Poisoning with calcium channel blockers

FIGURE 10-6. Pathophysiologic changes associated with calcium channel blocker poisoning. 

The treatment of overdosage with calcium channel blockers has been reviewed (141) other reports have reviewed poisoning with verapamil (142-144), and other calcium channel blockers (145,146). 

Poisoning and drug overdose with acetaminophen, anticholinesterase insecticides, calcium channel blockers, iron, and tricyclic antidepressants are the focus of the remainder of this chapter because they represent commonly encountered poisonings for which pharmacotherapy is indicated. These agents also were chosen because they represent common examples with different mechanisms of toxicity, and they illustrate the application of general treatment approaches as well as ... 

In 2003, the AAPCC-TESS report documented 9650 people with a toxic exposure to a calcium channel blocker, with 339 patients exhibiting and surviving major toxic effects. Fifty-seven people died. Poison control center reports have shown a steady increase in the number of cases of morbidity and mortality following calcium channel blocker overdosage. 

B. Toxicodynamics Toxicodynamics is a term used to denote the injurious effects of toxins, ie, their pharmacodynamics. A knowledge of toxicodynamics can be useful in the diagnosis and management of poisoning. For example, hypertension and tachycardia are typically seen in overdoses with amphetamines, cocaine, and antimuscarinic drugs. Hypotension with bradycardia occurs with overdoses of calcium channel blockers, beta-blockers, and sedative-hypnotics. Hypotension with tachycardia occurs with tricyclic antidepressants, phenothiazines, and theophylline. Hyperthermia is most frequently a result of overdose of drugs with antimuscarinic actions, the salicylates, or sympathomimetics. Hypothermia is more likely to occur with toxic doses of ethanol and other CNS depressants. Increased respiratory rate is often a feature of... 

C. Calcium antagonist poisoning. Start with doses as described above. High-dose calcium therapy has been reported effective in some oases of severe calcium channel blocker overdose. As much as 12 g of calcium chloride has been given over 2 hours. Administer calcium as multiple boluses (eg, 1 g every 10-20 minutes) or as a continuous infusion (eg, 20-50 mg/kg/h). 

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