Calcium chloride is a salt made of calcium and chlorine. In medicine, it is used to treat hypocalcemia by mixing it in solution with water and injecting it intravenously. It can also be used to treat magnesium toxicity and to protect the myocardium from high levels of potassium. It can also be used to treat overdoses of calcium channel blockers.

In Last Temptation, Martha M. Masters uses the fact that calcium chloride can increase the speed of clotting first to suggest to Dr. Ron Simpson that he use it during an operation and later to use it as an antidote when she doses Kendall Pearson to get her parents to consent to the amputation of her cancerous arm.

Calcium chloride at Wikipedia