From allergy to arrhythmia – electrophysiological basis for the antiarrhythmic properties of antazoline

Introduction Antazoline, a first-generation H 1 -antihistamine, has shown rapid and effective antiarrhythmic action, particularly in recent-onset paroxysmal atrial fibrillation. Despite clinical use in some countries, the underlying electrophysiological mechanisms remain incompletely understood, and concerns about potential proarrhythmic effects persist. Here, we aim to systematically characterize the ion channel interaction profile of antazoline and assess its molecular mode of action. Methods Electrophysiological measurements were performed using the two-electrode voltage clamp technique on 22 cardiac ion channels, expressed in Xenopus laevis oocytes. Results Antazoline strongly inhibited hERG (IC 50 end-pulse: 43.3 µM; peak-tail: 162.6 µM) and hKir3.1/3.4 (IC 50 : 52.8 µM) in a concentration- and state-dependent manner. Block of hERG was attenuated by Y652A and F656A pore mutations, implicating classical aromatic binding residues. Positive rate dependence and open- and inactivated-state as well as partial closed-state inhibition were observed. In contrast, hK 2P 17.1 was significantly activated. Discussion Antazoline exhibits a distinct multichannel profile in a heterologous expression system, combining potent inhibition of hERG and hK ir 3.1/3.4 with activation of hK 2P 17.1. The combined modulation of these channels suggests a potential atrial-preferential electrophysiological profile, while hERG inhibition indicates a need for careful evaluation of ventricular repolarization safety.