What are the side effects of gabapentin?

Side Effects of Gabapentin

Gabapentin commonly causes dizziness, somnolence, dry mouth, and constipation as its primary side effects, with approximately half of patients experiencing at least one adverse event during treatment. 1, 2

Common Side Effects

• Central Nervous System Effects:

  • Dizziness (28% of patients vs 8% on placebo) 2
  • Somnolence/drowsiness (21% of patients vs 5% on placebo) 2
  • Ataxia (3% of patients) 2
  • Unsteadiness/coordination problems 1, 2

• Gastrointestinal Effects:

  • Dry mouth (5% of patients vs 1% on placebo) 2
  • Constipation (4% of patients vs 2% on placebo) 2
  • Nausea (4% of patients vs 3% on placebo) 2
  • Vomiting (3% of patients vs 2% on placebo) 2

• Other Common Effects:

  • Peripheral edema (8% of patients vs 2% on placebo) 2
  • Weight gain (2% of patients) 2
  • Fatigue/asthenia 2

Serious Side Effects

• Neuropsychiatric Effects:

  • Suicidal thoughts or behavior (rare but serious - approximately 1 in 500 patients) 2
  • Changes in mood, depression, anxiety, or aggressive behavior 2
  • In pediatric patients (3-12 years): emotional lability, hostility, and hyperkinesia 2

• Allergic Reactions:

  • Serious or life-threatening allergic reactions affecting skin or other body parts 2
  • Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)/Multiorgan Hypersensitivity 2
  • Anaphylaxis and angioedema 2

• Other Serious Effects:

  • Increased risk of falls and fractures (1.81 per 100 person-years vs 1.34 in non-users) 3
  • Altered mental status (1.08 per 100 person-years vs 0.97 in non-users) 3
  • Risk of withdrawal-precipitated seizures if stopped suddenly 2

Dose-Related Side Effects

• Side effects are typically dose-related, with higher incidence at doses above 1800 mg/day 1, 4
• Clear dose-response relationship for falls or fractures, with highest risk at doses ≥2400 mg/day (RR 1.90) 3
• Most side effects are transient and occur during the titration phase 5
• Approximately 10% of patients discontinue gabapentin due to side effects in clinical trials for neuropathic pain 1

Special Populations and Considerations

• Elderly patients may be more susceptible to CNS side effects including dizziness and somnolence 2
• Patients with renal impairment require dose adjustment due to reduced clearance 2
• Patients with history of substance abuse should be monitored carefully as gabapentin has potential for misuse 1
• Patients with AUD (alcohol use disorder) may have elevated incidence of adverse effects regardless of gabapentin exposure 3

Practical Management of Side Effects

• Most side effects are mild to moderate and typically subside within approximately 10 days from initiation of treatment 4
• Slow titration can minimize side effects (starting at 300 mg/day and gradually increasing) 1, 4
• Unlike opioids, tolerance does not develop to most side effects 1
• Patients should not drive or operate heavy machinery until they know how gabapentin affects them 2
• Gabapentin should not be stopped abruptly due to risk of withdrawal seizures 2

Monitoring Recommendations

• Monitor for suicidal thoughts or behavior, especially at initiation of therapy or dose changes 2
• Watch for signs of allergic reactions including skin rash, fever, swollen glands, or yellowing of skin 2
• Regular monitoring for falls risk is recommended, especially at doses ≥600 mg/day 3
• Patients should be advised to report any unusual changes in mood or behavior 2

While gabapentin is generally well-tolerated compared to some other neuropathic pain medications, the side effect profile should be carefully considered when initiating therapy, particularly in vulnerable populations such as the elderly or those with comorbid conditions.