What are the side effects of gabapentin (Neurontin)?

Gabapentin Side Effects

The most common side effects of gabapentin include dizziness, drowsiness, and unsteadiness, which can significantly impact quality of life and increase the risk of falls or fractures, especially at doses above 600 mg/day. 1, 2

Common Side Effects

Gabapentin (Neurontin) is associated with several common side effects:

• Central Nervous System Effects:

  • Somnolence/drowsiness (21% vs 5% placebo) 1
  • Dizziness (28% vs 8% placebo) 1
  • Ataxia (loss of coordination) (3% vs 0% placebo) 1
  • Abnormal thinking 1
  • Abnormal gait 1

• Gastrointestinal Effects:

  • Dry mouth (5% vs 1% placebo) 1
  • Nausea (4% vs 3% placebo) 1
  • Constipation (4% vs 2% placebo) 1
  • Diarrhea (6% vs 3% placebo) 1
  • Vomiting (3% vs 2% placebo) 1

• Other Common Side Effects:

  • Peripheral edema (8% vs 2% placebo) 1
  • Weight gain (2% vs 0% placebo) 1
  • Visual disturbances (diplopia, blurred vision) 1

Serious Side Effects

While gabapentin is generally considered to have a better safety profile than some other anticonvulsants, it can cause serious adverse effects:

• Suicidal thoughts and behavior - Like other antiepileptic drugs, gabapentin may increase the risk of suicidal thoughts or actions in approximately 1 in 500 people 1

• Neuropsychiatric effects - Can cause emotional changes, aggressive behavior, problems with concentration, and changes in behavior, particularly in children 3-12 years 1

• Severe allergic reactions - May cause serious or life-threatening allergic reactions affecting skin, liver, or blood cells 1

• Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) - A rare but serious condition 1

• Withdrawal seizures - Abrupt discontinuation can precipitate seizures, even in patients without epilepsy 1

Risk Factors for Adverse Effects

Certain populations may be at higher risk for gabapentin side effects:

• Elderly patients - More susceptible to CNS side effects like dizziness and somnolence 2

• Patients with renal impairment - Gabapentin is primarily eliminated through the kidneys, so dosage adjustment is necessary 3

• Patients taking other CNS depressants - Increased risk of sedation when combined with other medications that cause drowsiness 1

• Dose-dependent risk - A clear dose-response relationship exists for falls or fractures, with highest risk observed at doses ≥2,400 mg/day (RR 1.90) 2

Monitoring and Management

To minimize adverse effects:

1. Start low, go slow - Begin with lower doses and gradually titrate up to minimize side effects

2. Monitor for neuropsychiatric symptoms - Watch for changes in mood, behavior, or thoughts of suicide

3. Avoid abrupt discontinuation - Taper gabapentin gradually to prevent withdrawal symptoms 1

4. Regular monitoring - Particularly important for patients on higher doses (≥600 mg/day) 2

5. Fall prevention strategies - Especially important for elderly patients due to increased risk of falls and fractures 2

Special Considerations

• Overdose effects - Even large overdoses typically cause minimal toxicity, with drowsiness, dizziness, and ataxia being the most common effects 4

• Rare but reported psychotic and depressive symptoms - Some case reports indicate gabapentin may induce psychotic or depressive symptoms in certain individuals 5

• Discontinuation symptoms - While less common than with some medications, gabapentin discontinuation symptoms can occur and should be managed with gradual tapering 6

• Efficacy vs. side effects - In clinical trials for neuropathic pain, approximately 10% of patients discontinued gabapentin due to side effects, primarily somnolence and dizziness 6, 7

When prescribing gabapentin, it's essential to weigh the potential benefits against these side effects, particularly for patients at higher risk of falls or with pre-existing cognitive impairment. The side effect profile should be discussed with patients before initiating therapy, with clear instructions to report any concerning symptoms.