Can gabapentin (anticonvulsant medication) cause tremors as a side effect?

Gabapentin and Tremor: A Complex Relationship

Yes, gabapentin can cause tremor as a side effect, but paradoxically it is also used to treat certain types of tremor, particularly orthostatic tremor. 1

Gabapentin-Induced Tremor as an Adverse Effect

Common Adverse Effects

• Tremor is a recognized side effect of gabapentin, listed in the FDA drug label alongside other neurological symptoms 1
• The most common adverse effects include lack of coordination, feeling drowsy, difficulty with speaking, tremor, jerky movements, difficulty with coordination, and unusual eye movement 1
• In clinical practice, tremor occurs as part of a constellation of motor symptoms that can develop with gabapentin use 2

Tremor in the Context of Gabapentin Toxicity

• At supratherapeutic doses, gabapentin can cause diffuse action tremors and tongue tremors as part of a toxicity syndrome 3
• A case report documented a patient taking 9600 mg daily (far exceeding typical dosing) who developed stimulus-sensitive myoclonus, painful muscle spasms, myokymia, and diffuse action tremors with a gabapentin level of 25.8 μg/mL (reference range 2.0-20.0 μg/mL) 3
• These motor symptoms, including tremor, resolved after a brief medication holiday and dose reduction 3

Clinical Implications for Adverse Tremor

• Elderly patients are at higher risk for adverse neurological effects and should receive lower starting doses with slower titration 2
• The FDA label recommends starting at 300 mg three times daily for most indications, though alternative dosing regimens may be considered 1
• Sedation and dizziness frequently accompany tremor as adverse effects, which may be particularly problematic in ambulatory patients 2

Gabapentin as Treatment for Tremor

Orthostatic Tremor

• Gabapentin is highly effective for orthostatic tremor, with patients reporting 60-80% improvement (mean 73%) at doses ranging from 300-1800 mg/day 4
• In a double-blind crossover study, gabapentin induced disappearance of orthostatic tremor in three of four patients and consistent reduction in one patient 5
• The response duration has ranged from 2-22 months (mean 11 months) with sustained benefit 4
• Gabapentin may be superior to clonazepam for orthostatic tremor, as five of seven patients in one series had previously failed clonazepam therapy 4

Essential Tremor

• For essential tremor, the evidence is mixed and less compelling 6
• A double-blind, placebo-controlled crossover trial (N=25) evaluating 1800 mg/day and 3600 mg/day showed statistically significant improvements in patient global assessments (p<0.05), observed tremor scores (p<0.005), water pouring scores (p<0.05), and activities of daily living scores (p<0.005) 6
• However, accelerometry scores, spirographs, and investigator global impression scores did not improve, suggesting subjective rather than objective benefit 6
• The results were similar for both high and low doses, with no significant predictors for response identified 6

Clinical Decision-Making Algorithm

When evaluating tremor in a patient on gabapentin:

1. Determine temporal relationship: Did tremor begin or worsen after starting gabapentin? 1
2. Assess dosing: Is the patient taking supratherapeutic doses or has renal impairment that could lead to accumulation? 1, 3
3. Evaluate tremor type: Is this action tremor, resting tremor, or orthostatic tremor? 4, 6
4. Check for other toxicity signs: Look for concurrent myoclonus, myokymia, ataxia, dizziness, or altered mental status 1, 3

Management approach:

• If tremor is an adverse effect: Consider dose reduction or medication holiday, as symptoms typically resolve within days 3
• If treating orthostatic tremor: Gabapentin 300-1800 mg/day is appropriate first-line therapy, particularly if clonazepam has failed 4, 5
• If treating essential tremor: Consider gabapentin as second-line therapy after propranolol and primidone, recognizing that evidence is weaker than for orthostatic tremor 7, 6

Important Caveats

• Renal function is critical: Gabapentin is not metabolized and is renally excreted, so patients with kidney disease or those on hemodialysis require dose adjustment 1
• Drug interactions are minimal: Gabapentin is not protein-bound and does not induce liver enzymes, reducing interaction potential 8
• Antacid timing matters: If taking aluminum/magnesium-containing antacids, wait at least 2 hours before the next gabapentin dose 1
• Side effects are generally mild, transient, and dose-related, with somnolence, fatigue, ataxia, and dizziness being most common 8