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: Applying a new transdermal patch when chest pain is experienced is not a correct instruction, as it may delay the relief of the pain and increase the risk of adverse effects. Transdermal nitroglycerin is a long-acting form of nitrate that is used for the prevention of angina attacks, not for the treatment of acute episodes. The client should use a short-acting form of nitrate, such as sublingual or spray, for the immediate relief of chest pain.

Choice B reason: Applying the transdermal patch in the morning is a correct instruction, as it helps to maintain a steady level of nitrate in the blood throughout the day and prevent angina attacks. Transdermal nitroglycerin has a duration of action of about 12 to 24 hours, depending on the dose and the individual response. The client should apply the patch in the morning and remove it at night, to allow a nitrate-free interval of at least 8 hours and prevent the development of tolerance.

Choice C reason: Applying the transdermal patch in the same location as the previous patch is not a correct instruction, as it may cause skin irritation and reduce the absorption of the medication. Transdermal nitroglycerin should be applied to a clean, dry, and hairless area of the skin, preferably on the chest, upper arm, or back. The client should rotate the application sites and avoid areas that are exposed to heat, moisture, or friction.

Choice D reason: Applying a new transdermal patch once a week is not a correct instruction, as it may not provide adequate protection against angina attacks and increase the risk of rebound angina. Transdermal nitroglycerin should be applied daily, with a nitrate-free interval of at least 8 hours, to maintain a therapeutic level of nitrate in the blood and prevent the loss of efficacy. The client should follow the prescribed dosing schedule and consult the provider before making any changes.

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.