A non-selective blocker of voltage-dependent K+-channels (Kv channels) that has greatest potency at Kv1 and Kv3 family members (IC50s = 290, 590, 195, 13, 29, and 100 µM for subunits 1.1, 1.2, 1.3, 1.4, 3.1, and 3.2, respectively); also blocks Kv2 and Kv4 subunits at millimolar concentrations.