Calcium Channel Blockers Flashcards
List commonly used CCBs.
Amlodipine, diltiazem, felodipine, lercanidipine, nifedipine, nimodipine and verapamil.
What are the non-dihydropyridines and the dihydropyridines?
Non: verapamil/diltiazem (= cardiac > vasodilatation), Dihydro: rest (= vasodilatation > cardiac effects)
Describe the clinical picture for a patient with a verapamil or diltiazem overdose.
Cardiovascular collapse 4-16 hours post-ingestion of XR preparations.
What is the minimum dose that may cause severe toxicity with verapamil or diltiazem overdose?
With XR preparations 2-3 times normal therapeutic dose can sometimes cause severe cardiac collapse in susceptible individuals. This equates to >10 tablets.
Other than verapamil and diltiazem, overdose of the other CCBs usually results in what clinical picture?
Bradycardia, hypotension but not usually lethal/toxic
What must you know about CCB overdose in children?
Ingestion of >2 tablets of XR verapamil/diltiazem in children is potentially lethal
How do the CCBs work?
Prevent the opening of L-type calcium channels, resulting in decreased calcium influx. Leads to vascular smooth muscle relaxation, slowing of cardiac conduction and reduced cardiac contraction force. Non-dihydros (verapamil/diltiazem) = cardiac > peripheral vasodilatation. Dihydros the opposite.
How do CCBs result in hypotension?
Peripheral vasodilatation, bradycardia and decreased contractility
What are two metabolic side effects with CCB overdose?
Hyperglycaemia and lactic acidosis
Describe the pharmacokinetics for CCBs.
Well absorbed, high VoD, protein bound, undergo hepatic metabolism (high first pass, bioavailability of 40%). Bioavailability may increase in overdose.
List the clinical features of CCB overdose.
Cardiac: brady, hypotension, shock, AMI, stroke, non-occlusive mesenteric ischaemia. CNS: seizures, coma (rare, usually with co-ingestants). Metabolic: lactic acidosis, hyperglycaemia
When should high-dose insulin therapy be initiated in CCB overdose?
Hypotension (SBP <90) refractory to fluid resus
Describe your management of acute CCB intoxication.
Two large-bore IVs, fluid resuscitation. Early echo to help guide initial management. Early invasive BP monitoring. Commence high-dose insulin therapy, calcium (x3), knowledge catecholamines are rarely effective in isolation, ventricular pacing to bypass AV blocks (<60 bpm), cardiopulmonary bypass, ECMO, IABP, albumin dialysis. Consider activated charcoal for patients presenting within 1-4 hours and intubated patients. Consider whole bowel irrigation.
When should high-dose insulin therapy be initiated in CCB overdose?
Hypotension (SBP <90) refractory to fluid resus
What drugs would you use to induce a patient with CCB intoxication?
Ketamine, fentanyl, roc or vecuronium
