Kynurenine pathway dysregulation in attention-deficit hyperactivity disorder: Impact on N-methyl-D-aspartate receptors and phasic dopamine maturation

Table 2 Comparative mechanisms of attention-deficit/hyperactivity disorder pharmacotherapy

Feature	Methylphenidate	KMO inhibitors
Primary target	Dopamine/norepinephrine transporters	KMO enzyme
Mechanism	Increases synaptic catecholamines	Blocks neurotoxic branch; raises KYNA
Circuit impact	Direct enhancement of reward signaling	Reduction of metabolic “noise” and excitotoxicity
Side effect profile	Potential appetite/sleep disruption	Targeted metabolic shift (lower systemic risk)
Role in kynurenine pathway	Indirect stabilizer (increases KYNA)	Direct pathway modulator

KMO: Kynurenine 3-monooxygenase; KYNA: Kynurenic acid.