Ajmaline is an alkaloid that has been found in R. serpentina and has ion channel inhibitory and antiarrhythmic activities.1,2,3,4,5 It inhibits the human-ether-a-go-go (hERG) potassium channel, also known as Kv11.1, and the voltage-gated potassium channel subtypes Kv1.5 and Kv4.3 with IC50 values of 42.3, 293, and 186 ?M, respectively, in Xenopus oocytes expressing the channels.2,3 Ajmaline (1 ?g/ml) increases the action potential duration in isolated dog atrium and ventricle.4 It increases the functional refractory duration in the atrium, ventricle, and atrioventricular conduction system in anesthetized dogs when administered intravenously at a dose of 1 mg/kg.4 Ajmaline (2 mg/kg, i.v.) reduces the number of premature ventricular complexes and decreases the duration of ventricular tachycardia and ventricular fibrillation in coronary artery-ligated anesthetized rats.5
1.Srivastava, A., Tripathi, A.K., Pandey, R., et al.Quantitative determination of reserpine, ajmaline, and ajmalicine in Rauvolfia serpentina by reversed-phase high-performance liquid chromatographyJ. Chromatogr. Sci.44(9)557-560(2006) 2.Kiesecker, C., Zitron, E., Lück, S., et al.Class Ia anti-arrhythmic drug ajmaline blocks HERG potassium channels: Mode of actionNaunyn-Schmiedebergs Arch. Pharmacol.370(6)423-435(2004) 3.Fischer, F., Vonderlin, N., Zitron, E., et al.Inhibition of cardiac Kv1.5 and Kv4.3 potassium channels by the class Ia anti-arrhythmic ajmaline: Mode of actionNaunyn-Schmiedebergs Arch. Pharmacol.386(11)991-999(2013) 4.Bojorges, R., Pastelin, G., Sanchez-Perez, S., et al.The effects of ajmaline in experimental and clinical arrhythmias and their relation to some electrophysiological parameters of the heartJ. Pharmacol. Exp. Ther.193(1)182-193(1975) 5.Hashimoto, Y., Hori, R., Okumura, K., et al.Pharmacokinetics and antiarrhythmic activity of ajmaline in rats subjected to coronary artery occlusionBr. J. Pharmacol.88(1)71-77(1986)