Ivabradine is a selective inhibitor of the cardiac pacemaker If current in the sinoatrial node, which reduces heart rate by specifically targeting the hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. In the context of Cluster Headache, it has shown potential in reducing headache frequency and intensity by modulating autonomic nervous system activity and potentially influencing cerebrovascular tone, though its exact mechanism in this indication is not fully elucidated.