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 Neuralgiaa Reported as blurred vision
|
| Gabapentin
N=336
%
| Placebo
N=227
%
|
Body as a Whole Asthenia
Infection
Accidental injury
|
6
5
3
|
5
4
1
|
Digestive System Diarrhea
Dry mouth
Constipation
Nausea
Vomiting
|
6
5
4
4
3
|
3
1
2
3
2
|
Metabolic and Nutritional Disorders Peripheral edema
Weight gain
Hyperglycemia
|
8
2
1
|
2
0
0
|
Nervous System Dizziness
Somnolence
Ataxia
Abnormal thinking
Abnormal gait
Incoordination
|
28
21
3
3
2
2
|
8
5
0
0
0
0
|
Respiratory System Pharyngitis
|
1
|
0
|
Special Senses Amblyopia
a Conjunctivitis
Diplopia
Otitis media
|
3
1
1
1
|
1
0
0
0
|
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 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 (5.7)]
.
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
a Plus background antiepileptic drug therapy
b Amblyopia was often described as blurred vision.
|
| Gabapentin
a N=543
%
| Placebo
a N=378
%
|
Body As A Whole Fatigue
Increased Weight
Back Pain
Peripheral Edema
|
11
3
2
2
|
5
2
1
1
|
Cardiovascular Vasodilatation
|
1
|
0
|
Digestive System Dyspepsia
Dry Mouth or Throat
Constipation
Dental Abnormalities
|
2
2
2
2
|
1
1
1
0
|
Nervous System Somnolence
Dizziness
Ataxia
Nystagmus
Tremor
Dysarthria
Amnesia
Depression
Abnormal thinking
Abnormal coordination
|
19
17
13
8
7
2
2
2
2
1
|
9
7
6
4
3
1
0
1
1
0
|
Respiratory System Pharyngitis
Coughing
|
3
2
|
2
1
|
Skin and Appendages Abrasion
|
1
|
0
|
Urogenital System Impotence
|
2
|
1
|
Special Senses Diplopia
Amblyopia
b
|
6
4
|
2
1
|
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
a Plus background antiepileptic drug therapy
|
| Gabapentin
a N=119
%
| Placebo
a N=128
%
|
Body As A Whole Viral Infection
Fever
Increased Weight
Fatigue
|
11
10
3
3
|
3
3
1
2
|
Digestive System Nausea and/or Vomiting
|
8
|
7
|
Nervous System Somnolence
Hostility
Emotional Lability
Dizziness
Hyperkinesia
|
8
8
4
3
3
|
5
2
2
2
1
|
Respiratory System Bronchitis
Respiratory Infection
|
3
3
|
1
1
|
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.