Glucagon and calcium are antidotes for beta and calcium channel blocking (CCB) drug poisoning respectively. A trial of glucagon is probably warranted particularly if the patient has known ischaemic heart disease or other indication for being prescribed these drugs. Calcium will reverse CCB poisoning but may exacerbate a number of other poisonings. Its use is not recommended unless the diagnosis is probable.
After normal supportive care intravenous calcium is considered to be first line treatment for toxicity of calcium channel blockers. In practice these are predominately patients who have taken verapamil or diltiazem.
The patient should initially be given 10 mL of 10% calcium gluconate or calcium chloride (1 gram) and this can then be followed by a further gram every 3 to 5 minutes if there is no response in blood pressure or pulse rate. Large doses may be required (up to 10 grams as initial treatment and 30 grams in total). Calcium chloride produces a higher concentration of calcium than calcium gluconate but should be administered by a central line. Calcium gluconate can be given peripherally.
Patients who respond to repeated bolus generally require continuous infusion.
Serum calcium should be measured, hypercalcaemia is the aim of treatment. A doubling of serum calcium was associated with significant haemodynamic improvement in animals and in humans. An ionised serum calcium of 2 mmol/L was effective in severe nifedipine toxicity and has been suggested as a target concentration.
The treatment of hypotension without heart block should not usually require calcium or any cardioactive medication. It is possible that calcium will be cardiotoxic in patients in this situation (particularly those who have ingested dihydropyridines (e.g. nifedipine)) and may induce ventricular arrhythmias. Hypotension alone should initially be treated with volume expansion and pressor agents