Gabapentin Dosing for Anxiety Disorders in Adults
Gabapentin is not a guideline-recommended first-line treatment for anxiety disorders in adults, and there is insufficient high-quality evidence to support a standard dosing protocol for this indication. 1
Guideline-Recommended First-Line Treatments
SSRIs are the established first-line pharmacotherapy for anxiety disorders, including social anxiety disorder and generalized anxiety disorder. 1 Gabapentin lacks the robust evidence base that supports SSRIs and SNRIs for anxiety treatment, with only limited case reports and one negative placebo-controlled trial in panic disorder. 2, 3
Available Evidence for Gabapentin in Anxiety
Clinical Trial Data
- A randomized, double-blind, placebo-controlled trial in panic disorder (n=103) showed no overall benefit of gabapentin versus placebo on the primary outcome measure (Panic and Agoraphobia Scale, p=0.606). 3
- Post-hoc analysis suggested possible benefit only in more severely ill patients (PAS score ≥20), with women showing greater response than men regardless of treatment. 3
- Dosing in this trial ranged flexibly from 600-3600 mg/day over 8 weeks. 3
Case Report Evidence
- One case report documented a dose-response pattern in a 59-year-old woman with generalized anxiety disorder who had discontinued benzodiazepines after 7+ years of use. 2
- The specific doses used and response patterns were not quantified in the published abstract. 2
Off-Label Dosing Extrapolated from Other Indications
If gabapentin is considered for anxiety despite lack of guideline support, dosing patterns from approved indications (neuropathic pain, PTSD-associated nightmares) suggest:
Initial Dosing Strategy
- Start: 100-300 mg at bedtime on day 1 to minimize dizziness and sedation. 4
- Day 2-3: Increase to 300 mg three times daily (900 mg/day total). 4
- Titration: Increase by 300 mg every 3-7 days as tolerated. 4
Target Dose Range
- Minimum effective dose: 1800 mg/day divided three times daily (600 mg TID). 4
- Maximum dose: 3600 mg/day divided three times daily (1200 mg TID). 4
- Three-times-daily dosing is essential due to saturable, nonlinear absorption pharmacokinetics. 4
Duration of Adequate Trial
- Minimum trial: 3-8 weeks for titration plus 2 weeks at maximum tolerated dose, potentially requiring 2 months total before declaring treatment failure. 4
Special Population Considerations
Elderly or Medically Frail Patients
- Start at the lower end of dosing range (100 mg at bedtime). 4
- Use slower titration with increases every 3-7 days or longer to reduce fall risk from dizziness. 4
Renal Impairment
- Mandatory dose reduction based on creatinine clearance, as gabapentin is eliminated 98% by renal excretion. 4, 5
Common Side Effects
- Somnolence (80% in some trials), dizziness (23%), and headache are the most common adverse effects. 1, 3, 5
- Side effects are dose-dependent and typically mild to moderate. 5
Critical Clinical Pitfalls
- Do not use once-daily or twice-daily dosing for standard gabapentin formulations due to saturable absorption. 4
- Do not discontinue abruptly—taper gradually over at least 1 week to avoid withdrawal symptoms including anxiety rebound, tremor, and tachycardia. 6
- Do not rush titration in elderly patients, as this increases fall risk. 4
- Allow the full 2-month trial period before declaring treatment failure, as efficacy develops gradually. 4
Recommended Clinical Approach
Given the lack of guideline support and negative controlled trial data, gabapentin should only be considered for anxiety disorders when:
- First-line treatments (SSRIs, SNRIs) have failed or are contraindicated. 1
- The patient has comorbid conditions where gabapentin may provide dual benefit (e.g., neuropathic pain, PTSD-associated nightmares). 1, 4
- Benzodiazepines are being tapered and an alternative anxiolytic is needed. 2
If used, start at 300 mg three times daily (900 mg/day), titrate by 300 mg every 3-7 days to a target of 1800-3600 mg/day in three divided doses, and allow 6-8 weeks for adequate trial before assessing efficacy. 4, 3