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INTRODUCTION

  1. Pharmacology. Potassium is the primary intracellular cation, which is essential for the maintenance of acid-base balance; intracellular tonicity; transmission of nerve impulses; contraction of cardiac, skeletal, and smooth muscle; and maintenance of normal renal function (and ability to alkalinize urine). Potassium also acts as an activator in many enzyme reactions and participates in many physiological processes such as carbohydrate metabolism, protein synthesis, and gastric secretion. Potassium is critical in regulating nerve conduction and muscle contraction, especially in the heart. A variety of toxins cause alterations in serum potassium levels (see Table I-27).

  2. Indications

    1. For treatment or prevention of hypokalemia.

    2. Supplement to bicarbonate therapy (see Bicarbonate, Sodium) for alkalinization of urine.

  3. Contraindications

    1. Potassium should be administered cautiously in patients with renal impairment or impairment of renal excretion of potassium (ACE inhibitor toxicity and hypoaldosteronism, potassium-sparing diuretics) to avoid the potential for serious hyperkalemia.

    2. Potassium should be administered cautiously in patients with impairment of intracellular transport of potassium (due to inhibition of Na-K ATPase pump with cardiac glycosides or inhibition of beta-adrenergic transport with beta-blockers). Administration of potassium may lead to large incremental rises in serum levels.

    3. Potassium should be administered cautiously in patients with intracellular spillage of potassium (rhabdomyolysis, hemolysis).

    4. Potassium should be administered cautiously in patients with severe acute dehydration.

  4. Adverse effects. Hyperkalemia is the most serious adverse reaction.

    1. Nausea, vomiting, abdominal pain, and diarrhea with oral administration.

    2. Parenteral administration. Note: DO NOT use undiluted injectable potassium preparations: direct injection can be lethal if given too rapidly; pain at the injection site and phlebitis may occur, especially during infusion of solutions containing greater than 30 mEq/L.

    3. Use in pregnancy. FDA Category C (indeterminate) (see Section III).

  5. Drug or laboratory interactions

    1. Drug interactions, see Contraindications, above.

    2. Numerous IV incompatibilities: mannitol, diazepam, dobutamine, ergotamine, fat emulsion, nitroprusside, ondansetron, phenytoin, penicillin G sodium, promethazine, streptomycin.

    3. Serum potassium levels may be fictitiously elevated if the blood sample is hemolyzed.

  6. Dosage and method of administration (adults and children). The dose depends on the serum potassium level and severity of symptoms. Potassium depletion resulting in a 1-mEq/L decrease in serum potassium level may require as much as 100–200 mEq to restore body stores in an adult. However, this does not apply to conditions where the level is low because of an intracellular shift of potassium (eg, methylxanthine or beta-adrenergic agonist toxicity).

    1. For parenteral administration, potassium must be diluted (see Adverse effects, above).

    2. The usual daily adult maintenance dose is 40–80 mEq (children: 2–3 mEq/kg or 40 mEq/m2).

    3. For a serum potassium of 3.0 mEq/L or higher, the oral route is the preferred method of repletion.

    4. Intravenous dosing. Note: Continuous cardiac monitoring with frequent laboratory monitoring is recommended during administration of IV potassium (especially for rates >0.5 mEq/kg/h). Adjust the volume of fluid to the patient's body size.

      1. For a serum potassium between 2.5 mEq/L and 3.0 mEq/L, the maximum IV infusion rate of potassium is 10 mEq/h, the maximum ...

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