For a common example likely to be found in some youth, the combination of an SSRI and a second-generation antipsychotic in long-term concomitant regimens has been shown to produce blockade of P-450 enzymes caused by competitive inhibition of the enzymes (64) and could lead to a serotonin syndrome or to toxic levels of an antipsychotic. Here, CYP2B6 is linked to serotonin syndrome.