GABAPENTIN (Page 2 of 7)

6 ADVERSE REACTIONS

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 (5.1)]
  • Anaphylaxis and Angioedema [see Warnings and Precautions (5.2)]
  • Somnolence/Sedation and Dizziness [see Warnings and Precautions (5.4)]
  • Withdrawal Precipitated Seizure, Status Epilepticus [see Warnings and Precautions (5.5)]
  • Suicidal Behavior and Ideation [see Warnings and Precautions (5.6)]
  • Respiratory Depression [see Warnings and Precautions (5.7)]
  • Neuropsychiatric Adverse Reactions (Pediatric Patients 3 to 12 Years of Age) [see Warnings and Precautions (5.8)]
  • Sudden and Unexplained Death in Patients with Epilepsy [see Warnings and Precautions (5.10)

6.1 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 common adverse reactions associated with the use of gabapentin in adults, not seen at an equivalent frequency among placebo-treated patients, were dizziness, somnolence, and peripheral edema.

In the 2 controlled trials in postherpetic neuralgia, 16% of the 336 patients who received gabapentin 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 gabapentin-treated patients were dizziness, somnolence, and nausea.

Table 3 lists adverse reactions that occurred in at least 1% of gabapentin-treated patients with postherpetic neuralgia participating in placebo-controlled trials and that were numerically more frequent in the gabapentin group than in the placebo group.

TABLE 3. Adverse Reactions in Pooled Placebo-Controlled Trials in Postherpetic Neuralgia

Gabapentin Placebo
N=336 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
Abnormal thinking 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

a Reported 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 with Partial Onset Seizures (Adjunctive Therapy)

The most common adverse reactions with gabapentin 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 common adverse reactions with the use of gabapentin 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 (5.8)].

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 gabapentin 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%).

Table 4 lists adverse reactions that occurred in at least 1% of gabapentin-treated patients >12 years of age with epilepsy participating in placebo-controlled trials and were numerically more common in the gabapentin group. In these studies, either gabapentin or placebo was added to the patient’s current antiepileptic drug therapy.

TABLE 4. Adverse Reactions in Pooled Placebo-Controlled Add-On Trials In Epilepsy Patients >12 years of age

Gabapentina N = 543 % Placeboa N = 378 %
Body As A Whole
Fatigue 11 5
Increased Weight 3 2
Back Pain 2 1
Peripheral Edema 2 1
Cardiovascular
Vasodilatation 1 0
Digestive System
Dyspepsia 2 1
Dry Mouth or Throat 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
Abnormal thinking 2 1
Abnormal coordination 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

a Plus background antiepileptic drug therapy

b Amblyopia was often described as blurred vision.

Among the adverse reactions occurring at an incidence of at least 10% in gabapentin-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 gabapentin. The incidence of adverse reactions increased slightly with increasing age in patients treated with either gabapentin 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 adverse reactions that occurred in at least 2% of gabapentin -treated patients, age 3 to 12 years of age with epilepsy participating in placebo-controlled trials, and which were numerically more common in the gabapentin group.

TABLE 5. Adverse Reactions in a Placebo-Controlled Add-On Trial in Pediatric Epilepsy Patients Age 3 to 12 Years

Gabapentina N = 119 % Placeboa N = 128 %
Body As A Whole
Viral Infection 11 3
Fever 10 3
Increased Weight 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

a Plus 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.

6.2 Postmarketing Experience

The following adverse reactions have been identified during postmarketing use of gabapentin. 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.

Hepatobiliary disorders: jaundice

Investigations: elevated creatine kinase, elevated liver function tests

Metabolism and nutrition disorders: hyponatremia

Musculoskeletal and connective tissue disorder: rhabdomyolysis

Nervous system disorders: movement disorder

Psychiatric disorders: agitation

Reproductive system and breast disorders: breast enlargement, changes in libido, ejaculation disorders and anorgasmia

Skin and subcutaneous tissue disorders: angioedema, [see Warnings and Precautions (5.2)], bullous pemphigoid, erythema multiforme, Stevens-Johnson syndrome.

There are postmarketing reports of life-threatening or fatal respiratory depression in patients taking gabapentin with opioids or other CNS depressants, or in the setting of underlying respiratory impairment [see Warnings and Precautions (5.7)].

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

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