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

Choice A reason: Applying nitroglycerin ointment in a thin, even layer ensures consistent absorption for angina relief, as specified by dosing guidelines (e.g., using a dosing paper). This maximizes efficacy and minimizes side effects like hypotension, aligning with manufacturer instructions, making it the correct teaching point. Choice B reason: Applying to the forearm is not standard, as nitroglycerin ointment is typically applied to the chest, upper arm, or back for optimal absorption. Forearm application may reduce effectiveness due to skin thickness, making this an incorrect site choice. Choice C reason: Applying every 4 hours is incorrect, as nitroglycerin ointment is typically applied 2-3 times daily, with a 12-hour nitrate-free interval to prevent tolerance. This frequency is too frequent and risks side effects, making it an inaccurate instruction. Choice D reason: Massaging nitroglycerin ointment into the skin is contraindicated, as it alters absorption rates and may cause inconsistent dosing or irritation. The ointment is spread lightly and covered, making this instruction incorrect and potentially harmful for proper administration.