Can gabapentin cause hallucinations?

Can Gabapentin Cause Hallucinations?

Yes, gabapentin can cause hallucinations, particularly in patients with renal impairment, older adults, and those taking higher doses. This adverse effect is well-documented in case reports and clinical studies, though it remains relatively uncommon in the general population.

Evidence of Hallucinations as an Adverse Effect

Case Reports and Clinical Evidence

• Visual hallucinations have been directly attributed to gabapentin use in patients with no prior psychiatric history, with complete resolution after drug discontinuation 1
• A 65-year-old woman developed visual hallucinations occurring 2-3 times monthly while taking gabapentin 1800 mg/day, which completely resolved after stopping the medication and remained absent after 1 year of follow-up 1
• Gabapentin toxicity in patients with renal failure can manifest as confusion with hallucinations, along with myoclonus, tremulousness, and altered mental status 2
• A 46-year-old woman with acute renal failure developed hearing loss, myoclonus, and confusion with hallucinations in the presence of elevated gabapentin concentrations (17.6 μg/mL), with rapid improvement after hemodialysis 2

Risk Factors for Hallucinations

Renal impairment is the most critical risk factor because gabapentin is eliminated entirely by the kidneys and is not metabolized 3. Key considerations include:

• Higher doses significantly increase the risk of central nervous system adverse effects in older adults with chronic kidney disease 4
• Patients with CKD starting gabapentin at >300 mg/day had a 27% higher risk of hospital visits with encephalopathy compared to those starting at ≤300 mg/day (weighted risk ratio 1.27,95% CI 1.13-1.42) 4
• Hospitalization with altered mental status occurs in 1.27% of patients starting high-dose gabapentin (>600 mg/day) versus 1.06% with low-dose (≤600 mg/day) within 30 days 5

Perioperative Context

• Cyclobenzaprine, a structurally related medication, can cause hallucinations through anticholinergic effects, suggesting a class-related mechanism 6
• While gabapentin did not increase postoperative delirium rates in a large trial of 697 older adults (mean age 72 years), the study focused on delirium rather than specifically tracking hallucinations 6

Clinical Implications and Monitoring

Dosing Recommendations

• Start at the lowest possible dose (≤300 mg/day in patients with CKD or older adults) to minimize risk 4, 5
• The number needed to harm for hospitalization with altered mental status when using high-dose versus low-dose gabapentin is 477, indicating relatively low absolute risk but clinically meaningful when prescribing to large populations 5

Common Pitfalls to Avoid

• Do not overlook renal function before prescribing gabapentin, as impaired elimination dramatically increases toxicity risk 2
• Be vigilant for early signs of altered mental status including confusion, drowsiness, and visual disturbances, particularly in the first 30 days of therapy 5
• Gabapentin is not metabolized and does not induce liver enzymes, which reduces drug interaction risk but means dose adjustment is entirely dependent on renal function 3

When Hallucinations Occur

• Discontinue gabapentin immediately if hallucinations develop 1
• Consider hemodialysis in patients with renal failure and severe gabapentin toxicity, as it effectively removes the drug 2
• Symptoms typically resolve rapidly after drug discontinuation, with improvement often seen within hours to days 2, 1