DRUG CLASSES
Nitrates
Calcium channel blockers
Atherosclerosis is a disease characterized by deposits of fatty plaques on the inner walls of arteries. These deposits result in a narrowing of the lumen (inside diameter) of the artery and a decrease in blood supply to the area served by the artery. Diseases of the arteries can cause serious problems: coronary artery disease, cerebral vascular disease, and peripheral vascular disease. Drug therapy for vascular diseases may include drugs that dilate blood vessels and thereby increase blood supply to an area.
This chapter discusses drugs whose primary purpose is to increase blood supply to an area by dilating blood vessels. Vasodilating drugs relax the smooth muscle layer of arterial blood vessels, which results in vasodilation, an increase in the size of blood vessels, primarily small arteries and arterioles. Because peripheral, cerebral, or coronary artery disease usually results in decreased blood flow to an area, drugs that dilate narrowed arterial vessels permit the vessels to carry more blood, resulting in an increase in blood flow to the affected area. Increasing the blood flow to an area may result in complete or partial relief of symptoms. In some cases, however, drug therapy provides only minimal and temporary relief. Many of the calcium channel blockers and vasodilating drugs are also used to treat hypertension. Their use as antihypertensives is discussed in Chapter 35.
Angina is a disorder characterized by atherosclerotic plaque formation in the coronary arteries, which causes decreased oxygen supply to the heart muscle and results in chest pain or pressure (Fig. 36.1). Any activity that increases the workload of the heart, such as exercise or simply climbing stairs, can precipitate a painful angina attack. Antianginal drugs relieve chest pain or pressure by dilating coronary arteries, increasing the blood supply to the myocardium.
PHARMACOLOGY IN PRACTICE
Mrs. Moore was hospitalized with severe chest pain and a possible myocardial infarction. After tests were completed, her primary health care provider prescribed sublingual nitroglycerin for her angina. Her daughter is calling about severe pain. As you assess the situation you find out it is not her heart but what the daughter calls “severe migraine headaches.” As you read this chapter determine if this pain is related to cardiac function or medications.
The antianginal drugs include the nitrates and the calcium channel blockers. Chapter 25 and its Summary Drug Table: Adrenergic Blocking Drugs discuss the adrenergic blocking drugs that also are used to treat angina and other disorders.
Actions
The nitrates act by relaxing the smooth muscle layer of blood vessels, increasing the lumen of the artery or arteriole, and increasing the amount of blood flowing through the vessels.
Calcium channel blockers have several effects on the heart:
• Slowing the conduction velocity of the cardiac impulse
• Depressing myocardial contractility
• Dilating coronary arteries and arterioles, which in turn deliver more oxygen to cardiac muscle
Dilation of peripheral arteries reduces the workload of the heart. The end effect of these drugs is the same as that of the nitrates. An increased blood flow results in an increase in the oxygen supply to surrounding tissues.
Uses
The antianginal drugs are used in the treatment of cardiac disease to:
• Relieve pain of acute anginal attacks
• Prevent angina attacks (prophylaxis)
• Treat chronic stable angina pectoris
Typically the nitrate group of drugs is used to relieve symptoms when an anginal attack happens, as opposed to the use of the “blocking” drugs to prevent angina from occurring by taking the drug on a regular basis.
Intravenous (IV) nitroglycerin is used to control perioperative hypertension associated with surgical procedures. Calcium channel blocking drugs are also used to treat hypertension (see Chapter 35) and other cardiac conditions. For example, verapamil affects the conduction system of the heart and is used to treat cardiac arrhythmias. See the Summary Drug Table: Antianginal and Vasodilating Drugs for additional uses of the nitrates and calcium channel blockers.
Adverse Reactions
Adverse reactions to the calcium channel blocking drugs usually are not serious and rarely require discontinuation of the drug therapy (see Chapter 35 for specifics). Adverse reactions associated with the nitrates include the following:
• Central nervous system (CNS) reactions, such as headache (may be severe and persistent), dizziness, weakness, and restlessness
• Other body system reactions, such as hypotension, flushing (caused by dilation of small capillaries near the surface of the skin), and rash
The nitrates are available in various forms (e.g., sublingual, translingual spray, transdermal, and parenteral). Some adverse reactions are a result of the method of administration. For example, sublingual nitroglycerin may cause a local burning or tingling in the oral cavity. However, the patient must be aware that an absence of this effect does not indicate a decrease in the drug’s potency. Contact dermatitis may occur from use of the transdermal delivery system.
In many instances, the adverse reactions associated with the nitrates lessen and often disappear with prolonged use of the drug. However, for some patients, these adverse reactions become severe, and the primary health care provider may lower the dose until symptoms subside. The dose may then be slowly increased if the lower dosage does not provide relief from the symptoms of angina. See the Summary Drug Table: Antianginal and Vasodilating Drugs for more information.
