Cardiovascular medications nursing reference: antihypertensives, antiarrhythmics, and digoxin

Cardiovascular pharmacology is among the highest-yield NCLEX content areas — and the most commonly tested in clinical settings. Nurses administer antihypertensives, antiarrhythmics, and cardiac glycosides daily across med-surg, telemetry, cardiac step-down, ICU, and outpatient cardiology. The consequences of administering these drugs incorrectly, or failing to recognize toxicity, are immediately life-threatening.

This reference covers three major domains: antihypertensives (ACE inhibitors, ARBs, beta-blockers, calcium channel blockers, diuretics), antiarrhythmics (Vaughan-Williams classification, amiodarone, adenosine), and digoxin. For each drug class, you’ll find mechanism, key side effects, hold parameters, and the specific NCLEX facts examiners test. Use it alongside the heart failure nursing guide, the hypertension nursing reference, and the atrial fibrillation nursing guide for integrated clinical coverage.

Fast-scan: cardiovascular drug class overview

Antihypertensives

Hypertension affects roughly half of US adults and is a primary driver of cardiovascular morbidity and mortality. The JNC 8 guidelines established a tiered approach to pharmacological management — with thiazide diuretics, ACE inhibitors, ARBs, and calcium channel blockers as first-line options. Beta-blockers remain essential for specific co-indications. Nurses must understand not only the drug but the patient context that determines drug selection.

ACE inhibitors

Mechanism: ACE inhibitors (angiotensin-converting enzyme inhibitors) block the conversion of angiotensin I to angiotensin II, a potent vasoconstrictor. Without angiotensin II, aldosterone secretion drops, blood pressure falls, and the kidneys retain less sodium and water. The result is reduced afterload, reduced preload, and protection against maladaptive cardiac remodeling — which is why these drugs are first-line in both hypertension and heart failure with reduced ejection fraction.

Drug names — suffix pattern: All ACE inhibitors end in “-pril”: lisinopril, enalapril, ramipril, captopril, fosinopril. The suffix alone is an NCLEX signal to apply ACE-I nursing considerations.

Key side effects and nursing considerations:

Dry cough — The most common reason patients stop ACE inhibitors. Bradykinin accumulates when ACE is inhibited (bradykinin is normally broken down by ACE), and bradykinin accumulation in the airways triggers a persistent, non-productive cough. This is a pharmacological effect, not an allergy. The clinical response: switch to an ARB, which doesn’t affect bradykinin. On NCLEX, “patient taking lisinopril reports a dry cough” → discontinue the ACE-I, switch to an ARB.

Hyperkalemia — ACE inhibitors reduce aldosterone, which means potassium excretion decreases. Monitor potassium levels, especially in patients with CKD or those taking potassium supplements, potassium-sparing diuretics (spironolactone), or NSAIDs. Dangerous hyperkalemia combinations: ACE-I + potassium-sparing diuretic — see the drug interaction table below.

Angioedema — A rare but potentially life-threatening reaction. Swelling of the lips, tongue, larynx, or pharynx can cause airway obstruction. Angioedema occurs more commonly in Black patients and may appear months to years after starting the drug — it is not always an early reaction. Nursing action: Stop the ACE inhibitor immediately, call the provider, assess airway, prepare for potential epinephrine administration. This is a hard hold — the drug is permanently discontinued, not held temporarily. ARBs may also cause angioedema in susceptible individuals, though the risk is lower.

First-dose hypotension — Especially pronounced in patients who are volume-depleted or on concurrent diuretics. Have the patient sit or lie down after the first dose; advise rising slowly.

Teratogenicity — ACE inhibitors are category D/X in pregnancy. They cause fetal renal agenesis, oligohydramnios, and neonatal renal failure. Never administer to pregnant patients.

ARBs (angiotensin receptor blockers)

Mechanism: ARBs block the angiotensin II receptor (AT1 receptor) directly, preventing angiotensin II from binding and exerting its vasoconstricting, aldosterone-stimulating effects. The outcome is nearly identical to ACE inhibition — reduced blood pressure, reduced aldosterone, kidney protection — with one important difference: ARBs do not affect bradykinin levels, so they do not cause the dry cough that frequently ends ACE-I therapy.

Drug names — suffix pattern: All ARBs end in “-sartan”: losartan, valsartan, irbesartan, olmesartan, candesartan.

