A nurse is providing teaching to a client who has angina and a new prescription for sublingual nitroglycerin tablets. Which of the following instructions should the nurse include in the teaching?

A. "Repeat up to four doses until pain is relieved": The typical recommendation for sublingual nitroglycerin is to take one tablet every 5 minutes for up to three doses if the pain persists. If the pain is not relieved after three doses, the client should seek emergency medical help. B. "Store unused tablets at room temperature": Sublingual nitroglycerin should be stored in a tightly closed container at room temperature, away from heat, moisture, and light. This helps maintain the medication's potency. C. "Take two tablets at the onset of pain": The recommended dose of sublingual nitroglycerin is typically one tablet (0.3–0.6 mg) at the onset of angina pain. Taking two tablets at once is not generally advised unless prescribed by a healthcare provider. D. "Take the medication two hours prior to exercise": Nitroglycerin is usually taken at the onset of angina or as prescribed before activities known to trigger angina, but it is not typically taken two hours before exercise. The timing of doses should be based on symptoms, not as a routine preventative measure.