Potassium chloride poisoning can be potentially life-threatening, particularly in massive ingestions of sustained-release preparations. Profound hyperkalaemia, developing over several hours, can lead to cardiac arrhythmias and death. This case series reports three episodes of sustained-release potassium chloride poisoning in two individuals requiring whole bowel irrigation or haemodialysis. The first two episodes, in the same patient, illustrate the contrast between the successful use of decontamination versus the need for haemodialysis. The second case, in a child, illustrates the need for tertiary level paediatric expertise in managing this type of poisoning. Whole bowel irrigation with polyethylene glycol is a resource-intensive procedure most beneficial when large numbers of radio-opaque tablets are seen in the stomach. In cases where most of the tablet matter has already been absorbed, extracorporeal methods of rapidly reducing the total body burden of potassium, such as haemodialysis, might be life-saving.