Key considerations:

• Same indication as ACE inhibitors: hypertension, heart failure, diabetic nephropathy, post-MI
• Hyperkalemia risk is similar to ACE-I — monitor potassium, avoid K+-sparing diuretics without close monitoring
• Angioedema risk exists but is lower than with ACE inhibitors; however, patients with prior ACE-I angioedema should be closely monitored if switched to an ARB
• Never combine an ARB with an ACE inhibitor — dual RAAS blockade significantly increases the risk of hyperkalemia, hypotension, and renal failure without meaningful clinical benefit
• Teratogenic — same category as ACE inhibitors, contraindicated in pregnancy

For nursing students managing patients on blood pressure medications, the hypertension nursing reference covers patient education and lifestyle modification in detail.

Beta-blockers

Mechanism: Beta-blockers competitively antagonize catecholamines (epinephrine, norepinephrine) at beta-adrenergic receptors. Beta-1 blockade in the heart reduces heart rate (negative chronotropy) and contractility (negative inotropy), lowering cardiac output and blood pressure. Beta-2 blockade causes bronchospasm — clinically relevant in patients with asthma or COPD.

Drug names — suffix pattern: Most beta-blockers end in “-olol”: metoprolol, atenolol, propranolol, carvedilol (exception — but widely used). Carvedilol is also an alpha-1 blocker, causing additional vasodilation.

Key side effects and nursing considerations:

Hold for heart rate <60 bpm — Standard nursing practice. Before administering any beta-blocker, assess the apical heart rate for one full minute. If HR is below 60 (or per the provider’s specific parameters), hold the dose and notify the provider. Document this assessment. This is one of the most frequently tested NCLEX nursing actions for cardiac medications.

Never abruptly discontinue — Stopping a beta-blocker suddenly leads to rebound adrenergic stimulation — upregulation of beta-receptors has occurred during chronic blockade. Abrupt withdrawal causes rebound hypertension, tachycardia, angina, and potentially MI. Taper doses over 1–2 weeks under provider supervision. NCLEX priority: if a patient says they’ve been stopping and starting their metoprolol based on how they feel, this is a safety concern requiring immediate patient education and provider notification.

Contraindicated in decompensated heart failure — Beta-blockers are evidence-based for stable, compensated heart failure (carvedilol, metoprolol succinate, and bisoprolol are the three with mortality benefit). But in acutely decompensated HF, adding negative inotropy worsens the situation. The heart failure nursing guide covers this distinction in clinical context.

Contraindicated in reactive airway disease — Beta-2 blockade causes bronchoconstriction. Avoid non-selective beta-blockers (propranolol) in asthma or COPD. Selective beta-1 agents (metoprolol, atenolol) are relatively safer but should still be used cautiously.

Masks hypoglycemia signs — Epinephrine-driven hypoglycemia symptoms — tachycardia, tremor, palpitations — are blunted by beta-blockade. Diabetic patients on insulin or sulfonylureas may have severe hypoglycemia with no warning signs other than diaphoresis (which is cholinergic, not adrenergic, so it’s preserved). Teach patients to monitor blood glucose closely and not to rely on symptoms to detect lows.

Other nursing points: Monitor for fatigue, sexual dysfunction (under-reported and a common reason for non-adherence), cold extremities, and depression.

Calcium channel blockers

Mechanism: CCBs block voltage-gated L-type calcium channels in cardiac and vascular smooth muscle, preventing calcium entry that drives muscle contraction. The specific clinical effect depends on which calcium channels predominate — cardiac versus vascular.

The dihydropyridine vs non-dihydropyridine distinction — high yield for NCLEX:

Dihydropyridines (DHPs) — act preferentially on peripheral vascular smooth muscle. Examples: amlodipine, nifedipine, felodipine. These drugs produce potent vasodilation with minimal direct cardiac effects. They lower blood pressure effectively but cause reflex tachycardia and are more likely to cause peripheral edema (lower extremity swelling from increased capillary hydrostatic pressure — not fluid overload). Amlodipine is the most commonly prescribed CCB and one of the most commonly prescribed antihypertensives overall.

Non-dihydropyridines (non-DHPs) — act on both cardiac and vascular tissue. Examples: diltiazem, verapamil. These drugs slow conduction through the AV node, decrease heart rate, and reduce contractility in addition to causing vasodilation. They are used for rate control in atrial fibrillation and SVT, as well as for hypertension and angina. Their cardiac effects are clinically important: combining a non-DHP CCB with a beta-blocker can cause profound bradycardia or AV block.

