Prescription Drug Information: Gabapentin (Page 4 of 6)

Incidence in Controlled Clinical Trials

Table 2 lists treatment-emergent signs and symptoms 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. Adverse events were usually mild to moderate in intensity.

TABLE 2. Treatment-Emergent Adverse Event Incidence in Controlled Trials in Postherpetic Neuralgia (Events in at least 1% of Gabapentin-Treated Patients and Numerically More Frequent Than in the Placebo Group)
Body System/ Preferred Term GabapentinN=336% PlaceboN=227%
*
Reported as blurred vision
Body As A Whole
Asthenia 5.7 4.8
Infection 5.1 3.5
Headache 3.3 3.1
Accidental injury 3.3 1.3
Abdominal pain 2.7 2.6
Digestive System
Diarrhea 5.7 3.1
Dry mouth 4.8 1.3
Constipation 3.9 1.8
Nausea 3.9 3.1
Vomiting 3.3 1.8
Flatulence 2.1 1.8
Metabolic and Nutritional Disorders
Peripheral edema 8.3 2.2
Weight gain 1.8 0.0
Hyperglycemia 1.2 0.4
Nervous System
Dizziness 28.0 7.5
Somnolence 21.4 5.3
Ataxia 3.3 0.0
Thinking abnormal 2.7 0.0
Abnormal gait 1.5 0.0
Incoordination 1.5 0.0
Amnesia 1.2 0.9
Hypesthesia 1.2 0.9
Respiratory System
Pharyngitis 1.2 0.4
Skin and Appendages
Rash 1.2 0.9
Special Senses
Amblyopia * 2.7 0.9
Conjunctivitis 1.2 0.0
Diplopia 1.2 0.0
Otitis media 1.2 0.0

Other events 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 events. 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 events by race.

Epilepsy

The most commonly observed adverse events associated with the use of 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 commonly observed adverse events reported 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, Neuropsychiatric Adverse Events).

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 event. The adverse events 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 events most commonly associated with withdrawal in pediatric patients were emotional lability (1.6%), hostility (1.3%), and hyperkinesia (1.1%).

Incidence in Controlled Clinical Trials

Table 3 lists treatment-emergent signs and symptoms 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. Adverse events were usually mild to moderate in intensity.

The prescriber should be aware that these figures, obtained when gabapentin was added to concurrent antiepileptic drug therapy, cannot be used to predict the frequency of adverse events in the course of usual medical practice where patient characteristics and other factors may differ from those prevailing during clinical studies. Similarly, the cited frequencies cannot be directly compared with figures obtained from other clinical investigations involving different treatments, uses, or investigators. An inspection of these frequencies, however, does provide the prescribing physician with one basis to estimate the relative contribution of drug and nondrug factors to the adverse event incidences in the population studied.

TABLE 3. Treatment-Emergent Adverse Event Incidence in Controlled Add-On Trials In Patients >12 years of age (Events in at Least 1% of Gabapentin Patients and Numerically More Frequent than in the Placebo Group)
Body System/ Adverse Event Gabapentin *N=543% Placebo *N=378%
*
Plus background antiepileptic drug therapy
Amblyopia was often described as blurred vision
Body As A Whole
Fatigue 11.0 5.0
Weight Increase 2.9 1.6
Back Pain 1.8 0.5
Peripheral Edema 1.7 0.5
Cardiovascular
Vasodilatation 1.1 0.3
Digestive System
Dyspepsia 2.2 0.5
Mouth or Throat Dry 1.7 0.5
Constipation 1.5 0.8
Dental Abnormalities 1.5 0.3
Increased Appetite 1.1 0.8
Hematologic and Lymphatic Systems
Leukopenia 1.1 0.5
Musculoskeletal System
Myalgia 2.0 1.9
Fracture 1.1 0.8
Nervous System
Somnolence 19.3 8.7
Dizziness 17.1 6.9
Ataxia 12.5 5.6
Nystagmus 8.3 4.0
Tremor 6.8 3.2
Nervousness 2.4 1.9
Dysarthria 2.4 0.5
Amnesia 2.2 0.0
Depression 1.8 1.1
Thinking Abnormal 1.7 1.3
Twitching 1.3 0.5
Coordination Abnormal 1.1 0.3
Respiratory System
Rhinitis 4.1 3.7
Pharyngitis 2.8 1.6
Coughing 1.8 1.3
Skin and Appendages
Abrasion 1.3 0.0
Pruritus 1.3 0.5
Urogenital System
Impotence 1.5 1.1
Special Senses
Diplopia 5.9 1.9
Amblyopia 4.2 1.1
Laboratory Deviations
WBC Decreased 1.1 0.5

Other events in more than 1% of patients >12 years of age but equally or more frequent in the placebo group included: headache, viral infection, fever, nausea and/or vomiting, abdominal pain, diarrhea, convulsions, confusion, insomnia, emotional lability, rash, acne.

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

The overall incidence of adverse events and the types of adverse events seen were similar among men and women treated with gabapentin. The incidence of adverse events 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 events by race.

Table 4 lists treatment-emergent signs and symptoms 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 were numerically more common in the gabapentin group. Adverse events were usually mild to moderate in intensity.

TABLE 4. Treatment-Emergent Adverse Event Incidence in Pediatric Patients Age 3 to 12 Years in a Controlled Add-On Trial (Events in at least 2% of Gabapentin patients and numerically more frequent than in the placebo group)
Body System/ Adverse Event Gabapentin *N=119% Placebo *N=128%
*
Plus background antiepileptic drug therapy
Body As A Whole
Viral Infection 10.9 3.1
Fever 10.1 3.1
Weight Increase 3.4 0.8
Fatigue 3.4 1.6
Digestive System
Nausea and/or Vomiting 8.4 7.0
Nervous System
Somnolence 8.4 4.7
Hostility 7.6 2.3
Emotional Lability 4.2 1.6
Dizziness 2.5 1.6
Hyperkinesia 2.5 0.8
Respiratory System
Bronchitis 3.4 0.8
Respiratory Infection 2.5 0.8

Other events 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.

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