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

  • Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)/Multiorgan Hypersensitivity [see WARNINGS AND PRECAUTIONS]
  • Somnolence/Sedation and Dizziness [see WARNINGS AND PRECAUTIONS]
  • Withdrawal Precipitated Seizure, Status Epilepticus [see WARNINGS AND PRECAUTIONS]
  • Suicidal Behavior and Ideation [see WARNINGS AND PRECAUTIONS]
  • Neuropsychiatric Adverse Reactions (Pediatric Patients 3-12 Years of Age) [see WARNINGS AND PRECAUTIONS]
  • Sudden and Unexplained Death in Patients with Epilepsy [see WARNINGS AND PRECAUTIONS]

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.