The potassium-sparing diuretics are competitive antagonists that either compete with aldosterone for intracellular cytoplasmic receptor sites, or directly block sodium channels (specifically epithelial sodium channels (ENaC) by amiloride ). The former prevents the production of proteins that are normally synthesized in reaction to aldosterone. These mediator proteins are not produced, and so stimulation of sodium-potassium exchange sites in the collection tubule does not occur. This prevents sodium re-absorption and potassium and hydrogen ion secretion. 
Occlusive therapy is highly effective. Apply the topical steroids mentioned above under subacute eczema and cover with a plastic wrap such as Saran wrap. The plastic dressing does not have to be airtight. Secure the dressing with tape on either end. A sock will hold the plastic dressing against a foot. The dressing may stay on for 2 hours or overnight. Remove the dressing and apply an emollient or more medication. It is not necessary to wash the skin each time a plastic dressing is applied. The appearance of pustules indicates a secondary infection. Stop treatment and prescribe topical or oral antibiotics for this side effect of occlusive therapy.