My cat was prescribed both Tramadol
for chronic pain, anxiety, and depression (Gabapentin has mild mood stabilizing effects and helps with nerve pain, Tramadol has an SNRI/SSRI
effect and hits a few opiate
receptors). He has since stopped using both drugs
The combination of Tramadol and Gabapentin alone is actually pretty safe, as Tramadol lowers the seizure threshold, and Gabapentin raises it. However, the amount of Gabapentin you're taking has a reasonable chance of causing deafness/tinnitus that may or may not be temporary, as it is considered ototoxic (toxic to the ear).
Now, since Gabapentin raises the seizure threshold, it has probably kept you from having any neurological issues. Ritalin
BOTH lower the seizure threshold, add some Tramadol to that - especially anything over 50mg - and you're potentially negating Gabapentins threshold raising effects and putting yourself at risk for an "absence" or petite mal seizure in the least. Worst case could be a tonic-clonic seizure, which can kill you.
As a side note, Gabapentin by itself (no alcohol or anything else combined with it) is almost impossible to overdose on and its CNS depression is extremely negligible, just keep your doses under 2 grams and watch out for tinnitus.
My cat has had a lot of fun combining drugs, but please be safe doing so.
I would post links to support all of this, but there is a 50-post minimum before links can be posted. Google searches will net you the studies supporting any of the above info.