carbamazepine will decrease effectiveness of most drugs , but not tramadol and codeine and dxm
tramadol need to be converted to desmetramadol to be able to agonist mu-opiates receptors which done using cpy2d6 enzyme
tramadol it self is very very weak functional agonist on mu
"Co-administration of quinidine, a potent CYP2D6 enzyme inhibitor, with tramadol, a combination which results in markedly reduced levels of desmetramadol" so the opposite is the opposite
en.wikipedia.org
as for the ability of carbamazepine to induce cpy2d6 i don't know , but you said that , if its significantly true, it will works
@negrogesic sorry i know you was trying to help, but i wasn't able to stop my self from correcting you