Abstract
Cannabis use is associated with known cardiovascular side effects such as cardiac arrhythmias or even sudden cardiac death. The mechanisms behind these adverse effects are unknown. The aim of the present work was to study the cellular cardiac electrophysiological effects of cannabidiol (CBD) on action potentials and several transmembrane potassium currents, such as the rapid (I(Kr)) and slow (I(Ks)) delayed rectifier, the transient outward (I(to)) and inward rectifier (I(K1)) potassium currents in rabbit and dog cardiac preparations. CBD increased action potential duration (APD) significantly in both rabbit (from 211.7 ± 11.2. to 224.6 ± 11.4 ms, n = 8) and dog (from 215.2 ± 9.0 to 231.7 ± 4.7 ms, n = 6) ventricular papillary muscle at 5 µM concentration. CBD decreased I(Kr), I(Ks) and I(to) (only in dog) significantly with corresponding estimated EC(50) values of 4.9, 3.1 and 5 µM, respectively, without changing I(K1). Although the EC(50) value of CBD was found to be higher than literary C(max) values after CBD smoking and oral intake, our results raise the possibility that potassium channel inhibition by lengthening cardiac repolarization might have a role in the possible proarrhythmic side effects of cannabinoids in situations where CBD metabolism and/or the repolarization reserve is impaired.