Key nursing considerations:

Grapefruit interaction — Grapefruit and grapefruit juice inhibit CYP3A4, the enzyme responsible for metabolizing most CCBs. Inhibiting this enzyme increases plasma drug levels, potentially causing hypotension, reflex tachycardia, or edema. Instruct patients to avoid grapefruit while on calcium channel blockers — this interaction applies to all CCBs and is a classic NCLEX pharmacology question.

Peripheral edema — Common with dihydropyridines, especially amlodipine. Teach patients this is a vasodilatory effect, not fluid overload. Elevating legs helps; dose adjustment or switching agents may be needed if severe.

AV node effects with non-DHPs — Monitor heart rate and rhythm. Do not combine verapamil or diltiazem with beta-blockers without close cardiac monitoring — the combination can cause AV block, severe bradycardia, or asystole.

Constipation — A class effect, more prominent with verapamil; counsel patients accordingly.

Thiazide and loop diuretics

Mechanism:

Thiazide diuretics (hydrochlorothiazide, HCTZ; chlorthalidone) inhibit sodium-chloride cotransporters in the distal convoluted tubule, promoting sodium and water excretion. They are mild diuretics — effective enough for hypertension management, not potent enough for acute fluid overload.

Loop diuretics (furosemide, bumetanide, torsemide) inhibit the Na-K-2Cl cotransporter in the thick ascending limb of the loop of Henle — the most sodium-absorbing segment of the nephron. This makes loop diuretics the most potent diuretics available, capable of producing rapid, large-volume diuresis. Furosemide (Lasix) is the most commonly used.

Key nursing considerations — diuretics:

Hypokalemia — Both thiazide and loop diuretics cause potassium loss. Hypokalemia is dangerous in cardiac patients because it increases cardiac excitability and potentiates digoxin toxicity (covered in depth below). Monitor electrolytes, encourage dietary potassium (bananas, oranges, potatoes, leafy greens), and follow protocols for replacement. Review electrolyte imbalances in nursing for a complete hypokalemia management reference.

Furosemide ototoxicity — High-dose IV furosemide can cause temporary or permanent hearing loss and tinnitus. Risk is highest with rapid IV infusion, high doses, and concurrent use of other ototoxic drugs (aminoglycosides, vancomycin). Administer IV furosemide at a rate no faster than 4 mg/minute. Monitor for tinnitus, dizziness, or hearing changes.

Sulfa cross-reactivity — Furosemide and HCTZ contain a sulfonamide group. Historically, sulfa allergy was considered a contraindication, though current evidence suggests true cross-reactivity is rare. The clinical standard remains to assess allergy history and use clinical judgment. Notify the provider if the patient reports a sulfa allergy before administering.

Fluid and electrolyte monitoring — Weigh patients daily (same time, same scale, same clothing). A gain of more than 2–3 pounds overnight indicates fluid retention. Monitor BMP or CMP for sodium, potassium, BUN, creatinine. Hyponatremia is a common side effect, particularly with thiazides in older adults.

Antiarrhythmics

Cardiac arrhythmias result from disrupted impulse formation or abnormal conduction. Antiarrhythmic drugs work by targeting specific ion channels or receptors to normalize these processes. The Vaughan-Williams classification organizes these drugs into four major classes based on their electrophysiological mechanism.

Vaughan-Williams classification — overview:

Class II and Class IV agents are covered in the antihypertensive sections above. The two Class III agents most likely to appear on NCLEX — amiodarone and adenosine (a non-classified agent) — deserve focused attention.

Amiodarone

Amiodarone is the most complex antiarrhythmic in clinical use. It has properties spanning all four Vaughan-Williams classes — sodium channel blockade, beta-blockade, potassium channel blockade, and calcium channel blockade. This broad mechanism makes it effective against both supraventricular and ventricular arrhythmias, but it also creates a toxicity profile that spans multiple organ systems.

Clinical uses: Ventricular tachycardia, ventricular fibrillation (including ACLS protocols), atrial fibrillation rate and rhythm control. First-line in ACLS for pulseless VT/VF after defibrillation. For the atrial fibrillation clinical context, see the atrial fibrillation nursing guide.

