A nurse is obtaining a medical history from a client who is to start warfarin therapy and currently uses herbal supplements at home. The nurse should inform the client that which of the following herbal supplements can interact adversely with warfarin?

Choice A reason: Atropine is not the correct answer, as it is an anticholinergic medication that is used to treat bradycardia, not warfarin overdose. Atropine has no effect on the INR or the coagulation cascade.

Choice B reason: Epinephrine is not the correct answer, as it is a catecholamine medication that is used to treat anaphylaxis, cardiac arrest, or severe hypotension, not warfarin overdose. Epinephrine has no effect on the INR or the coagulation cascade.

Choice C reason: Vitamin K is the correct answer, as it is the antidote for warfarin overdose. Vitamin K is a fat-soluble vitamin that is essential for the synthesis of clotting factors II, VII, IX, and X. Vitamin K can reverse the effects of warfarin and lower the INR to a therapeutic range.

Choice D reason: Protamine is not the correct answer, as it is the antidote for heparin overdose, not warfarin overdose. Protamine is a protein that binds to and neutralizes heparin, but has no effect on warfarin or the INR.

Choice A reason: A headache is not likely due to the anxiety about the chest pain, as anxiety usually causes other symptoms, such as palpitations, sweating, or trembling. A headache is more likely related to the vasodilating action of nitroglycerin, which causes increased blood flow to the brain.

Choice B reason: A headache does not indicate tolerance to the medication, as tolerance usually manifests as a reduced effect of the medication on relieving chest pain. A headache is more likely a sign of the medication's potency, as it indicates that the nitroglycerin is reaching the systemic circulation.

Choice C reason: A headache is an expected adverse effect of the medication, as nitroglycerin causes vasodilation of the cerebral vessels, which can result in increased intracranial pressure and pain. A headache is usually mild and transient, and can be relieved by taking analgesics, such as acetaminophen.

Choice D reason: A headache is not an indication of an allergy to the medication, as an allergic reaction usually causes other symptoms, such as rash, itching, swelling, or difficulty breathing. A headache is more likely a pharmacological effect of the medication, rather than an immunological response.