The healthcare provider prescribes the anticoagulant heparin for a client with a pulmonary embolism. Before initiating the medication, the nurse should ensure that which drug is readily available in case of heparin overdose?

A. Warfarin: Warfarin is an oral anticoagulant used for long-term anticoagulation, but it is not used for reversing the effects of heparin. They are different classes of anticoagulants with distinct reversal agents. B. Vitamin K: Vitamin K is used to reverse the effects of warfarin, not heparin. C. Protamine sulfate: Protamine sulfate is the specific antidote for heparin overdose. It neutralizes the effects of heparin and is used to quickly reverse its anticoagulant effects in case of an overdose or excessive bleeding. D. Diphenhydramine HCl: Diphenhydramine is an antihistamine and has no role in reversing anticoagulants.