Potassium

Potassium

Potassium is the major positively charged ion (cation) in ICF. Be-cause the body can’t store potassium, adequate amounts must be ingested daily. If this isn’t possible, potassium replacement can be accomplished orally or I.V. with potassium salts, such as:

·                 potassium acetate

·                 potassium bicarbonate

·                 potassium chloride

·                 potassium gluconate

·                 potassium phosphate.

Pharmacokinetics (how drugs circulate)

Oral potassium is absorbed readily from the GI tract.

Absorption, metabolism, and excretion

After absorption into the ECF, almost all of the potassium passes into the ICF. There, the enzyme adenosinetriphosphatase main-tains the concentration of potassium by pumping sodium out of the cell in exchange for potassium.

Normal serum levels of potassium are maintained by the kid-neys, which excrete most excess potassium intake. The rest is ex-creted in stool and sweat.

Pharmacodynamics (how drugs act)

Potassium moves quickly into ICF to restore depleted potassium levels and reestablish balance. It’s an essential element in deter-mining cell membrane potential and excitability.

Feel nervous about potassium?

Potassium is necessary for proper functioning of all nerve and muscle cells and for nerve impulse transmission. It’s also essential for tissue growth and repair and for maintenance of acid-base balance.

Pharmacotherapeutics (how drugs are used)

Potassium replacement therapy corrects hypokalemia, low levels of potassium in the blood. Hypokalemia is a common occurrence in conditions that increase potassium excretion or depletion, such as:

·                 vomiting, diarrhea, or nasogastric suction

·                 excessive urination

·                 some kidney diseases

·                 cystic fibrosis

·                 burns

·                 excess of antidiuretic hormone or therapy with a potassium-depleting diuretic

·                 laxative abuse

·                 alkalosis

·                 insufficient potassium intake from starvation, anorexia nervosa, alcoholism, or clay ingestion

·                 administration of a glucocorticoid, I.V. amphotericin B, vitamin B₁₂, folic acid, granulocyte-macrophage colony–stimulating factor, or I.V. solutions that contain insufficient potassium.

Be still my heart

Potassium decreases the toxic effects of digoxin. Because potassi-um inhibits the excitability of the heart, normal potassium levels moderate the action of digoxin, reducing the chances of toxicity.

Drug interactions

Potassium should be used cautiously in patients receiving potassium-sparing diuretics (such as amiloride, spironolactone, and triamterene) or angiotensin-converting enzyme inhibitors (such as captopril, enalapril, and lisinopril) to avoid hyperkal-emia. (See Adverse reactions to potassium.)