Toxic Syndromes: Calcium Channel Blockers

CALCIUM CHANNEL BLOCKERS

Calcium antagonists can cause serious toxicity or death with rela-tively small overdoses. These channel blockers depress sinus node automaticity and slow AV node conduction . They also reduce cardiac output and blood pressure. Serioushypotension is mainly seen with nifedipine and related dihydro-pyridines, but in severe overdose all of the listed cardiovascular effects can occur with any of the calcium channel blockers.

Treatment requires general supportive care. Since most ingested calcium antagonists are in sustained-release form, it may be pos-sible to expel them before they are completely absorbed; initiate whole bowel irrigation and oral activated charcoal as soon as pos-sible, before calcium antagonist-induced ileus intervenes. Calcium, given intravenously in doses of 2–10 g, is a useful antidote for depressed cardiac contractility but less effective for nodal block or peripheral vascular collapse. Other treatments reported to be help-ful in managing hypotension associated with calcium channel blocker poisoning include glucagon and high-dose insulin (0.5–1 unit/kg/h) plus glucose supplementation to maintain eugly-cemia. Recently case reports have suggested benefit from adminis-tration of lipid emulsion (Intralipid, normally used as an intravenous dietary fat supplement) for severe verapamil overdose.