Which antidote is used for calcium channel blocker overdose?

In cases of calcium channel blocker overdose, intravenous calcium is utilized as the antidote because it directly counteracts the effects of the overdose. Calcium channel blockers inhibit the entry of calcium into cells, which is crucial for many physiological processes, including the conduction of electrical impulses in the heart and the contraction of smooth muscles. Administering intravenous calcium helps to restore calcium levels and can improve cardiac contractility and conduction, which are often compromised during an overdose.

Activated charcoal, while useful in many poisoning cases for reducing absorption of the drug, is not a specific antidote and does not reverse the physiological effects of calcium channel blockers. Atropine, primarily used to treat bradycardia, does not address the underlying issues caused by calcium channel blocker toxicity. Deferoxamine is an iron-chelating agent used for iron overload and does not have a role in treating calcium channel blocker overdose. Thus, the use of intravenous calcium specifically targets the symptoms and complications associated with calcium channel blocker toxicity, making it the appropriate answer.