Zatebradine hydrochloride is a potent HCN channels antagonist. It could decrease the heartbeat in a reversible manner. It is a bradycardic compound that blocks hyperpolarization-activated inward current through cyclic nucleotide-gated cation channels in sinoatrial node cells. It can block voltage-gated outward K+ currents and related neuronal hyperpolarization-activated inward current channels, but exhibits little or no activity for L-type Ca2+ currents. It is also a sinus node inhibitor.?? It displays negative chronotropic activity in isolated guinea pig atria. It was developed by Boehringer Ingelheim.