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Antihypertensives

5 min read

Antihypertensives

Key Points

  • Six major classes: ACE inhibitors, ARBs, beta-blockers, calcium channel blockers, thiazide diuretics, and direct vasodilators
  • ACE inhibitors: Hallmark adverse effect is persistent dry cough; both ACE inhibitors and ARBs are contraindicated in pregnancy (fetal harm/death — Boxed Warning)
  • Beta-blockers: Hold if apical HR <60 bpm; NEVER stop abruptly — taper over 1–2 weeks
  • Angioedema from ACE inhibitors = life-threatening emergency — stop drug immediately
  • Patients commonly take multiple antihypertensives that work synergistically on different mechanisms

Drug Class Overview

Antihypertensives are medications that lower elevated blood pressure. Hypertension is a major risk factor for myocardial infarction, stroke, heart failure, and renal disease. Multiple classes target different points in blood pressure regulation — most patients with Stage 2 hypertension (≥140/90 mm Hg) require combination therapy with complementary mechanisms.

Major Classes

ACE Inhibitors (Angiotensin-Converting Enzyme Inhibitors)

Mechanism: Block conversion of Angiotensin I → Angiotensin II in the RAAS system → vasodilation + reduced aldosterone release → decreased sodium/water retention.

Examples: Captopril, lisinopril, enalapril, ramipril, benazepril (suffix: “-pril”).

Indications: Hypertension, heart failure, diabetic nephropathy (slow progression), post-myocardial infarction.

Adverse Effects:

  • Persistent dry cough (most common, 10–15% of patients; due to bradykinin accumulation) — if intolerable, switch to ARB
  • Hyperkalemia — avoid potassium supplements and salt substitutes
  • Angioedema (rare but life-threatening) — facial/tongue swelling, difficulty breathing → STOP drug, call 911, epinephrine ready
  • Hypotension (especially first dose), proteinuria

ACE Inhibitor Pregnancy Contraindication — Boxed Warning

ACE inhibitors cause fetal renal damage and fetal/neonatal death when administered in the 2nd and 3rd trimesters. Discontinue immediately if patient becomes pregnant. Counsel all women of childbearing age.

ARBs (Angiotensin II Receptor Blockers)

Mechanism: Block Angiotensin II receptors → vasodilation and reduced aldosterone → similar effect to ACE inhibitors but without bradykinin accumulation.

Examples: Losartan, valsartan, irbesartan, olmesartan (suffix: “-sartan”).

Key Difference from ACE Inhibitors: ARBs do NOT cause the persistent cough — preferred for ACE inhibitor-intolerant patients.

Adverse Effects: Hypotension, dizziness, hyperkalemia, angioedema (less common than ACE inhibitors), proteinuria.

Boxed Warning: Contraindicated in pregnancy — same risk as ACE inhibitors.

ARB + ACE Inhibitor Combination

Combining ACE inhibitors and ARBs increases risk of hypotension, hyperkalemia, and renal impairment without additional blood pressure benefit. Generally avoid dual RAAS blockade.

Beta-Blockers (Beta-1 Selective Antagonists)

Mechanism: Block beta-1 adrenergic receptors in the heart → decreased heart rate and contractility → decreased cardiac output and blood pressure.

Examples: Metoprolol (selective beta-1), atenolol, bisoprolol; carvedilol (non-selective beta-1/beta-2/alpha).

Indications: Hypertension, heart failure, post-MI, atrial fibrillation (rate control), angina.

Key Nursing Points:

  • Check apical pulse before administration — hold and notify provider if HR <60 bpm (unless alternate parameters specified)
  • Do NOT crush extended-release (ER) formulations (metoprolol succinate)
  • Monitor blood glucose in diabetics: Beta-blockers mask tachycardia (key sign of hypoglycemia); glycemic control monitoring essential
  • NEVER stop abruptly: Taper over 1–2 weeks — abrupt discontinuation → rebound hypertension, chest pain, or MI

Adverse Effects: Bradycardia, fatigue, depression, insomnia, erectile dysfunction, cold extremities, bronchoconstriction (at high doses or non-selective agents — use caution in asthma/COPD).

Calcium Channel Blockers (CCBs)

Mechanism: Block calcium channels in vascular smooth muscle and cardiac tissue → smooth muscle relaxation → vasodilation → decreased BP and decreased cardiac workload.

Examples:

  • Dihydropyridines (primarily vascular; preferred for HTN): Amlodipine, nifedipine, felodipine
  • Non-dihydropyridines (cardiac + vascular; also used for arrhythmias): Verapamil, diltiazem

Adverse Effects: Peripheral edema (especially dihydropyridines), headache, flushing, reflex tachycardia (nifedipine). Verapamil → constipation, bradycardia.

Interaction: Verapamil and diltiazem inhibit CYP3A4 → increased levels of many drugs including statins, macrolides.

Thiazide Diuretics — See diuretics

Hydrochlorothiazide (HCTZ) is a first-line antihypertensive (see diuretics.md for details). Frequently combined with ACE inhibitors or ARBs. Key risk: hypokalemia.

Direct Vasodilators

Hydralazine: Direct relaxation of arterial smooth muscle → vasodilation.

Indications: Hypertension (severe/refractory), hypertensive emergency in pregnancy (eclampsia), heart failure (with isosorbide dinitrate).

Adverse Effects: Drug-induced systemic lupus erythematosus (SLE) — butterfly facial rash, joint pain, fever. Monitor CBC and antinuclear antibody (ANA) titers. Orthostatic hypotension, palpitations, headache.

Alpha-2 Agonists

Clonidine: Stimulates central alpha-2 receptors → decreased sympathetic outflow → vasodilation and decreased peripheral resistance.

Adverse Effects: Sedation, dry mouth, bradycardia, orthostatic hypotension.

Critical: Do NOT stop abruptly → rebound hypertension (potentially severe).

Nursing Assessment

Before Administration:

  • Obtain BP and apical HR — compare to parameters; hold for BP <90/60 or HR <60 (unless other orders)
  • Review current medications for interactions (especially potassium with ACE inhibitors/ARBs)
  • Assess for pregnancy (ACE inhibitors and ARBs: teratogenic)
  • Review renal function (many antihypertensives affect renal clearance)

Ongoing Monitoring:

  • BP trend (lying, sitting, standing for orthostatic hypotension)
  • Serum potassium — hyperkalemia risk with ACE inhibitors, ARBs, potassium-sparing diuretics
  • Peripheral edema — especially with CCBs
  • Angioedema: swelling of face, lips, tongue, throat → emergency response
  • Persistent cough → report; may require switch from ACE inhibitor to ARB

Patient Education:

  • Take at the same time each day; never skip or double dose
  • Rise slowly from bed/chair to prevent orthostatic dizziness
  • Beta-blockers: never stop without tapering under provider guidance
  • ACE inhibitors/ARBs: avoid salt substitutes (contain potassium) and NSAIDs (decrease effectiveness, increase renal risk)
  • Clonidine patch: apply to hairless skin; rotate sites; never stop abruptly
  • Monitor home BP and maintain medication log

Self-Check

  1. A patient on lisinopril develops a persistent dry cough. What alternative drug class provides similar mechanism but without the cough?
  2. Before administering metoprolol, the patient’s apical heart rate is 54 bpm. What is the nurse’s priority action?
  3. A patient on an ACE inhibitor reports sudden swelling of the lips and difficulty swallowing. What is this reaction, and what is the immediate nursing response?

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