Calcium Channel Blocker Overdose

Most toxic- Toxicity can occur at 2-3 x normal dose in children and the elderly

Rapid absorption

Standard release presentations cause symptoms within 1-2 hours

Beware slow(modified) release preparations as effects can occur up to 12 hours later

They affect myocardial contractility and slow conduction through SAN and AVN.

Antagonize extracellular Ca²⁺ into cardiac muscle
- Affect O phase depolarization in SAN, AVN.
Antagonize extracellular Ca²⁺ Into smooth muscle
- Decreased smooth muscle contraction = vasodilation

How do Patient’s Present?

Decontamination: Activated Charcoal 50g if alert and:

Standard Release
- < 2hours post ingestion
Modified Release
- < 6hours of Amlodipine / Nifedipine / Felodipine / Lercanidipine / Nimodipine
- < 12 hours of Verapamil / Diltiazem

Bradycardia

Hypotension

Fluids: 10-20mL/kg crystalloid- beware as too much fluid can cause pulmonary oedema.
Pressors: Noradrenaline as first line agent, unless bradycardia, then Adrenaline can be used. If using Noradrenaline and not effective can add Vasopressin
Calcium: 30 mL Ca gluconate 10% (3 grams, 6.6 mmol) IV over 10 minutes x 3 in 60 minutes. Then Ca infusion to maintain ionized Ca2+ concentration 1.5 – 2.0 mmol/L
High Dose Insulin Euglycaemic Therapy (Discuss with Toxicology)
- Actrapid 1u/kg IV then infusion +50 ml of 50% dext then infusion
- Sodium Bicarbonate: 1-2 mmol/kg 3-5 min to PH >7.3
Methylene Blue / Lipid Emulsion in refractory shock (Discuss with Toxicology)
ECMO if hypotension is refractory to all treatments