What are the side effects of gabapentin?

Side Effects of Gabapentin

The most common side effects of gabapentin include somnolence, dizziness, and ataxia, with approximately 10% of patients discontinuing treatment due to adverse effects. 1

Common Side Effects

Gabapentin's side effect profile is well-documented in both FDA labeling and clinical guidelines. The most frequently reported adverse effects include:

Central Nervous System Effects

• Somnolence/sedation (19-21%) 1, 2
• Dizziness (17-28%) 1, 2
• Ataxia (13%) 1
• Fatigue (11%) 1
• Nystagmus (8%) 1
• Tremor (7%) 1
• Thinking abnormal (2-3%) 1

Gastrointestinal Effects

• Dry mouth (5%) 1
• Nausea (4%) 1
• Constipation (4%) 1
• Diarrhea (6%) 1
• Vomiting (3%) 1

Other Common Effects

• Peripheral edema (7-8%) 3, 1
• Weight gain (2-3%) 2, 1
• Visual disturbances (amblyopia/blurred vision) (3-4%) 1
• Diplopia (6%) 1

Serious Side Effects

While generally well-tolerated, gabapentin can cause several serious adverse effects that require monitoring:

• Suicidal thoughts and behavior: Like other antiepileptic drugs, gabapentin carries an increased risk of suicidal thoughts or actions (approximately 1 in 500 patients) 1

• Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)/Multiorgan Hypersensitivity: A rare but serious allergic reaction 1

• Neuropsychiatric effects: Particularly in pediatric patients 3-12 years of age, including emotional lability, hostility, and hyperkinesia 1

• Withdrawal-precipitated seizures: Abrupt discontinuation can lead to increased seizure frequency 1

• Cardiovascular effects: Rare cases of atrial fibrillation have been reported, particularly in older adults 4

Side Effect Rates and Discontinuation

• Approximately 11% of patients discontinue gabapentin due to adverse effects compared to 8.2% with placebo 5

• In clinical trials for hot flashes, about 10% of patients discontinued gabapentin due to side effects, which is lower than the 40% discontinuation rate seen with clonidine 3

• Side effects are typically transient and dose-related, with most adverse events occurring during the titration phase 6

Factors Affecting Side Effect Risk

Several factors can increase the risk of experiencing side effects:

• Dose: Higher doses (>900 mg daily) are associated with increased efficacy but also more side effects 2, 7

• Age: Elderly patients may be more susceptible to adverse effects, particularly neuropsychological reactions 2

• Renal impairment: Gabapentin requires dose adjustment in patients with reduced kidney function 2

• Concomitant medications: Combining gabapentin with other CNS depressants can increase sedation 1

Management of Side Effects

To minimize adverse effects:

1. Start low, go slow: Begin with lower doses (300 mg once daily) and gradually titrate up 2

2. Divided dosing: Administer in three divided doses to minimize peak-related side effects 2

3. Evening dosing: Taking a larger portion of the daily dose at bedtime can help manage sedation 2

4. Monitor closely: Particularly during dose adjustments and in high-risk populations 1

5. Avoid abrupt discontinuation: Taper gradually to prevent withdrawal symptoms 1

Comparison to Other Medications

When compared to other medications used for similar indications:

• Gabapentin has fewer cardiovascular side effects than tricyclic antidepressants 3

• It has a more favorable side effect profile than opioids for neuropathic pain 3

• Compared to pregabalin, gabapentin requires slower titration and higher doses but has similar types of side effects 2

Gabapentin's side effect profile should be carefully considered when selecting treatment, particularly in elderly patients or those with comorbidities that might increase risk of adverse effects.