The effects of the toxin SXN482 on Ca²⁺ channel currents (I_Ca), Na⁺ currents (I_Na), and K⁺ currents (I_K) have been studied in bovine adrenal medullary chromaffin cells voltage-clamped at −80 mV. Currents were elicited by depolarising pulses to 0–10 mV (I_Ca and I_Na) or to +60 mV (I_K). SNX482 blocked I_Ca in a concentration-dependent manner. The inhibition curve exhibited two phases. The first high-affinity phase comprised 28% of the whole-cell current and exhibited an IC₅₀ of 30.2 nM. The second low-affinity phase comprised over 70% of I_Ca and had an IC₅₀ of 758.6 nM. Blockade was rapid and fully reversible upon washout of the toxin. Occlusion experiments showed additivity of blockade exerted by nifedipine plus SNX482 (0.3 μM) and by ω-conotoxin GVIA plus SNX482. In contrast, blockade exerted by combined ω-agatoxin IVA plus SNX482 (about 50% of the whole cell) did not show additivity. At 0.3 μM and higher concentrations, SNX482 delayed the inactivation of I_Na. The time constant (τ) for inactivation of I_Na in control conditions doubled in the presence of 0.5 μM SNX482. At 0.3 μM, SNX482 did not affect I_K. Our data demonstrate that: (i) SNX482 selectively blocks P/Q Ca²⁺ channels at submicromolar concentrations; (ii) the toxin partially blocks Na⁺ channels; (iii) SNX482 delays the inactivation of Na⁺ channels. These results reveal novel properties of SNX482 and cast doubts on the claimed selectivity and specificity of the toxin to block the R-type Ca²⁺ channel.