Background: Gabapentin (GBP) may be useful in bipolar disorders, including as adjunctive therapy for bipolar depression, although controlled studies suggest inefficacy as primary treatment for mania or treatment-resistant rapid cycling.
Methods: We performed a 12-week trial of open GBP (mean dose 1725 mg/day) added to stable doses of mood stabilizers or atypical antipsychotics in 22 (10 women, mean age 38.4 years) depressed [28-item Hamilton Depression Rating Scale (HDRS) >18] bipolar (10 bipolar I, 12 bipolar II) disorder outpatients. Mean illness duration was 18.6 years; current depressive episode duration was 18.0 weeks. Prospective 28-item HDRS, Young Mania Rating Scale (YMRS) and Clinical Global Impression – Severity (CGI-S) ratings were obtained.
Results: Overall, HDRS ratings decreased 53% from 32.5 ± 7.7 at baseline to 16.5 ± 12.8 at week 12 (p < 0.0001). Twelve of 22 (55%) patients had moderate to marked improvement (HDRS decrease=50%) with HDRS decreasing 78% from 27.9 ± 6.2 to 6.2 ± 4.5 (p < 0.0001). Eight of 22 (36%) patients remitted (HDRS≥8). In non-responders, HDRS decreased from 38.0 ± 5.4 to 28.9 ± 6.7 (p=0.005). Ten of 13 (77%) mild to moderately depressed (baseline HDRS >18 and <35) patients responded, while only two of nine patients (22%) with severe depression (HDRS ? 35) responded (p < 0.03). Both groups, however, had similar, statistically significant HDRS decreases. GBP was well tolerated.
Conclusion: Open adjunctive GBP was effective and well tolerated in patients with mild to moderate bipolar depression. This open pilot study must be viewed with caution, and randomized controlled studies are warranted.