Amiodarone toxicities — multi-organ monitoring table:

Key NCLEX points for amiodarone:

• It has a half-life of 40–55 days — toxicities can persist for months after the drug is stopped
• The pulmonary toxicity is a Black Box Warning — most serious amiodarone complication
• Drug interactions: amiodarone inhibits P-glycoprotein and CYP enzymes, raising levels of warfarin (INR increases — reduce warfarin dose by half) and digoxin (reduce digoxin dose by half)
• Teach patients sun protection (UPF clothing, broad-spectrum sunscreen) from day one

Adenosine

Adenosine is not classified in the Vaughan-Williams system but is the drug of choice for terminating paroxysmal supraventricular tachycardia (SVT). It works by transiently blocking conduction through the AV node, breaking the reentrant circuit responsible for most SVTs.

Half-life: approximately 6 seconds — one of the shortest half-lives of any drug used in clinical practice. This is the pharmacological basis for one of the most technique-dependent nursing skills in cardiac care.

Administration technique — this is where most references stop short:

1. Use a large peripheral vein as proximal to the heart as possible (antecubital preferred). Adenosine must reach the heart before it is metabolized.
2. Draw up adenosine in one syringe and a 20 mL NS flush in a second syringe. Use a stopcock or two-port setup so both can be given in rapid succession.
3. Administer adenosine as a rapid IV bolus — push the full 6 mg dose as fast as possible (literally in 1–2 seconds), then immediately push the saline flush rapidly. The entire sequence must be completed within seconds.
4. Have the patient lie supine before administration. Warn them: “You may feel a brief sensation of chest tightness, flushing, or a feeling of impending doom — this lasts only seconds.” This warning prevents extreme patient distress and is a nursing care standard.
5. Monitor continuous ECG. A brief period of asystole (no electrical activity) or complete heart block lasting 5–15 seconds is expected and does not require intervention — it is the mechanism. Document and observe. If the rhythm does not convert, the dose can be repeated at 12 mg.

Contraindications: Second- or third-degree AV block (without a pacemaker), sick sinus syndrome, known hypersensitivity. Use with caution in asthma (can cause bronchospasm).

Digoxin

Digoxin (Lanoxin) is one of the oldest cardiac drugs still in clinical use, derived from the foxglove plant. It has a narrow therapeutic index — the difference between a therapeutic and a toxic dose is small — which makes it a perennial NCLEX topic and a significant source of preventable adverse events.

Mechanism

Digoxin inhibits the sodium-potassium ATPase (Na/K-ATPase) pump on cardiac myocytes. Normally, this pump moves sodium out of the cell and potassium into the cell. When digoxin blocks this pump:

1. Intracellular sodium rises
2. The sodium-calcium exchanger compensates by pumping sodium out in exchange for calcium in
3. Intracellular calcium rises
4. More calcium is available for each contraction → increased contractile force (positive inotropy)

Simultaneously, digoxin enhances vagal tone at the AV node, slowing conduction — a negative chronotropic effect. This is why digoxin is useful for both conditions it treats: heart failure (needs more force) and atrial fibrillation (needs slower ventricular rate).

Therapeutic range and toxicity threshold

• Therapeutic range: 0.5–2.0 ng/mL (for heart failure, the target is often the lower end: 0.5–0.9 ng/mL)
• Toxic threshold: levels above 2.0 ng/mL are concerning; above 2.4 ng/mL is generally considered toxic
• Critical caveat: toxicity can occur at normal levels if electrolytes are disturbed — particularly hypokalemia

Digoxin toxicity: the hypokalemia connection — mechanistic explanation

This is one of the most important pharmacology concepts on NCLEX, and understanding the mechanism makes it impossible to forget:

The Na/K-ATPase pump — the same pump that digoxin inhibits — has a binding site that potassium and digoxin compete for. When serum potassium is normal, potassium competes effectively at the binding site, limiting how much digoxin can bind. When potassium is low (hypokalemia), there is less competition — digoxin binds more freely to the pump, amplifying its inhibitory effect. The result: the same digoxin dose becomes effectively more potent, and toxicity occurs at drug levels that would be safe in a normokalemic patient.

This is why diuretics and digoxin require careful co-administration monitoring. Furosemide and thiazides both cause hypokalemia — which potentiates digoxin toxicity. Nurses must monitor both the digoxin level AND the potassium level, and treat hypokalemia aggressively in patients taking digoxin.

Hypermagnesemia also potentiates digoxin toxicity through a related mechanism. Monitor magnesium in addition to potassium.

