A nurse administered nitroglycerin sublingually to a client who has angina pectoris and experienced chest pain. The client states that his chest pain is relieved but now he has a headache. Which of the following responses by the nurse is appropriate?

"A headache is a common adverse effect of this medication, but it will probably occur less often over time.

"It sounds as if you are allergic to this medication."

"Your headache is probably a result of anxiety about the chest pain."

"A headache indicates tolerance to the medication."