A nurse in the emergency department is caring for a client who took 3 nitroglycerin tablets sublingually for chest pain. The client reports relief from the chest pain but now he is experiencing a headache. Which of the following statements should the nurse make?

A. A headache is not an allergic reaction to nitroglycerin. It is a common side effect caused by the vasodilation that the medication induces, which can cause tension in the head. B. A headache is a well-known side effect of nitroglycerin due to its action of dilating blood vessels. The medication is effective in relieving chest pain but can also cause vasodilation in other areas, including the head, leading to a headache. C. A headache is not an indication of tolerance. Tolerance to nitroglycerin occurs when the medication becomes less effective over time, usually with prolonged use, but it does not typically cause headaches. D. Headaches are not caused by anxiety but are a direct side effect of nitroglycerin use, which relaxes blood vessels throughout the body, including the head.