No I do not believe any negative interactions would occur by utilizing cannabis along with gabapentin and/or tramadol. Cannabis is a very safe herb, and has been used as medicine for thousands of years. Often times cannabis is a great replacement for synthetic monodrug compounds like tramadol and gabapentin (which can have serious side effects). Cannabis does have a potentiating effect with many compounds, often leading patients to need less of their other pharmaceutical compounds. One study found synthetic THC to be equal to gabapentin in treating neuropathic pain in patients with peripheral neuropathy.
Pain Practice. 2011 Jul-Aug;11(4):353-68. doi: 10.1111/j.1533-2500.2010.00427.x. Epub 2010 Nov 18.
An open-label comparison of nabilone and gabapentin as adjuvant therapy or monotherapy in the management of neuropathic pain in patients with peripheral neuropathy.
I agree with Dr. Vanderveer in that cannabis can be an alternative for either tramadol or gabapentin in the right situations. However, I do not think that was what the question was asking so I respectively disagree with him on this interaction. In my past pain management training, we were taught that cannabis can definitely interact with items like Neurontin/ Gabapentin and Tramadol and increase the risk of fall/ accident risk. In fact, I just saw a complicated pain pt yesterday and had to review safety issues because I highly suspect a recent fall she sustained might've been caused by just this interaction. There is also an official webpage for people devoted to tramadol abuse; the claim is made that cann might even lead to poss. increased Sz risk in those who are heavy tramadol users (however, I'm still researching this claim and am still on the fence about this). So to re-iterate; I completely agree w/ Dr. Vandeveer that cann can possibly be used to replace gabapentin and tramadol for certain pain syndromes. However, I respectively disagree with him about there being no possible negative interactions w/ cann and tramadol &/or gabapentin