Pharmacological and Parenteral Therapies Q 90
A clinic patient has recently been prescribed nitroglycerin for treatment of angina. He calls the nurse complaining of frequent headaches. Which of the following responses to the patient is correct?
A. "Stop taking the nitroglycerin and see if the headaches improve."
B. "Go to the emergency department to be checked because nitroglycerin can cause bleeding in the brain."
C. "Headaches are a frequent side effect of nitroglycerine because it causes vasodilation."
D. "The headaches are unlikely to be related to the nitroglycerin, so you should see your doctor for further investigation."
Correct Answer: C. “Headaches are a frequent side effect of nitroglycerine because it causes vasodilation.”
Nitroglycerin is a potent vasodilator and often produces unwanted effects such as headache, dizziness, and hypotension. Headaches can be severe, throbbing, and persistent and may occur immediately after use. Many of these adverse effects are secondary to the hypotensive effects of nitroglycerin. Patients may report symptoms of orthostatic hypotension which manifest as dizziness, weakness, palpitations, and vertigo. Profound hypotension may occur in patients with preload-dependent conditions.
Option A: Patients should be counseled, and the dose titrated, to minimize these effects. The patient should not stop the medication. No currently known antagonist is available to counteract the effect of nitroglycerin. Since the effects are related to venodilation and relative arterial hypovolemia, efforts to increase central fluid volume have proven to be effective.
Option B: Nitroglycerine does not cause bleeding in the brain. Some patients can be more sensitive to the hypotension caused by nitrates, which can result in nausea, vomiting, diaphoresis, pallor, and collapse even at therapeutic doses.
Option D: Headaches are one of the unwanted side effects of nitroglycerin. Syncope is the most dangerous adverse effect and can result in falls and their resultant injuries. The risk of syncope significantly increases with the concurrent use of a phosphodiesterase-5 (PDE-5) inhibitor.