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Nitrates: Nursing Pharmacology

Notes

Notes

NITRATES
DRUG NAME
nitroglycerin (e.g., Nitrolingual, Nitro-Bid, Nitro-Dur, NitroMist); isosorbide dinitrate; isosorbide mononitrate
CLASS
Nitrates
MECHANISM OF ACTION
Relax vascular smooth muscle cells, thereby causing venous and arterial vasodilation; decrease both preload and afterload; relax coronary arteries
INDICATIONS
Angina pectoris, hypertension, heart failure, anal fissure
ROUTE(S) OF ADMINISTRATION
Nitroglycerin
  • S/L
  • PO, PO spray
  • IV
  • Transdermal patch
  • Topical ointment
  • PR

Isosorbide dinitrate, isosorbide mononitrate
  • PO
SIDE EFFECTS
Headache, dizziness, flushing, nausea and vomiting, orthostatic hypotension, reflex tachycardia, tolerance
CONTRAINDICATIONS AND CAUTIONS
  • Hypotension, hypovolemia, severe anemia, cardiomyopathy
  • Use carefully during pregnancy, breastfeeding, children or elderly, increased intracranial pressure, cerebral hemorrhage, renal or hepatic disease, and syncope
  • Drug interactions: other vasodilators (i.e., alcohol or erectile dysfunction medication like sildenafil, tadalafil, or vardenafil)
NURSING CONSIDERATIONS: NITRATES
ASSESSMENT AND MONITORING
Prior to administration
  • Frequency and severity of angina pain
  • Baseline vital signs
  • Health history
  • Laboratory report: CBC, lipid profile renal and hepatic function

Continued monitoring
  • Side effects
  • Worsening symptoms
  • Therapeutic response
CLIENT EDUCATION
Correct self-administration procedures
  • Angina with activity: take prior to precipitating activities or situations
  • Acute angina: call emergency services if pain unresolved within five minutes after first dose; while awaiting emergency care to arrive, may take a second and third dose five minutes apart if needed

Managing side effects
  • Headache: acetaminophen
  • Orthostatic hypotension: make position changes slowly

Proper storage
  • Store in original container at room temperature
  • Protect from light and moisture

Prevention of nitrate tolerance with patches or extended-release forms
  • At least 12 hours of nitrate free time / 24 hours

Avoid substances that cause excessive hypotension
  • E.g., alcohol, erectile dysfunction medications
Transcript

Nitrates are medications that come under the umbrella of a larger group called vasodilators, which dilate the walls of blood vessels. Nitrates are primarily used to treat angina pectoris, which is pain caused by reduced blood flow to the heart muscle; as well as hypertension, and heart failure.

More recently, they’ve also been approved for the topical treatment of anal fissures. The most commonly used nitrates include nitroglycerin, isosorbide dinitrate, and isosorbide mononitrate.

Out of these, nitroglycerin has a rapid and short-lasting action, so it is typically given through rapidly absorbable routes like sublingual, oral spray, or intravenously, to treat acute anginal pain or hypertension; or as transdermal patches or topical ointments for long-term prevention. Nitroglycerin can also be administered rectally for the treatment of anal fissures.

On the other hand, isosorbide dinitrate and isosorbide mononitrate have a longer duration of action and are typically administered orally as tablets or sustained-release capsules, which makes them useful for the long-term prevention of angina pectoris, or to treat clients with heart failure.

Once absorbed into the blood, nitrates quickly get converted into their active form, called nitric oxide. Nitric oxide diffuses to the smooth muscle cells of both veins and arteries, causing wall relaxation and vasodilation.

The result of venous vasodilation is peripheral blood pooling, which in turn decreases the return of venous blood to the heart.

This way, nitrates predominantly reduce preload, which is the pressure that stretches the heart as it fills with blood from venous return.

At the same time, arterial vasodilation lowers the systemic vascular resistance, which will also reduce the afterload, or the pressure that the heart must work against to eject the blood.

Ultimately, by reducing preload and afterload, nitrates reduce the amount of work the heart has to do, eventually decreasing the heart’s oxygen consumption.

Nitrates also have a minor effect on the dilation of the coronary arteries, which helps increase oxygen delivery to heart tissue.

Common side effects of nitrates include headache, dizziness, flushing, nausea and vomiting. Another important side effect of nitrates is orthostatic hypotension, where the blood pressure falls significantly when the client stands up too quickly.

As a result, these clients could experience lightheadedness or syncope due to decreased blood flow to the brain.

In addition, clients may experience reflex tachycardia, which is caused by the sympathetic system triggering an increase in heart rate in response to the hypotension caused by nitrates, in order to maintain tissue perfusion.

Now, clients who continuously use nitrates soon develop tolerance to these side effects. Unfortunately, clients may also develop tolerance to the therapeutic effects of nitrates, especially with uninterrupted use; clients can prevent this by avoiding using nitrates for several hours each day.

Finally, nitrates are contraindicated in individuals with hypotension, hypovolemia, severe anemia, and cardiomyopathy.

Nitrates should be used carefully during pregnancy or breastfeeding, as well as in clients with increased intracranial pressure or cerebral hemorrhage, renal or hepatic disease, and syncope.

As far as drug interactions go, nitrates should never be combined with other substances that cause vasodilation, such as drinking alcohol, as well as medications used to treat erectile dysfunction, including sildenafil, tadalafil, or vardenafil.

If taken together, their effects add up and may lead to a steep fall in blood pressure, cardiovascular collapse, and even death.

Now, before administering a nitrate, complete a baseline assessment, including frequency and severity of angina pain and vital signs, especially blood pressure.

Review their health history for angina risk factors, such as hypertension. Next, check your client’s latest laboratory report, including CBC, hepatic and renal function, as well as their lipid profile.

Sources
  1. "Focus on Nursing Pharmacology" LWW (2019)
  2. "Pharmacology" Elsevier Health Sciences (2014)
  3. "Mosby's 2021 Nursing Drug Reference" Mosby (2020)
  4. "Saunders Comprehensive Review for the NCLEX-RN Examination" Saunders (2016)
  5. "Goodman and Gilman's The Pharmacological Basis of Therapeutics, 13th Edition" McGraw-Hill Education / Medical (2017)