6.10 Antihypertensives

Many different medication classifications are used to treat hypertension. Nurses must understand the different mechanisms of action for different classes of antihypertensives because clients are often on a combination of medications that work synergistically to manage blood pressure. These medications are also discussed in the “Autonomic Nervous System” chapter, with more information provided regarding the specific receptors they affect.

Alpha-2 Agonist

Clonidine is an Alpha-2 agonist. You can read more information about Alpha-2 agonists in the “Autonomic Nervous System” chapter.

Mechanism of Action: Clonidine stimulates the alpha-adrenergic receptors, resulting in vasodilation and decreased blood pressure, thus decreasing peripheral resistance, increased blood flow to the kidneys, and decreased afterload.

Indications: Clonidine is used to treat hypertension and ADHD.

Nursing Considerations: Monitor BP and pulse rate. Dosage is usually adjusted to client’s blood pressure because it can cause hypotension, bradycardia, and sedation. Rebound hypertension may occur if stopped abruptly.^[1]

Side Effects/Adverse Effects: Clients should be monitored for side effects including hypotension, bradycardia, and sedation. If individuals cease taking the medication too suddenly, they may experience rebound hypertension.

Health Teaching & Health Promotion: Clients should be compliant with medication therapy and take the medication at the same time each day. They should be careful not to take more than the prescribed dose within a 24-hour period. Do not abruptly cease medication as rebound hypertension might occur. Medications may cause orthostatic changes so individuals should change positions slowly. Additionally, medications may cause dry mouth and dry eyes. Individuals should also avoid the use of alcohol and other CNS depressants while taking these medications.^[2]

Now let’s take a closer look at the medication grid for clonidine in Table 6.10a.^[3]

Table 6.10a Clonidine Medication Grid

Beta-1 Antagonist

Metoprolol is a selective Beta-1 blocker. You can read more information about Beta-1 antagonists in the “Autonomic Nervous System” chapter.

Mechanism of Action: Metoprolol primarily blocks Beta-1 receptors in the heart, causing decreased heart rate and decreased blood pressure. However, higher doses can also block Beta-2 receptors in the lungs, causing bronchoconstriction.

Indications: Metoprolol is commonly used to treat high blood pressure, chest pain due to poor blood flow to the heart, and several heart conditions involving an abnormally fast heart rate. It is used as an early intervention during myocardial infarction (MI) to reduce workload of the heart.

Nursing Considerations: Extended-release (ER) formulations should not be crushed. Assess client’s apical pulse rate before administering; if it is less than 60 beats/minute, withhold the drug and call the provider immediately, unless other parameters are provided. In diabetic clients, monitor glucose level closely because the drug masks common signs and symptoms of hypoglycemia.

Side Effects/Adverse Effects: Other adverse effects include fatigue, dizziness, depression, insomnia, nightmares, GI upset, erectile dysfunction, dyspnea, and wheezing.

Boxed Warning: The most serious potential adverse effects are shortness of breath, bradycardia, and worsening heart failure. When stopping therapy, taper dosage over 1 to 2 weeks because abrupt discontinuation may cause chest pain or MI.^[4]

Health Teaching & Health Promotion: Clients should be compliant with medication therapy and take the medication at the same time each day. Do not abruptly cease medication as arrhythmias, hypertension, or ischemia may develop. Clients and families should be instructed to check pulse and blood pressure and report abnormalities to the health care provider. Additionally, these medications may cause side effects of dizziness and cold sensitivity.^[5]

Now let’s take a closer look at the medication grid for metoprolol in Table 6.10b.^[6]

Table 6.10b Metoprolol Medication Grid

ACE Inhibitor (Angiotensin Converting Enzyme)

Captopril is an example of an ACE (angiotensin converting enzyme) inhibitor.

Mechanism of Action: This medication blocks the conversion of Angiotensin I to Angiotensin II in the renin-angiotensin-aldosterone system. This will lead to vasodilation and sodium and water excretion by blocking aldosterone. See more information about the renin-angiotensin-aldosterone system in the “Basic Concepts of the Cardiovascular and Renal Systems” section of this chapter.

Indications: Captopril is used to treat hypertension and heart failure. This medication also helps reduce diabetic nephropathy.

Nursing Considerations: Do not administer to clients who are pregnant. Use with caution with clients who have diabetes.

Avoid use with other medications that increase potassium. This medication may increase risk for lithium toxicity.

