Safe Usage of Nitrates for Angina

• It is important to understand the commonly prescribed nitrates that are used for angina and the actions/uses of these medications.
• The drug interactions and adverse effects must by understood in an effort for uneventful occurrences to be noted.
• The nurse has an important role to play in assessment and patient education regarding the use of nitrates for angina.  

Commonly Prescribed Nitrates

Nitrates are the most commonly used agents to treat acute angina.  The cardinal symptom of angina is chest pain.  In order to relieve chest pain, antianginal drugs are the essential agents that reduce the myocardial oxygen demands. 

The commonly prescribed nitrates for angina are: 

• Amyl nitrate  
• Isosorbide dinitrate  
• Isosorbide mononitrate 
• Nitroglycerin 
  

Nitrates can be administered through various routes and can be given accordingly:

• Sublingual – under the tongue  
• Buccal – placed in the pocket of the cheek  
• Lingual aerosols – sprayed onto or under the tongue  
• Chewable tablets 

Drugs through all these routes are quickly and well absorbed due to the rich blood supply of the mucous membranes of the mouth.  

Amyl nitrate can also be given through the inhalation route because it is volatile and a potent vasodilator.  

Swallowed nitrate capsules are absorbed through the mucosa of the digestive tract and only about half of it enters the blood circulation.  

IV nitroglycerin enters the bloodstream directly.  

When applied via transdermal patch or an ointment, the drug absorption is variable, depending on the following factors: 

• Amount of drug applied 
• The location where the patch or the ointment is applied  
• The blood circulation of the skin  
• The surface area of the skin used
  

Actions and Uses of Nitrates

Actions of Nitrates

Nitrates are potent vasodilators. They relax the smooth muscles of the veins and the arteries, hence resulting in dilation. 

When the veins dilate, the less deoxygenated blood reaches the heart, which in turn reduces the amount of blood in the ventricles at the end of diastole, when the ventricles are full.  When this occurs, this volume is known as preload.  

When preload reduces, ventricular size and ventricular wall tension are also reduced.  At this point, the left ventricle does not have to stretch as much to pump blood, which in turn reduces the oxygen demands of the heart.   

The arteries resist the blood pumped by the left ventricle which is also known as peripheral vascular resistance.  Nitrates dilate arterioles, reducing afterload and resistance, which in turn eases the heart’s workload and makes it easier to meet oxygen demands.  

Uses of Nitrates

Nitroglycerin is used to relieve and prevent angina.  

Rapidly absorbed nitrate such as nitroglycerin is a drug of choice to relieve angina because it has a rapid onset of action, is inexpensive, and is easy to take.  

Long-acting nitrates, such as transdermal patches are used to prevent chronic angina.  They are convenient to use.  Oral nitrates are also used in the long term to prevent angina because they seldom produce adverse reactions. 

Drugs Interactions and Adverse Effects of Nitrates

The drug interactions that can occur with nitrates are as follows: 

• When taken with alcohol, nitrates can result in severe hypotension.  Be certain to inform the patient to abstain from alcohol intake with nitrate therapy.  
• Do not give Sildenafil within 24 hours of nitrate therapy because of its enhanced hypotensive effects.  
• Oral nitrates, when given with an anticholinergic drug an result in delayed absorption of the nitrates.  Do not administer together.  
• When calcium channel blockers are given with nitrates, it can cause marked orthostatic hypotension, dizziness, and fainting.  If both need to be administered, the dosage may need to be adjusted.   
  

The common adverse effects of nitrates are as follows:

• Flushing  
• Nausea 
• Hypotension  
• Dizziness or lightheadedness 
• Orthostatic hypotension  
• Headache  
• Increased heart rate
  

The adverse effects of nitrates are often related to changes in the cardiovascular system and are dose-dependent. When you reduce the dose, the adverse reactions often disappear.

Nursing Role in Nitrate Administration and Patient Education

It is important for nurses to understand the vital role they play in the administration and management of nitrates and important nursing areas that must be considered.   

