PDE4A and Hypokalemia: This rapid onset suggests that the hypokalemia induced by PAN-selective PDE4 inhibition is likely caused by a transcellular shift of potassium from the vessel lumen into cells, rather than resulting from a loss of serum potassium via the kidneys (reduced reuptake) or digestive system (diarrhea), which occur at a slower pace and are associated with the loss of other electrolytes.