Always check for drug interactions, even with natural remedies, before taking them together. You can check for drug interactions online. You have to be careful with mixing anything with Tramadol since Tramadol works in the brain. When taking it with St. johns wort, Triptophan, or any anti-depressant(I think neurontin too), it can cause serotonin syndrome which is a very serious reaction and can also be life threatening. Some doctor's say it's okay to take these together, but always check with your doctor first and be aware of the symptoms of serotonin syndrome.
Hee is a site you can go to to check for interactions: