Electrolyte
Potassium chloride
Also called KCl
Indications
- Hypokalemia when oral replacement is impossible or too slow, especially with arrhythmias, digoxin or weakness
- DKA and HHS: added to fluids once K is below 5.0, and given before insulin when K is below 3.5 (ADA 2024)
- Hypochloremic metabolic alkalosis from vomiting, gastric suction or diuretics, where the chloride matters too
- Maintenance potassium in IV fluids and parenteral nutrition
Dosing
| Where | Dose |
|---|---|
| Unit conversions | KCl: 1 mEq = 75 mg; 20 mEq in 100 mL over 1 h is a typical IV limit |
Mechanism of action
Potassium is the main intracellular cation (about 140 mEq/L inside cells against 3.5–5 outside), pumped in by the Na⁺/K⁺-ATPase; the gradient sets the resting membrane potential through inward-rectifier K⁺ channels. Low extracellular K⁺ reduces K⁺ conductance, so repolarization slows (flat T, U waves) and automaticity rises, while skeletal and smooth muscle weaken. Infused K⁺ restores the extracellular level, then moves into cells; the chloride replaces chloride lost from the gut or kidney, letting the kidney excrete bicarbonate and stop wasting K⁺.
Pharmacology
- Cardiovascular: corrects hypokalemic ECG changes and lowers the risk of PVCs, VT, torsades and digoxin toxicity; a fast rise brings peaked T waves, block, VF or asystole
- Neuromuscular: restores strength; severe hypokalemia causes paralysis, respiratory weakness and rhabdomyolysis
- Renal: hypokalemia impairs urine concentration and raises ammonia production (worse hepatic encephalopathy); replacement reverses both
- Metabolic: dextrose diluents release insulin and blunt the rise, so the label prefers saline
Pharmacokinetics
| Onset | Serum K rises during the infusion, then settles as potassium enters cells |
|---|---|
| Distribution | 98% of body potassium (about 3,500 mEq in 70 kg) is intracellular; infused K enters cells over hours |
| Protein binding | None |
| Metabolism | None; an element |
| Elimination | Kidneys 80–90% (label), secreted in the collecting duct under aldosterone; the rest in stool and sweat |
| Deficit | A fall of 1 mEq/L reflects a loss of about 200–400 mEq (Merck), so repeated doses are usual |
| Organ failure | Kidney failure, oliguria, ACE inhibitors, ARBs, spironolactone, trimethoprim and heparin cut excretion: smaller doses, closer levels |
Chemistry
- Potassium chloride (KCl, MW 74.6), an inorganic salt that dissociates completely, so pKa, lipid solubility and stereochemistry do not apply; 1 g = 13.4 mEq
- Concentrate: 2 mEq/mL, 4,000 mOsm/L, pH 4.0–8.0; must be diluted (label) and stays in pharmacy (Joint Commission)
- Premixed bags in water: 10 mEq/100 mL is 200 mOsm/L, 20 mEq/100 mL 400 and 40 mEq/100 mL about 800 (label)
- Added to a hanging bag it can layer at the bottom and run in as a bolus: mix by inversion or use premixed bags
Adverse effects and cautions
Other electrolyte drugs
Sources
- FDA label: Potassium Chloride Concentrate (Hospira, 2026)
- FDA label: Potassium Chloride in Water (ICU Medical, 2018)
- ADA hyperglycemic crises consensus (2024)
For education and exam preparation only. Follow your institution’s protocols. Typical adult values for study. Follow the order, the label and your institution's protocols.