D,L N,O-Didesmethyl Venlafaxine is a metabolite of Venlafaxine. Venlafaxine is a derivative of phenylethylamine which is reported to facilitate neurotransmission within the central nervous system via blocking the presynaptic reuptake of neuroamines such as serotonin (5-hydroxytryptamine; 5-HT) and noradrenaline (norepinephrine). Velanfaxine is also reported to be a weak inhibitor of dopamine reuptake. In vitro studies indicate that Venlafaxine does not demonstrate significant activity for muscarinic, histaminergic or α-1 adrenergic receptors. The metabolism of venlafaxine is reported to occur by cytochrome P450 (CYP) enzyme CYP2D6 yielding O-desmethylvenlafaxine. A lesser metabolite, N-desmethylvenlafaxine is produced by CYP3A4.