Calcium Channel Blocker Overdose

Calcium‑channel blocker (CCB) overdose - Emergency department guide

Scope and key points

• CCB overdose can cause life‑threatening cardiovascular collapse.
• Verapamil and diltiazem (non‑dihydropyridines) commonly produce profound myocardial depression and conduction block.
• Dihydropyridines (amlodipine, nifedipine) primarily cause vasodilatation but at large overdoses any CCB may depress cardiac function.
• Management is time‑critical: follow standard resuscitation priorities while initiating toxin‑directed therapies early.
• Use TOXBASE/NPIS for agent‑specific guidance and consider early specialist toxicology and critical care involvement.
• Early discussion with an ECMO centre is advised for refractory shock.

Pathophysiology (concise)

• CCBs block L‑type calcium channels in cardiac myocytes, vascular smooth muscle and pancreatic beta cells, causing:
• Negative inotropy and chronotropy, and slowed AV conduction.
• Peripheral vasodilatation and hypotension.
• Inhibition of insulin release → marked hyperglycaemia and impaired myocardial glucose uptake.
• Downstream effects include tissue hypoperfusion, lactic acidosis, acute kidney injury, pancreatitis and rhabdomyolysis.
• Hyperglycaemia and raised lactate are common markers of severity.

Clinical features to recognise