Contraindications and Precautions
Nitrates are contraindicated in patients with known hypersensitivity to the drugs, severe anemia, closed-angle glaucoma, postural hypertension, early myocardial infarction (sublingual form), head trauma, cerebral hemorrhage (may increase intracranial hemorrhage), allergy to adhesive (transdermal system), or constrictive pericarditis. Patients taking phosphodiesterase inhibitors (drugs for erectile dysfunction) should not use nitrates.
Nitrates are used cautiously in patients with the following:
• Severe hepatic or renal disease
• Severe head trauma
• Hypothyroidism
These drugs are used cautiously during pregnancy and lactation (pregnancy category C).
Interactions
The following interactions may occur when the nitrates are used with another agent:
NURSING PROCESS
PATIENT RECEIVING AN UPPER RESPIRATORY SYSTEM DRUG
ASSESSMENT
Preadministration Assessment
The person using an antianginal drug for episodic pain is typically an outpatient; therefore, instruction about use is an essential intervention. When you engage in a teaching session, first conduct and document a thorough pain assessment (see Chapter 14) as well as a history of allergy to the nitrates or calcium channel blockers and of other disease processes that would contraindicate administration of the drug. Display 36.1 lists angina-specific example questions. Remember to assess the patient’s health literacy by asking about what he or she may think causes the pain. Also, ask what remedies the patient has used to relieve the pain and whether he or she is able to read and understand directions that you will prepare for the patient.
Be sure to assess the physical appearance of the patient (e.g., skin color, lesions) and auscultate the lungs for adventitious sounds. Tests frequently include a baseline electrocardiogram, stress test, chest x-ray, and laboratory panels. Include weighing the patient when you perform vital signs and note any problem with orthostatic hypotension.
Display 36.1 Angina-Specific Pain Assessment
History
- Describe the pain (e.g., tightness, pressure, sharp, stabbing).
- Location—is it in a specific place or generalized?
- Does the pain spread and where does it spread?
- Does it start suddenly or is it gradual? How long does it last?
- What events tend to cause anginal pain (e.g., exercise, emotion, other triggers)?
- What makes it feel worse (e.g., movement, breathing, activity)?
- What seems to relieve the pain (e.g., resting, position change)?
Ongoing Assessment
As a part of the ongoing assessment, monitor the patient for the frequency and severity of any episodes of anginal pain. This assessment may be conducted by telephone for the patient at home. With treatment, the patient may expect that episodes of angina should be eliminated or decrease in frequency and severity. Instruct the patient to call for emergency assistance if the chest pain does not respond to three doses of nitroglycerin given every 5 minutes for 15 minutes.
Teach the patient or caregiver to monitor vital signs frequently during administration of the antianginals. If the patient’s heart rate falls below 50 bpm or the systolic blood pressure drops below 90 mm Hg, hold the drug and notify the primary health care provider. A dosage adjustment may be necessary. For the patient at home, instruct the patient or the caregiver to also call the primary health care provider and ask if the drug should be given for the next episode of heart-related pain.
Assess patients receiving the calcium channel blockers for signs of heart failure (HF): dyspnea, weight gain, peripheral edema, abnormal lung sounds (crackles/rales), and jugular vein distention. Any symptoms of HF are reported promptly to the primary health care provider. The dosage may be increased more rapidly in hospitalized patients under close supervision. When the drug is being titrated to a therapeutic dose, the patient is typically monitored by telemetry.
NURSING DIAGNOSES
Drug-specific nursing diagnoses include the following:
Risk for Injury related to hypotension, dizziness, lightheadedness
Pain related to narrowing of peripheral arteries, decreased blood supply to the extremities
Nursing diagnoses related to drug administration are discussed in Chapter 4.
PLANNING
The expected outcomes of the patient depend on the specific reason for administering the drug but may include an optimal response to therapy, support of patient needs related to the management of adverse reactions, and confidence in an understanding of the medication regimen.
IMPLEMENTATION
Promoting an Optimal Response to Therapy
NITRATES—STOPPING AN ATTACK. Nitrates may be administered by the sublingual (under the tongue), buccal (between the cheek and gum), oral, IV, or transdermal route. If the buccal form of nitroglycerin has been prescribed, you may want to show the patient how and where to place the tablet in the mouth by using a small sugarless candy. Be sure the patient understands that absorption of sublingual and buccal forms depends on salivary secretion and a dry mouth may decrease the effect.
Nitroglycerin may also be administered by a metered spray canister that is used to stop an acute anginal attack. Be sure the patient understands that the spray is directed from the canister onto or under the tongue. Each dose is metered so that when the canister top is depressed, the same dose is delivered each time. Instruct the patient not to shake the canister or inhale the spray. For some individuals, this is more convenient than placing small tablets under the tongue.
NURSING ALERT
The dose of sublingual nitroglycerin may be repeated every 5 minutes until pain is relieved or until the patient has received three doses in a 15-minute period. One to two sprays of translingual nitroglycerin may be used to relieve angina, but no more than three metered doses are recommended within a 15-minute period.
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