Potent selective inhibitor of high conductance (maxi-K), different medium and small conductance calcium-activated potassium channels (KCa1.1/KCNMA1 and others), as well as a voltage-dependent potassium channel (Kv1.3/KCNA3>Kv1.2/KCNA2>Kv1.6/KCNA3>>Shaker/Sh). It blocks channel activity by a simple bimolecular inhibition process