC values in a dose-dependent manner. The Cmax and AUC values are 3% to 4% lower, respectively, after administration of 125 mg Neurontin and 21% to 22% lower, respectively, after administration of 500 mg NEURONTIN . Hydrocodone increases gabapentin AUC values by 14% [see CLINICAL PHARMACOLOGY].

Morphine

A literature article reported that when a 60 mg controlled-release morphine capsule was administered 2 hours prior to a 600 mg NEURONTIN capsule (N=12), mean gabapentin AUC increased by 44% compared to gabapentin administered without morphine [see PATIENT INFORMATION]. Morphine pharmacokinetic parameter values were not affected by administration of NEURONTIN 2 hours after morphine. The magnitude of interaction at other doses is not known.

Maalox® (aluminum hydroxide, magnesium hydroxide)

The mean bioavailability of gabapentin was reduced by about 20% with concomitant use of an antacid (Maalox®) containing magnesium and aluminum hydroxides. It is recommended that gabapentin be taken at least 2 hours following Maalox administration [see CLINICAL PHARMACOLOGY].

Drug/Laboratory Test Interactions

Because false positive readings were reported with the Ames N-Multistix SG® dipstick test for urinary protein when gabapentin was added to other antiepileptic drugs, the more specific sulfosalicylic acid precipitation procedure is recommended to determine the presence of urine protein.

Drug Abuse And Dependence

Controlled Substance

Gabapentin is not a scheduled drug.

Abuse

Gabapentin does not exhibit affinity for benzodiazepine, opiate (mu, delta or kappa), or cannabinoid 1 receptor sites. A small number of postmarketing cases report gabapentin misuse and abuse. These individuals were taking higher than recommended doses of gabapentin for unapproved uses. Most of the individuals described in these reports had a history of poly-substance abuse or used gabapentin to relieve symptoms of withdrawal from other substances. When prescribing gabapentin carefully evaluate patients for a history of drug abuse and observe them for signs and symptoms of gabapentin misuse or abuse (e.g. development of tolerance, self-dose escalation, and drug-seeking behavior).

Dependence

There are rare postmarketing reports of individuals experiencing withdrawal symptoms shortly after discontinuing higher than recommended doses of gabapentin used to treat illnesses for which the drug is not approved. Such symptoms included agitation, disorientation and confusion after suddenly discontinuing gabapentin that resolved after restarting gabapentin. Most of these individuals had a history of poly-substance abuse or used gabapentin to relieve symptoms of withdrawal from other substances. The dependence and abuse potential of gabapentin has not been evaluated in human studies.

Read the Neurontin Drug Interactions Center for a complete guide to possible interactions

Last reviewed on RxList: 8/28/2014
This monograph has been modified to include the generic and brand name in many instances.

Side Effects
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Neurontin - User Reviews

Neurontin User Reviews

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