CLINICAL PHARMACOLOGY: Potassium ion is the principal intracellular cation of most body tissues. Potassium ions participate in many essential physiological processes, such as the maintenance of intracellular tonicity, nerve impulse transmission, enzymatic reactions in intermediary metabolism, cardiac, skeletal and smooth muscle function, and the maintenance of normal renal function.
Potassium depletion may occur whenever the rate of potassium loss through renal excretion and/or loss from the gastrointestinal tract exceeds the rate of potassium intake. Potassium depletion usually develops slowly as a result of lengthy therapy with oral diuretics, primary or secondary hyperaldosteronism, diabetic ketoacidosis, or inadequate replacement of potassium in patients on prolonged parenteral nutrition. Depletion is additionally associated with severe diarrhea, accompanied by vomiting. Potassium depletion due to these causes is usually accompanied by a concomitant loss of chloride and is manifested by hypokalemia and metabolic alkalosis. Potassium depletion may result in fatigue, weakness, nausea, drowsiness, loss of appetite, edema, oliguria and chronic ileus with distention. Potassium deficiency may be manifested by shallow breathing, lowered blood pressure, disturbances of cardiac rhythm (primarily ectopic beats), prominent U-waves in the electrocardiogram, or other ECG changes, such as lengthened Q-T interval, depressed S-T segment, and depressed or inverted T-wave. In advanced cases of potassium deficiency, flaccid paralysis and/or impaired ability to concentrate urine may be evident.