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  1. Pharmacology. Potassium is the primary intracellular cation. It is essential for the maintenance of acid-base balance and 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 functions as an activator in many enzyme reactions and participates in many physiologic 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 (See Diagnosis of Poisoning).

    2. As a supplement to bicarbonate therapy (See Bicarbonate, Sodium) for alkalinization of urine.

  3. Contraindications

    1. Potassium should be administered cautiously in patients with renal insufficiency or with impairment of renal excretion of potassium (eg, angiotensin-converting enzyme [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 the 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

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

    2. Parenteral administration. Note: Undiluted injectable potassium preparations should not be used; direct injection can be lethal if given too rapidly, and pain at the injection site and phlebitis may occur, especially during infusion of solutions containing more than 30 mEq/L.

    3. Hyperkalemia is the most serious adverse reaction (See Diagnosis of Poisoning).

    4. Use in pregnancy. FDA Category C (indeterminate [See Introduction in 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 factitiously elevated if the blood sample is hemolyzed.

  6. Dosage and method of administration (adults and children)

    1. The dose is variable and depends on the serum potassium level and severity of symptoms. The normal serum potassium level is 3.5–5 mEq/L. For parenteral administration, potassium must be diluted (see “Adverse Effects” above).

    2. The usual daily adult maintenance dose is 40–80 mEq. The usual daily pediatric maintenance dose is 2–3 mEq/kg or 40 mEq/m2.

    3. Potassium depletion resulting in a 1-mEq/L decrease in serum potassium may require 100–200 mEq for replacement to restore body stores. This replacement requirement will be offset with changes or corrections in intracellular transport (reversal of methylxanthine or beta-adrenergic agonist toxicity).

    4. For a serum potassium level of 2.5 mEq/L or greater, the maximum infusion rate of potassium in adults is 10 mEq/h, maximum concentration is 40 mEq/L, and maximum dose is 200 mEq/24 h. Do not exceed 1 mEq/kg/h or 30 mEq per dose for IV ...

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