Pharmacology · Electrolytes and rehydration solutions
Potassium chloride !
The main potassium supplement, by mouth or diluted IV, for low potassium. Concentrated IV potassium is one of the most dangerous medicines.
Updated 2026-11-01
Mechanism of action
Potassium is the main ion inside cells. Replacing it restores the normal resting membrane potential of heart, nerve and muscle cells, which corrects weakness, cramps and arrhythmias due to low potassium. The chloride also corrects the chloride loss of hypochloraemic metabolic alkalosis, common with diuretics and vomiting. A sudden rise of potassium around the heart depolarises it and can stop it.
- Potassium chloride replaces potassium lost in urine or stool
- The resting membrane potential returns to normal
- Muscle weakness and arrhythmias of low potassium resolve
- Too fast or concentrated: high potassium can stop the heart
Pharmacokinetics
- Absorption
- Well absorbed by mouth; extended-release forms release it slowly in the gut
- Distribution
- Moves into cells, where most body potassium is held
- Elimination
- Mainly by the kidneys, the rest in stool; the kidney does not conserve potassium well
Indications
- Hypokalaemia, with or without metabolic alkalosis, for example from diuretics or vomiting
- Potassium replacement by vein when oral replacement is not possible
- Low potassium in digitalis toxicity
- Hypokalaemic periodic paralysis
Adverse effects
Common
- Nausea, vomiting, abdominal pain and diarrhoea (oral)
- Pain and phlebitis at the infusion site (IV)
Contraindications
- Hyperkalaemia
- Kidney failure or conditions with potassium retention
- Solid oral forms: slowed passage through the gut (e.g. gastroparesis, anticholinergic drugs)
Key interactions
- Potassium-sparing diuretics (spironolactone, amiloride, triamterene)
- Severe hyperkalaemia; the combination is avoided
- ACE inhibitors, ARBs or eplerenone
- Higher risk of hyperkalaemia
- NSAIDs
- Potassium retention and hyperkalaemia
- Anticholinergic drugs
- Slower gut transit and more gut injury with solid oral potassium
- Digoxin
- A fast fall in potassium during treatment of high potassium can trigger digoxin toxicity
What is monitored
- Serum potassium
- Continuous ECG monitoring during faster IV replacement
- Kidney function and urine output
- Fluid and acid-base balance
- IV site
Administration and safety
- Concentrated potassium chloride is NEVER given as an IV push, bolus or IM injection: it can be instantly fatal. It is always diluted in a larger volume and mixed completely.
- Prefer commercially premixed bags; concentrated vials are removed from wards and stored only in pharmacy or controlled areas.
- Infuse with a programmed pump and an independent double check; never by gravity, and never speed up a late infusion.
- Peripheral infusion can burn: watch the vein; higher concentrations need a central line as local protocol states.
- Oral forms: swallow extended-release tablets whole with a full glass of water and a meal; do not crush or chew.
Nursing care
- Before giving: check serum potassium, kidney function and urine output; report reduced urine output.
- During IV replacement: cardiac monitoring as ordered, check the infusion site often, and stop for pain, swelling or ECG changes.
- Watch for signs of high potassium (peaked T waves, slow pulse, weakness, tingling) and low potassium (cramps, weakness, U waves).
- Check what else raises potassium: potassium-sparing diuretics, ACE inhibitors, ARBs, salt substitutes.
- Teach: take oral potassium with food and water, report black stools, abdominal pain or vomiting.
Pregnancy and breastfeeding
Used when needed to correct low potassium; animal data are lacking, but replacing a missing electrolyte is not expected to harm the fetus.
Test yourself
Think of the answer, then tap the question to see it.
Why is IV potassium chloride a high-alert medicine?
Undiluted or too-fast potassium can cause fatal arrhythmia and cardiac arrest within moments; errors with concentrated vials have killed patients.
Which drug class should not be combined with potassium supplements?
Potassium-sparing diuretics such as spironolactone, amiloride or triamterene, because of the risk of severe hyperkalaemia.
Why are solid oral potassium chloride forms avoided when gut transit is slow?
Potassium chloride sitting in the gut can cause ulcers, bleeding or strictures; slow transit from gastroparesis or anticholinergics raises the risk.
How are extended-release potassium chloride tablets taken safely?
Swallowed whole, not crushed or chewed, with a full glass of water and with a meal, to reduce irritation and injury of the gut.
Related drugs
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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - POTASSIUM CHLORIDE injection, solution, concentrate (DailyMed (U.S. National Library of Medicine), 2026); DailyMed - POTASSIUM CHLORIDE tablet, extended release (DailyMed (U.S. National Library of Medicine), 2026); Potassium Chloride Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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