Side Effects/Adverse Effects: Clients taking this medication may experience hypotension, cough, hyperkalemia, increased risk for infection, angioedema, anaphylactoid reactions, or proteinuria. Clients who experience increased facial swelling or difficulty swallowing or breathing should seek emergency medical attention. Report a persistent cough or angioedema to the health care provider.^[7]

Boxed Warning: Clients who become pregnant should discontinue this medication due to the risk of fetal harm or fetal death.

Health Teaching & Health Promotion: Medications should be taken as directed. Clients taking ACE inhibitors should be cautioned to avoid salt substitutes or other foods high in potassium because this medication increases the risk for hyperkalemia. Additionally, the medication may alter the sense of taste, but this generally resolves within 2-3 months of medication therapy.

Clients taking ACE inhibitors may also experience a persistent cough throughout the duration of medication therapy.^[8]

Now let’s take a closer look at the medication grid for captopril in Table 6.10c.^[9] 

Table 6.10c Captopril Medication Grid

Angiotensin II Receptor Blocker (ARB)

Losartan is an example of an Angiotensin II receptor blocker, also referred to as an ARB. ARBs are similar to ACE inhibitors in that they act on the renin-angiotensin-aldosterone system (RAAS). However, the difference is that they block Angiotensin II and cause vasodilation and decreased peripheral resistance but are not likely to cause the cough that ACE inhibitors can.

Mechanism of Action: Losartan blocks Angiotensin II in the renin-angiotensin-aldosterone system to produce vasodilation.

Indications: ARB is used for treatment of hypertension and to prevent nephropathy in diabetic clients.

Nursing Considerations: Do not administer to clients who are pregnant. It is not recommended for children under 6. Anticipate dosage adjustment with hepatic impairment. This drug can cause renal impairment and hyperkalemia.

Side Effects/Adverse Effects: Clients taking this medication may experience hypotension, dizziness, increased risk for infection, angioedema, or proteinuria. Clients who experience increased facial swelling or difficulty swallowing or breathing should seek emergency medical attention.

Boxed Warning: Clients who become pregnant should discontinue this medication due to the risk of fetal harm or fetal death.

Health Teaching & Health Promotion: Medications should be taken as directed at the same time each day. Clients should not discontinue therapy unless directed to by their health care provider. Clients should be careful to avoid salt substitutes and foods with high levels of potassium. ARBs may cause orthostatic changes, and clients should be cautioned to change positions slowly.^[10]

Now let’s take a closer look at the medication grid for losartan in Table 6.10d.^[11]

Table 6.10d Losartan Medication Grid

Vasodilator

Hydralazine is an example of a direct vasodilator.

Mechanism of Action: Hydralazine’s direct mechanism of action is unknown, but it causes vasodilation via direct relaxation of vascular smooth muscle. Peripheral vasodilation results in a reduction of blood pressure and decreased vascular resistance, resulting in increased cardiac output.

Indications: Vasodilators are used to treat hypertension.

Nursing Considerations: Use with caution in clients with coronary artery disease, mitral valve rheumatic heart disease, and cerebral vascular accidents.

This medication should only be used in pregnancy if the benefits outweigh the risks due to lack of safety studies.

Side Effects/Adverse Effects: Clients should be monitored for infection and are at risk of developing systemic lupus erythematosus (SLE). SLE is a chronic disease that causes inflammation in connective tissues. The signs and symptoms of SLE vary among affected individuals and can involve many organs and systems, including the skin, joints, kidneys, lungs, central nervous system, and blood-forming (hematopoietic) system. A characteristic sign of SLE is a flat, red rash across the cheeks and bridge of the nose. This rash is called a “butterfly rash” because of its shape.

Hypotension, palpitations, angina, tremors, numbness, tingling, disorientation, nasal congestion, headache, nausea, vomiting, and diarrhea are effects associated with hydralazine.^[12]

Health Teaching & Health Promotion: Clients should remain compliant with the therapeutic dosing regimen, even if symptoms resolve. The client should be cautious not to double up on medication doses. Additionally, the client should consult the health care provider if two or more doses of medication are missed for follow-up instruction. Clients should be instructed to monitor their weight and assess for fluid retention in the feet and ankles. Additionally, the medication can cause side effects of orthostatic hypotension and drowsiness.^[13]

Now let’s take a closer look at the medication grid on hydralazine in Table 6.10e.^[14]

Table 6.10e Hydralazine Medication Grid