Due to its serotonergic activity, coadministration of
tramadol with serotonin-enhancing drugs such as SSRIs, SNRIs, nefazodone, trazodone, and mirtazapine may potentiate the risk of serotonin syndrome, which is a rare but serious and potentially fatal condition thought to result from hyperstimulation of brainstem 5-HT1A and 2A receptors.