Gabapentin Side Effects
Most Common Side Effects
Gabapentin most commonly causes dizziness (17-28%), somnolence (19-21%), and peripheral edema (8%), with most side effects being mild to moderate and improving significantly after the first week of treatment. 1, 2
Central Nervous System Effects
- Dizziness occurs in 17-28% of patients and is the most frequent reason for discontinuation 1, 2
- Somnolence/drowsiness affects 19-21% of patients 1, 2
- Ataxia (unsteadiness/coordination problems) occurs in 13% of patients taking gabapentin for epilepsy and 3% for postherpetic neuralgia 1, 2
- Fatigue affects 11% of patients 2
- Nystagmus (abnormal eye movements) occurs in 8% of patients 2
- Tremor affects 7% of patients 2
Other Common Side Effects
- Peripheral edema (leg/feet swelling) occurs in 8% of patients with postherpetic neuralgia 1, 2
- Weight gain affects 2-3% of patients 1, 2
- Dry mouth occurs in 5% of patients 2
- Constipation affects 4% of patients 2
- Nausea occurs in 4% of patients 2
- Diplopia (double vision) affects 6% of patients with epilepsy 2
Serious Side Effects (Rare but Critical)
Suicidal Thoughts and Behavior
- Suicidal ideation occurs in approximately 1 in 500 patients (0.2%) taking gabapentin 1, 2
- Patients should be monitored for new or worsening depression, anxiety, agitation, panic attacks, insomnia, irritability, aggressive behavior, or thoughts about suicide 2
Severe Allergic Reactions
- Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) can occur, potentially affecting skin, liver, or blood cells 2
- Anaphylaxis and angioedema have been reported in postmarketing surveillance 2
- Warning signs include: skin rash, hives, difficulty breathing, swollen glands, facial/lip/throat swelling, yellowing of skin/eyes, unusual bruising/bleeding, severe fatigue, or frequent infections 2
Neuropsychiatric Effects in Children
- In pediatric patients ages 3-12 years, gabapentin can cause emotional changes, aggressive behavior, problems with concentration, restlessness, changes in school performance, and hyperactivity 2
- Hostility occurs in 8% of pediatric patients versus 2% with placebo 2
Time Course and Management of Side Effects
Temporal Pattern
- Most side effects are transient, improving markedly after the first week and largely resolving by week 4 1
- Side effects during the initial titration phase are common but typically do not require discontinuation 1, 3
Dose-Related Considerations
- Side effects are dose-dependent, with higher incidence at doses above 1800 mg/day 1
- Approximately 10% of patients discontinue gabapentin due to side effects in clinical trials 1
- Higher doses (>600 mg/day) are associated with increased risk of altered mental status requiring hospitalization (1.27% vs 1.06% for lower doses) 4
Minimizing Side Effects
- Slow titration starting at 300 mg/day can minimize adverse effects: increase to 600 mg on day 2, then 900 mg on day 3 1
- Unlike opioids, tolerance does not develop to most gabapentin side effects 1
Special Population Considerations
Renal Impairment
- Dose adjustment is mandatory in patients with kidney problems or on hemodialysis due to reduced clearance 1, 2
Drug Interactions and Advantages
- Gabapentin has no significant drug interactions and does not inhibit CYP2D6 1
- Does not cause sexual dysfunction, making it advantageous over SSRIs/SNRIs 1
- No withdrawal syndrome occurs with gabapentin discontinuation, though gradual tapering is still recommended to avoid seizure precipitation in epilepsy patients 1, 2
Critical Safety Warnings
Abrupt Discontinuation
- Never stop gabapentin suddenly without medical supervision - this can cause serious problems including status epilepticus in epilepsy patients 2
Impaired Driving and Activities
- Gabapentin can slow thinking and motor skills, causing sleepiness and dizziness that increase risk of accidental injury and falls 2
- Patients should not drive or operate heavy machinery until they know how gabapentin affects them 2
Alcohol and CNS Depressants
- Avoid alcohol and other CNS depressants as they can worsen sleepiness and dizziness 2