“Clinical studies have shown that the major psychoactive ingredient of Cannabis sativa Δ9-tetrahydrocannabinol (THC) has some analgesic efficacy in neuropathic pain states.

However, THC has a significant side effect profile. We examined whether the profile of THC could be improved by co-administering it with the first-line neuropathic pain medication gabapentin.

These findings indicate that gabapentin synergistically enhances the anti-allodynic actions of THC and improves its therapeutic window.

Thus, THC may represent a potential adjuvant for neuropathic pain medications such as gabapentin.”

https://www.ncbi.nlm.nih.gov/pubmed/30312630

https://www.sciencedirect.com/science/article/pii/S0028390818307779?via%3Dihub