It is a highly selective blocker of the high conductance Ca²⁺-activated K⁺ channel. Iberiotoxin appears to modulate ChTX binding by an allosteric mechanism.

As a specific blocker of Ca²⁺-activated K⁺ channels, Iberiotoxin does not affect other types of voltage-dependent K⁺ channels which are sensitive to inhibition by Charybdotoxin. Iberiotoxin blocks Ca²⁺-activated K⁺ channels by binding to their external mouth, and this binding is tighter and with an equilibrium dissociation constant 10-fold lower than that of Charybdotoxin.

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