Calcium gluconate
Zeltacin · Calcium Gluconate B. Braun
First-line intervention in hyperkalaemia with ECG changes: calcium restores the margin between resting membrane potential and threshold potential and protects the myocardium against arrhythmia within minutes — but does not lower potassium by a tenth of a millimole. Insulin-glucose, beta-agonists, and dialysis must be started in parallel, otherwise the arrhythmia risk returns when the calcium effect wanes after half an hour. Calcium gluconate contains approximately one third as much elemental calcium per ml as calcium chloride, and that confusion is the most common dosing error in acute calcium treatment.
10 ml calcium gluconate 100 mg/ml provides approximately 2,25 mmol calcium, whereas 10 ml calcium chloride 100 mg/ml provides approximately 6,8 mmol — the same volume, three times the dose. Never give calcium through the same line as sodium bicarbonate or phosphate-containing solutions without intervening flushing; precipitation of calcium carbonate or calcium phosphate respectively can block the line and cause embolisation.
Dosing in adults
| Indication | Regimen | Comment |
|---|---|---|
| Hyperkalaemia with ECG changes | 10 ml calcium gluconate 100 mg/ml (≈ 2,25 mmol) iv over 2–3 minutes; repeat after 5–10 minutes if ECG does not normalise | does not lower potassium — start insulin-glucose simultaneously |
| Symptomatic hypocalcaemia (tetany, laryngospasm, seizures) | 10–20 ml 100 mg/ml diluted in 50–100 ml glucose 50 mg/ml iv over 10 minutes, then infusion 0,5–1,5 mmol/h until symptom-free | correct magnesium in parallel, otherwise the hypocalcaemia responds poorly |
| Calcium channel blocker intoxication | 20–30 ml 100 mg/ml iv over 5–30 minutes, repeated as needed; aim for ionised calcium around 1,5 mmol/l | combined with high-dose insulin-euglycaemia; contact the Poison Information Centre |
| Magnesium intoxication (areflexia, respiratory depression) | 10 ml 100 mg/ml (≈ 2,25 mmol) iv over 2–3 minutes, repeat if symptoms persist | stop the magnesium infusion simultaneously |
| Citrate-induced hypocalcaemia during massive transfusion | 10 ml 100 mg/ml iv per 2–4 red cell units, guided by ionised calcium | do not give through the same line as the blood product |
No dose reduction for acute indications — calcium is guided by clinical effect and ionised calcium, not by eGFR. In chronic renal failure there is risk of hypercalcaemia and vascular calcification with repeated administration, particularly with concurrently elevated phosphate; monitor calcium and phosphate levels before continuing supplementation.
No dose adjustment. In severe hepatic failure, citrate metabolism is impaired, which increases calcium requirements during citrate-anticoagulated dialysis and massive transfusion.
Hyperkalaemia and symptomatic hypocalcaemia: 0,5 ml/kg calcium gluconate 100 mg/ml (≈ 0,11 mmol/kg) iv over 5–10 minutes, maximum 20 ml per dose. Must be diluted and given slowly under ECG monitoring.
Do not stop at calcium when potassium is high: the membrane stabilisation buys 30–60 minutes, and if no potassium-lowering treatment is started in that window the arrhythmia risk returns without warning. Also avoid calcium as a reflex treatment for digoxin toxicity with hyperkalaemia — there the potassium is a marker of inhibited sodium-potassium pump, and what should be given is digoxin antibody fragments.
Pharmacokinetics
- ONSET
- 1–3 minutes iv
- EFFECT DURATION
- 30–60 minutes after bolus
- CALCIUM CONTENT
- 100 mg/ml ≈ 0,225 mmol Ca/ml (≈ 9 mg/ml)
- COMPARISON
- calcium chloride 100 mg/ml ≈ 0,68 mmol Ca/ml — three times more
- PROTEIN BINDING
- approximately 45 % of total calcium, mainly to albumin
- EXCRETION
- Renal with marked tubular reabsorption; deposition in bone
- NORMAL VALUE
- ionised calcium 1,15–1,35 mmol/l
- CONVERSION
- 1 mmol Ca = 40 mg = 2 mEq