Pharmacology · Class
Electrolytes and rehydration solutions !
Salts of potassium, calcium, magnesium, sodium and bicarbonate, and oral rehydration salts. Simple medicines, but several are high-alert by vein.
Updated 2026-11-01
What they are
Medicines that replace water and electrolytes or correct acid-base problems: oral rehydration salts, potassium chloride, calcium gluconate and chloride, magnesium sulfate and sodium bicarbonate, plus IV fluids. Concentrated IV forms (potassium chloride, magnesium sulfate, hypertonic saline) are ISMP-style high-alert medicines.
Mechanism of action
Each one supplies the ion that is missing or opposes a dangerous effect: potassium restores the resting membrane potential, calcium stabilises the heart membrane and nerves, magnesium blocks calcium entry at the nerve terminal, bicarbonate buffers acid, and oral rehydration salts use glucose-coupled sodium transport in the gut to pull water back into the body.
Target: Ion balance (no single receptor)
Drugs in this class
- Calcium gluconateIV calcium for acute symptomatic hypocalcaemia. It also protects the heart in severe hyperkalaemia and reverses…Calcium ions: membranes of heart, nerve and muscle (no single receptor)
- Magnesium sulfateIV or IM magnesium to prevent and control eclamptic seizures and to replace low magnesium. A high-alert medicine…Calcium entry at the nerve terminal and NMDA-type channels (no single receptor)
- Oral rehydration saltsA mix of salts and glucose dissolved in clean water that replaces fluid lost in diarrhoea. Cheap and life-saving…Sodium-glucose cotransporter 1 (SGLT1) of the small intestine
- Potassium chlorideThe main potassium supplement, by mouth or diluted IV, for low potassium. Concentrated IV potassium is one of the most…Potassium ions: resting membrane potential of heart, nerve and muscle (no single receptor)
- Sodium hydrogen carbonateSodium bicarbonate: an alkali given IV to correct severe metabolic acidosis and to make the urine alkaline in some…Hydrogen ions: bicarbonate buffer of blood and urine (no receptor)
- Calcium chlorideIV calcium with much more calcium per volume than calcium gluconate, but more irritating to veins. Used for acute…Calcium ions: membranes of heart, nerve and muscle (no single receptor)
Others in the class
- Sodium chloride (isotonic and hypertonic)
- Ringer's lactate
- Glucose solutions
- Potassium phosphate
Test yourself
Think of the answer, then tap the question to see it.
Why must concentrated potassium chloride never be injected undiluted?
A sudden high potassium level in the heart depolarises it and can cause fatal arrhythmia or cardiac arrest.
Which clinical sign first warns of magnesium toxicity?
Loss of the deep tendon (patellar) reflexes, which comes before respiratory depression and heart block.
Which IV calcium interaction can be fatal in newborns?
Ceftriaxone with calcium: calcium-ceftriaxone precipitates formed in the lungs and kidneys.
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 - MAGNESIUM SULFATE- magnesium sulfate heptahydrate injection, solution (DailyMed (U.S. National Library of Medicine), 2026); DailyMed - CALCIUM GLUCONATE injection, solution (DailyMed (U.S. National Library of Medicine), 2025); Diarrhoeal disease (World Health Organization, 2024).
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Representative model, for educational purposes only.