[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › Electrolytes and rehydration solutions [Pharmacology](https://durgical.com/en/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) ## Key points - Concentrated potassium chloride is never given as an IV push or bolus: it can stop the heart. It is always diluted and given by pump. - Magnesium sulfate toxicity: lost patellar reflexes first, then breathing depression; IV calcium counteracts it. - IV calcium protects the heart in severe hyperkalaemia without lowering potassium. - Calcium precipitates with bicarbonate, phosphate and ceftriaxone in the same line. - Oral rehydration salts with zinc are the WHO treatment for childhood diarrhoea. ## Drugs in this class - [**Calcium gluconate** IV 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)](https://durgical.com/en/pharmacology/calcium-gluconate/) - [**Magnesium sulfate** IV 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)](https://durgical.com/en/pharmacology/magnesium-sulfate/) - [**Oral rehydration salts** A 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](https://durgical.com/en/pharmacology/oral-rehydration-salts/) - [**Potassium chloride** The 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)](https://durgical.com/en/pharmacology/potassium-chloride/) - [**Sodium hydrogen carbonate** Sodium 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)](https://durgical.com/en/pharmacology/sodium-hydrogen-carbonate/) - [**Calcium chloride** IV 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)](https://durgical.com/en/pharmacology/calcium-chloride/) ## 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. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/classes/electrolytes-and-rehydration-solutions/) [← All of pharmacology](https://durgical.com/en/pharmacology/) 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](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=559a0a8c-a8fe-40a5-b196-21f9308780ab) (DailyMed (U.S. National Library of Medicine), 2026); [DailyMed - MAGNESIUM SULFATE- magnesium sulfate heptahydrate injection, solution](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e921a46b-9a5b-4163-9c88-224247541f14) (DailyMed (U.S. National Library of Medicine), 2026); [DailyMed - CALCIUM GLUCONATE injection, solution](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=16307c00-d0d5-4e05-821f-17b0c1a29fc9) (DailyMed (U.S. National Library of Medicine), 2025); [Diarrhoeal disease](https://www.who.int/news-room/fact-sheets/detail/diarrhoeal-disease) (World Health Organization, 2024). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/pharmacology/classes/electrolytes-and-rehydration-solutions/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/classes/electrolytes-and-rehydration-solutions/