Gabapentin in Headache Disorders: What Is the Evidence?

OBJECTIVE: Gabapentin (GBP), originally an antiepileptic drug, is more commonly used in the treatment of pain, including headache disorders. Off-label GBP is used in headache disorders with some success, some failure, and much debate. Due to this ambiguity, a clinical evidence literature review was performed investigating GBP's efficacy in headache disorders. METHODS: Bibliographic reference searches for GBP use in headache disorders were performed in PUBMED and OVID Medline search engines from January 1, 1983 to August 31, 2014. Based on abstracts read by two reviewers, references were excluded if: GBP was not a study compound or headache symptoms were not studied. The resulting references were then read, reviewed, and analyzed. RESULTS: Fifty-six articles pertinent to GBP use in headache disorders were retained. Eight headache clinical trials were quality of evidence Class 2 or higher based on American Academy of Neurology criteria. Seven of the eight clinical trials showed statistically significant clinical benefit from GBP in various headache syndromes (though modest affects at times). One study, Mathew et al., had concerns about intention-treat analysis breaches and primary outcomes. CONCLUSION: Despite the conflicting evidence surrounding select studies, a significant amount of evidence shows that GBP has benefit for a majority of primary headache syndromes, including chronic daily headaches. GBP has some efficacy in migraine headache, but not sufficient evidence to suggest primary therapy. When primary headache treatments fail, a GBP trial may be considered in the individual patient.

Gabapentin Therapy in Psychiatric Disorders: A Systematic Review.

OBJECTIVE: Gabapentin is commonly used off-label in the treatment of psychiatric disorders with success, failure, and controversy. A systematic review of the literature was performed to elucidate the evidence for clinical benefit of gabapentin in psychiatric disorders. DATA SOURCES: Bibliographic reference searches for gabapentin use in psychiatric disorders were performed in PubMed and Ovid MEDLINE search engines with no language restrictions from January 1, 1983, to October 1, 2014, excluding nonhuman studies. For psychiatric references, the keywords bipolar, depression, anxiety, mood, posttraumatic stress disorder (posttraumatic stress disorder and PTSD), obsessive-compulsive disorder (obsessive-compulsive disorder and OCD), alcohol (abuse, dependence, withdraw), drug (abuse, dependence, withdraw), opioid (abuse, dependence, withdraw), cocaine (abuse, dependence, withdraw), and amphetamine (abuse, dependence, withdraw) were crossed with gabapentin OR neurontin. STUDY SELECTION AND DATA EXTRACTION: The resulting 988 abstracts were read by 2 reviewers; references were excluded if gabapentin was not a study compound or psychiatric symptoms were not studied. The resulting references were subsequently read, reviewed, and analyzed; 219 pertinent to gabapentin use in psychiatric disorders were retained. Only 34 clinical trials investigating psychiatric disorders contained quality of evidence level II-2 or higher. RESULTS: Gabapentin may have benefit for some anxiety disorders, although there are no studies for generalized anxiety disorder. Gabapentin has less likely benefit adjunctively for bipolar disorder. Gabapentin has clearer efficacy for alcohol craving and withdrawal symptoms and may have a role in adjunctive treatment of opioid dependence. There is no clear evidence for gabapentin therapy in depression, PTSD prevention, OCD, or other types of substance abuse. Limitations of available data include variation in dosing between studies, gabapentin as monotherapy or adjunctive treatment, and differing primary outcomes between trials. CONCLUSIONS: Further research is required to better clarify the benefit of gabapentin in psychiatric disorders.