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

Choice A reason: Anxiety can trigger tension headaches by increasing muscle tension and cortisol release, which may constrict cerebral blood vessels, causing pain. However, nitroglycerin’s vasodilatory effect directly impacts cerebral vessels, increasing blood flow and stretching vessel walls, making it the primary cause of headaches in this context, not anxiety. Choice B reason: Tolerance to nitroglycerin develops with chronic use, reducing its effectiveness for angina relief over time. Headaches are not a symptom of tolerance but result from immediate vasodilation of cerebral blood vessels, which increases intracranial pressure and stimulates pain receptors, a common pharmacological effect unrelated to tolerance development. Choice C reason: Nitroglycerin, a nitrate, relaxes vascular smooth muscle, causing vasodilation. In cerebral vessels, this increases blood flow, stretching vessel walls and activating nociceptive nerve endings, leading to headaches. This is a well-documented side effect, occurring in up to 50% of patients due to the drug’s direct action on vascular tissue. Choice D reason: Allergic reactions to nitroglycerin involve immune-mediated responses, such as rash, itching, or anaphylaxis, driven by histamine release or immunoglobulin E activation. Headaches are not an allergic symptom but a pharmacological effect of vasodilation, causing increased cerebral blood flow and vessel wall tension, distinct from immune-related symptoms.