Antihypertensive Medications Overview

Antihypertensive Medications

• Antihypertensive medications reduce blood pressure and workload on the heart.
• Digoxin is an exception; it doesn’t affect blood pressure but slows heart rate and improves cardiac contractility.
• Slow position changes are essential when giving antihypertensives to prevent orthostatic hypotension, which is a drop in blood pressure upon standing.

ACE Inhibitors

• ACE inhibitors (ending in “-pril”) are the first choice for blood pressure reduction.
• They lower blood pressure but not heart rate.

Angiotensin Receptor Blockers (ARBs)

• ARBs (ending in “-sartan”) are the second choice for blood pressure reduction.
• They also lower blood pressure without affecting heart rate.
• ACE inhibitors and ARBs can be given even if the heart rate is bradycardic (below 60 bpm).

Renin-Angiotensin-Aldosterone System (RAAS)

• The RAAS maintains fluid and salt balance, impacting blood pressure.
• Renin is released in response to low blood pressure, converting angiotensinogen to angiotensin I.
• ACE converts angiotensin I to angiotensin II, which increases blood pressure by promoting sodium & water reabsorption and vasoconstriction.

ACE Inhibitors and ARBs Mechanisms of Action

• ACE inhibitors block ACE, preventing the conversion of angiotensin I to angiotensin II, thus reducing fluid retention and vasoconstriction.
• ARBs prevent angiotensin II from binding to receptors in the kidneys and arteries, resulting in vasodilation and preventing sodium reabsorption.
• Both ACE inhibitors and ARBs inhibit or block the RAAS, lowering blood pressure.

Aldosterone

• Aldosterone is blocked from adding sodium and water and letting potassium out.

Digoxin

• Digoxin increases the force of cardiac contractions (positive inotropic effect) and is used for systolic heart failure.
• It is a negative chronotropic agent, meaning it decreases heart rate.
• It has a narrow therapeutic index, making it toxic at high doses.

Digoxin Nursing Considerations

• Always check the apical pulse for a full 60 seconds before administering Digoxin.
• Do not give the drug if the heart rate is below 60 bpm.
• Digoxin toxicity may occur at levels above 2.0 ng/mL; the normal level is 0.8-2.0 ng/mL.
• Early signs of toxicity include vision changes, nausea/vomiting, anorexia, dizziness, lightheadedness.
• Older patients with decreased kidney function are at high risk for toxicity.
• Monitor BUN and creatinine levels (creatinine is the primary indicator of kidney function).
• A creatinine level over 1.3 mg/dL indicates kidney injury.
• A low potassium level (below 3.5 mEq/L) increases the risk of Digoxin toxicity.

Nitrates

• Nitrates (e.g. nitroglycerin) convert to nitric oxide, a vasodilator, causing significant dizziness.
• Nitroglycerin lowers blood pressure quickly.

Nitroglycerin Nursing Considerations

• Contraindications include use with PDE-5 inhibitors (e.g., sildenafil) as it can cause dangerously low blood pressure.
• Adverse effects include severe hypotension.
• Patient should carry nitroglycerin at all times with a current bottle for frequent expiration date checks.
• Stop nitroglycerin if systolic BP is <90 or 100 mmHg or drops >30 points. Watch for signs of hypotension — confusion, agitation, pale/cold/clammy skin, diaphoresis.

Nitroglycerin Side Effects

• Common side effects include headache, dizziness, and flushing (3 Hs).
• Teach patients about slow position changes and to check blood pressure before taking nitroglycerin.

Nitroglycerin Forms

• Nitroglycerin pills are for stable angina, which is stress-induced and ceases at rest.
• Nitroglycerin patches are for unpredictable angina that can occur anytime.

Nitroglycerin Pill Administration

• If chest pain persists 5 minutes after the first dose, call emergency services.
• Give up to three doses 5 minutes apart.
• Place under the tongue (sublingual); do not swallow.
• Store in a cool, dark place and replace every 6 months.

Diuretics

• Diuretics are used to increase urine output, reducing fluid volume and blood pressure.

Diuretic Classification and Order of Diuresis

• Osmotic diuretics (e.g. Mannitol) work in the proximal convoluted tubule (PCT) and increase osmotic pressure.

• Loop diuretics (e.g. Furosemide) act on the loop of Henle, inhibiting sodium and chloride reabsorption.

• Thiazide diuretics (e.g. Hydrochlorothiazide) inhibit sodium and chloride reabsorption in the distal convoluted tubule (DCT).

• Potassium-sparing diuretics (e.g. Triamterene, Spironolactone) work in the collecting duct, exchanging sodium for potassium and preventing potassium excretion.

• The order of diuretic effectiveness from greatest to least diuresis is:

  • Osmotic
  • Loop
  • Thiazide
  • Potassium-sparing

Mannitol (Osmitrol)

• Mannitol is an osmotic diuretic used to reduce intracranial and intraocular pressure.
• It works in the PCT, preventing sodium and water reabsorption.
• It can cause dehydration and electrolyte imbalances.

Furosemide (Lasix)

• Furosemide is a loop diuretic that prevents sodium reabsorption in the loop of Henle.
• It is commonly used for edema and hypertension.
• Side effects include hypokalemia and ototoxicity.

Hydrochlorothiazide (Microzide)

• Hydrochlorothiazide is a thiazide diuretic that prevents sodium reabsorption in the DCT.
• It is used for hypertension and edema.
• Side effects include hypokalemia.

Loop Diuretics Nursing Considerations

• Loop diuretics (e.g., furosemide) are first-line drugs for acute heart failure or worsening heart failure.

Diuretic Nursing Considerations

• Monitor weight daily for fluid retention (report a gain of 2-3 lbs in a single day).
• Encourage high-potassium foods (e.g., melons, bananas, leafy greens, liver) unless the patient has a pre-existing potassium imbalance. Avoid licorice root, which lowers potassium.
• Monitor BUN and creatinine for possible renal damage.
• Teach patients to wear sunblock due to increased sun sensitivity.
• Limit sodium intake: follow a low-sodium diet.
• Avoid medications containing high sodium (e.g., canned soups, processed foods, packaged foods).
• Do not give potassium via IV push (risk of instant death).
• Slow position changes to prevent postural hypotension.

Furosemide (Lasix) Nursing Considerations

• Administer Furosemide slowly; rapid administration can cause hypokalemia.
• Long-term use can cause renal damage and hypokalemia.

Clonidine

• Clonidine is an alpha-2 adrenergic agonist that reduces sympathetic outflow from the brainstem, decreasing the heart rate and blood pressure.
• It is used as a last resort for persistent high blood pressure that doesn't respond to other medications.

Clonidine Mechanism of Action

• Decreases heart rate.
• Decreases cardiac output.
• Decreases blood pressure.

Clonidine Administration

• Clonidine patch should be changed every 7 days.
• Apply the patch to a hairless, intact skin area, preferably on the upper arm.

Clonidine Nursing Considerations

• Do not stop taking Clonidine abruptly, as it can cause severe rebound hypertension (systolic BP > 180 mmHg) leading to heart attack or stroke.
• Taper Clonidine slowly when discontinuing.
• Teach patients about slow position changes to prevent postural hypotension.
• Avoid CNS depressants (e.g., alcohol, sedatives) while taking Clonidine, as they can further lower blood pressure.

This quiz covers key concepts related to antihypertensive medications, including ACE inhibitors and ARBs. Understand their mechanisms, effects on blood pressure, and considerations for use. Dive deep into the Renin-Angiotensin-Aldosterone System and its role in blood pressure management.