Toxicity signs and symptoms

The classic triad:

1. Gastrointestinal: Nausea, vomiting, anorexia, abdominal pain — often the first symptoms to appear
2. Visual disturbances: Yellow-green visual halos around objects (xanthopsia), blurred vision, photophobia — highly characteristic of digoxin toxicity and NCLEX-testable
3. Cardiac arrhythmias: Any rhythm can occur, but bradyarrhythmias, AV block, and premature ventricular contractions are most common; bidirectional ventricular tachycardia is pathognomonic for digoxin toxicity

Neurological symptoms also occur: headache, fatigue, confusion, dizziness — particularly in older adults, who may present with digoxin toxicity predominantly as altered mental status.

Nursing hold parameters and monitoring

• Hold if heart rate is below 60 bpm — digoxin slows AV conduction and can cause dangerous bradycardia. Check apical pulse for one full minute before every dose.
• Monitor digoxin levels, BMP (potassium, magnesium, creatinine — renal function affects digoxin clearance)
• Assess for early toxicity symptoms at every assessment

Treatment of digoxin toxicity

• Discontinue digoxin
• Correct electrolyte imbalances (particularly hypokalemia and hypomagnesemia)
• Continuous cardiac monitoring
• Digoxin immune fab (Digibind, DigiFab) — the antidote for severe digoxin toxicity. These antibody fragments bind free digoxin molecules, rapidly reducing effective drug levels. Indicated for life-threatening dysrhythmias, severe bradycardia unresponsive to atropine, or serum levels indicating severe toxicity.
• Calcium is contraindicated in digoxin toxicity — IV calcium can worsen cardiac contractility abnormalities and may precipitate fatal arrhythmias.

Drug interactions raising digoxin levels

Both quinidine and amiodarone inhibit renal P-glycoprotein transport, which is responsible for digoxin excretion. When either drug is added to a digoxin regimen, digoxin levels can double. Standard practice: reduce the digoxin dose by 50% when starting amiodarone or quinidine, and recheck levels closely.

Nursing monitoring quick reference

NCLEX high-yield bullets

These are the most testable facts from this reference — the ones that appear repeatedly on NCLEX and in clinical practice:

• ACE inhibitor dry cough is caused by bradykinin accumulation — not an allergy. Clinical response: switch to an ARB.
• ACE inhibitor angioedema is a permanent discontinuation. Do not restart, do not switch doses — assess airway and escalate.
• Beta-blockers: NEVER stop abruptly. Rebound tachycardia, hypertension, and MI are the consequences. Taper under supervision.
• Beta-blockers mask hypoglycemia symptoms in diabetics — except diaphoresis. Teach patients to check blood glucose, not rely on symptoms.
• Metoprolol and carvedilol are evidence-based for stable HF — but hold in decompensated HF.
• Furosemide ototoxicity: risk increases with high-dose IV, rapid infusion, and aminoglycoside co-administration. Max infusion rate: 4 mg/min.
• Grapefruit inhibits CYP3A4 — increases calcium channel blocker levels. Applies to all CCBs.
• Verapamil or diltiazem + beta-blocker = dangerous combination — high risk of AV block and severe bradycardia.
• Amiodarone monitoring: baseline and annual CXR, TFTs every 6 months, LFTs every 6 months, eye exam annually. Half-life is 40–55 days — toxicity persists after stopping.
• Amiodarone raises warfarin levels (reduce warfarin by ~50%) and raises digoxin levels (reduce digoxin by ~50%).
• Digoxin therapeutic range: 0.5–2.0 ng/mL. Hold for HR <60. Know this range.
• Hypokalemia potentiates digoxin toxicity — mechanistically, because potassium competes with digoxin at the Na/K-ATPase binding site. Treat hypokalemia aggressively in patients on digoxin.
• Digoxin toxicity triad: nausea/vomiting/anorexia + yellow-green visual halos + cardiac arrhythmias.
• Digoxin antidote: Digibind (digoxin immune fab). Calcium is contraindicated.
• Adenosine half-life: ~6 seconds. Must be given as a rapid IV bolus followed immediately by a rapid NS flush. Use a large proximal vein. Transient asystole is expected.

Drug interaction quick reference

Further reading

This reference is part of the pharmacology pillar. Continue building your clinical pharmacology knowledge with:

• Psychiatric medications nursing reference — antipsychotics, mood stabilizers, lithium monitoring
• Drug classifications nursing guide — prefix and suffix patterns across all drug classes
• Heart failure nursing reference — clinical application of the cardiac drugs covered above
• Atrial fibrillation nursing guide — amiodarone, digoxin, and rate control in clinical context
• Electrolyte imbalances nursing reference — hypokalemia, hypomagnesemia, and their cardiovascular consequences