: The anticancer drug cisplatin induces cell death by apoptosis. Apoptosis is dependent on cellular loss of potassium ions (K+). We have recently shown that the antifungal drug amphotericin B (enhancing K+ efflux), combined with the Na+, K+, 2Cl−‐cotransport blocker bumetanide (decreasing K+ influx), augmented cisplatin‐induced apoptosis in vitro. We therefore quantified K+ fluxes with the K+ analogue rubidium (86Rb+) in cisplatin‐induced apoptosis of mesothelioma cells treated with bumetanide and amphotericin B. Bumetanide combined with amphotericin B enhanced cisplatin‐induced apoptosis by a pronounced initial reduction of K+ influx due (in addition to Na+, K+, 2Cl−‐cotransport inhibition) also to Na+, K+, ATPase pump inhibition. As 86Rb+ efflux was initially preserved, combination of the drugs would lead to net K+ loss. Combinations of K+ flux modulators leading to cellular potassium ion deprivation thus augments cisplatin‐induced apoptosis and could therefore possibly be used to enhance the antitumour efficacy of cisplatin treatment.