Cilobradine is an Hyperpolarization-activated cyclic nucleotide-gated (HCN) channel blocker patented by a pharmaceutical company Boehringer Ingelheim G.m.b.H. for sinus tachycardia treatment. In clinical trials Cilobradine decrease Heart rate. Chronically increased heart rate (HR) is a risk factor for mortality and morbidity with adverse consequences on vascular function, atherogenesis, myocardial ischemia, myocardial energetics and left the ventricular function. Heart rate response was found to be concentration-dependent and appeared with a significant delay with respect to the time course of cilobradine in plasma.