Toxicology 7: Calcium Channel Blocker Toxicity Portal
Calcium channel blockers have negative ionotrophic and chronotropic effects, resulting in a depression of the myocardial contractility and decreased heart rate.
Specific Calcium Blocker Overdose Therapy
- Calcium is the best therapy for calcium channel blocker overdose. Calcium chloride is preferred, as it has 3 times more calcium per volume than calcium gluconate. Calcium chloride has 13.6 mEq (1g) in a 10 mL vial, while calcium gluconate has 4.53 mEq in a 10 mL vial. However, calcium chloride is more irritating and should be administered via central venous access if at all possible.1
- Initiate 10 to 20 mL of 10% calcium chloride IV over 10 minutes. If no effects are noted, repeat the dose. Then, proceed with IV infusion at 20 to 50 mg/kg/hour of calcium chloride in NS.2 The goal for plasma calcium is 12 to 13 mEq/L. Check the level at 30 minutes after initiation, then every 2 hours.1
- Administer calcium gluconate via peripheral or central venous access. If calcium gluconate is used, adjust the dose to 30 to 60 mL of 10% calcium gluconate.2
- Epinephrine may sensitize the vascularity to calcium effect and make the patient who initially is refractory to medication have response to additional calcium chloride. Therefore, give an initial dose of 10 to 20 mL calcium chloride followed by an epinephrine infusion of 2 to 100 µg/min IV or a combination of epinephrine and dopamine drips. Repeat calcium dose. Give 10 to 20 mL of 10% calcium chloride.
- Atropine may be used to treat bradycardia due to calcium channel blocker overdose. Atropine blocks vagal nerve outflow, decreasing its inhibition of heart rate and cardiac output, and 29% of patients have beneficial response.1 The dose range is 0.5 to 1 mg IV initially to 3 mg total in adults. TCP or TVP may be tried to treat bradycardia, but drug therapy is preferred.
- Hypotension that does not respond to epinephrine infusion may respond to a combination of epinephrine plus dopamine.
- Glucagon increases intracellular cAMP, which increases intracellular calcium concentration, and as a result, increases cardiac and smooth muscle contractility. Treat unresponsive patients with glucagon 3 mg (0.05 mg/kg) IV bolus. Use 5 mg/hour (0.07 mg/kg/hour) IV bolus. Then, titrate to maximum of 10 mg /hour (parameter blood pressure, heart rate, or both).
- Vasopressors may be needed.
- Dopamine at 5 to 20 µg/kg/min. However, dopamine frequently will not sustain blood pressure alone.
- Norepinephrine is frequently added in a dose of 0.5 to 30 µg/kg/min. Isoproterenol may be considered in refractory cases. Dose range is 2 to 10 µg/kg/min.
- Insulin is currently used when symptoms are refractory to other treatments. The recommended starting dose is 0.5 U/kg/hour for IV infusion. Effects are not usually seen until 1 U/kg/hour. As high 10 U/kg/hour has been used. Some clinicians start with 10 U IV push before infusion.
- Give oxygen to all patients.
- Give NS bolus of 500 to 1000 mL along with the initial calcium chloride for treatment.
References
- Harris CR. The Toxicology Handbook for Clinicians. Philadelphia, Pa: Mosby Elsevier, 2006.
- Kerns W, Kline J, Ford MD. B-blocker and calcium channel blocker toxicity. Emerg Med Clin North Am. 1994;12:365.