The following nursing processes are appropriate for a patient undergoing nitrate therapy: 

Assessment

• Monitor the vital signs of the patient. 
• With IV nitroglycerin therapy, monitor the pulse and blood pressure every 5 to 15 minutes.  Make the necessary dosage adjustments accordingly.  
• Observe for adverse drug reactions.
• Monitor the effectiveness of the drug. 

Key Nursing Diagnoses

• Risk for injury because of adverse effects such as dizziness and fainting
• Excess fluid volume because of adverse cardiovascular effects
• Deficient knowledge of drug therapy and its administration 

Implementation

• Give the nitrate tablets on an empty stomach, either 30 minutes or 1 to 2 hours before a meal.  
• Tell the patient to swallow the oral tablets and to not chew them.  
• When administering the first nitrate dose, keep the patient sitting or lying down.  
• Before starting the therapy and after the drug shows its effects, monitor the patient’s blood pressure and pulse rate.  
• Do not give a concomitant beta blocker or calcium channel blocker with nitrate therapy to relieve angina.  
• If the patient’s heart rate is less than 60 bpm and systolic blood pressure drops below 90 mm of Hg, withhold the nitrate therapy or follow the physician’s order.  
• Dilute IV nitroglycerin with D5W or normal saline solution for injection, using a glass bottle.  Avoid using IV filters because they can bind to the plastic.  A special nonabsorbent polyvinyl chloride tubing is available to be used.  Titrate the drug and administer it with an infusion-controlled device and make certain the concentration does not exceed 400 mcg/ml.   
• Administer sublingual nitroglycerin at the first sign of the attack.  Place the medication under the tongue until it dissolves completely.  It can be repeated every 5 minutes for up to three doses.  
• Place the prescribed nitrate ointment on a piece of paper and place it on a non-hairy area of the body and cover it with plastic.  While applying the next dose, remove the previously applied one and be careful to not get ointment on your fingers while applying it to the patient (as this can cause a headache).   
• Before defibrillation, remove the transdermal patch since its aluminum backing can explode with the electric current.  
• Be aware that initially, the patient may have a headache that subsidizes when tolerance develops, or the dose is reduced.  

Patient Teaching

With nitrate therapy, it is essential to teach the following points to the patient and caregiver(s): 

• Understand the form of drug prescribed and the route of administration.  Make certain it is taken through the appropriate route.  
• Take the drug regularly and be certain to have it accessible at all times.  
• Without the prescriber’s approval, do not discontinue the drug abruptly, as it can lead to coronary vasospasm.  If any adverse effects occur from the drug therapy, consult with a healthcare provider.  
• With nitrate therapy, an additional dose may be needed before anticipated stress or at bedtime if one has a complaint of nocturnal angina.  
• Be cautious while using the microwave oven when wearing a transdermal patch, as the leaking radiations may heat the aluminum backing of the patch and lead to burns.  
• Avoid consuming alcohol with nitrate therapy because it can lead to severe hypotension.  
• Before applying the new transdermal patch, remove the old one. 
• Change positions slowly, especially when changing into an upright position.  Go up and down the stairs slowly.  Lie down at any first signs of dizziness.  
• Store sublingual tablets in a separate air-tight container, not in a pocket close to one’s body or purse.  
• Before taking the medication, check one’s pulse.  Consult the doctor if pulse is below 60 beats per minute.  
• If three sublingual nitroglycerin tablets are taken 5 minutes apart and do not relieve chest pain, visit the emergency department as soon as possible.  
• For severe or persistent adverse drug reactions, consult the prescriber.  
• To consume buccal tablets, place them between your lip and gum above the incisors or between your cheek and gum.  Do not swallow or chew the tablet. 

The Bottom Line

Nitrates remain essential agents in relieving the symptoms of angina.  They are potent vasodilators and the patient’s blood pressure and heart rate must be monitored throughout therapy.  

They are useful in those dealing with angina and assist many people with increased comfort levels due to decreasing the intensity of chest pain.  It is important to ensure that patients are aware of the uses, adverse effects, and education that pertains to nitrates in order to experience the best possible outcomes.   

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