Something I have often wondered. Relatively weak, it would seem.
Perloff MD, Berlin RK, Gillette M, Petersile MJ, Kurowski D. Gabapentin in
Headache Disorders: What Is the Evidence? Pain Med. 2015 Sep 23. doi:
10.1111/pme.12931. [Epub ahead of print]
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.
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.
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.
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.