Duloxetine is a serotonin-norepinephrine reuptake inhibitor (SNRI) that modulates neurotransmitter levels in the central nervous system, potentially reducing pain perception and neurogenic inflammation associated with Cluster Headache. By increasing the synaptic concentrations of serotonin and norepinephrine, it may help interrupt the neurological mechanisms underlying the severe pain and autonomic symptoms characteristic of this condition.