Pharmacology Flashcards: ACE Inhibitors, ARBs, Beta Blockers, Calcium Channel Blockers

Angiotensin-converting enzyme inhibitors, or ACE inhibitors, lower blood pressure by blocking the enzyme that converts angiotensin one to angiotensin two, a potent vasoconstrictor. Without angiotensin two, blood vessels relax and blood volume decreases. Common ACE inhibitors include lisinopril, enalapril, ramipril, and captopril, all ending in the suffix "pril." They are first-line treatment for hypertension, heart failure, and diabetic nephropathy. The most distinctive side effect is a persistent dry cough caused by bradykinin accumulation, which occurs in up to 20 percent of patients.

The most common side effect of ACE inhibitors is a persistent dry cough, occurring in 5 to 20 percent of patients. It happens because ACE inhibitors prevent the breakdown of bradykinin, a peptide that accumulates in the lungs and irritates airway sensory nerves. The cough is nonproductive, often worse at night, and resolves within one to four weeks after discontinuing the medication. Patients who cannot tolerate the cough are typically switched to an angiotensin two receptor blocker, or ARB, which does not affect bradykinin levels and rarely causes cough.

Angiotensin two receptor blockers, or ARBs, lower blood pressure by blocking the angiotensin two receptor directly rather than preventing its formation. Common ARBs include losartan, valsartan, irbesartan, and candesartan, all ending in the suffix "sartan." ARBs produce similar blood pressure reduction as ACE inhibitors but rarely cause the dry cough because they do not increase bradykinin levels. ARBs are prescribed for hypertension, heart failure, and diabetic kidney disease, especially for patients who developed a cough on ACE inhibitors. ACE inhibitors and ARBs should not be used together.

Beta blockers work by blocking beta-adrenergic receptors, reducing heart rate, cardiac output, and blood pressure. Common beta blockers include metoprolol, atenolol, propranolol, and carvedilol. They are used for hypertension, angina, heart failure, arrhythmias, migraine prevention, and anxiety-related tremor. Beta-1 selective agents like metoprolol and atenolol primarily affect the heart, while nonselective agents like propranolol also block beta-2 receptors in the lungs and can worsen asthma. The suffix "olol" identifies most beta blockers.

Selective beta blockers, also called cardioselective, primarily block beta-1 receptors in the heart, reducing heart rate and contractility without significantly affecting beta-2 receptors in the lungs and blood vessels. Metoprolol and atenolol are selective. Nonselective beta blockers like propranolol and nadolol block both beta-1 and beta-2 receptors, which can cause bronchospasm in patients with asthma or chronic obstructive pulmonary disease. Selectivity is dose-dependent and diminishes at higher doses.

Calcium channel blockers prevent calcium from entering smooth muscle cells of blood vessels and cardiac muscle, causing vasodilation and reducing blood pressure. The two main types are dihydropyridines and nondihydropyridines. Dihydropyridines like amlodipine and nifedipine primarily relax blood vessels with minimal heart rate effect, identified by the suffix "dipine." Nondihydropyridines like verapamil and diltiazem also slow heart rate and reduce cardiac contractility, making them useful for arrhythmias.

ACE inhibitors and ARBs are contraindicated in pregnancy because they can cause fetal renal damage, oligohydramnios meaning low amniotic fluid, skull defects, lung hypoplasia, and fetal death, particularly in the second and third trimesters. These drugs cross the placenta and disrupt the fetal renin-angiotensin system, which is essential for normal kidney development and blood pressure regulation in the fetus.

Angioedema is a rapid, potentially life-threatening swelling of deep tissue, most commonly affecting the face, lips, tongue, and throat, which can obstruct the airway. ACE inhibitors are the most common medication cause, occurring in approximately 0.1 to 0.7 percent of patients, with higher rates in Black patients. It can occur at any time during treatment, even after years of use. The mechanism involves bradykinin accumulation. ARBs cause angioedema much less frequently but are still used cautiously in patients with a history of ACE inhibitor angioedema.

Cardiovascular drug suffixes are a reliable way to identify drug classes on exams. ACE inhibitors end in "pril" such as lisinopril and enalapril. ARBs end in "sartan" such as losartan and valsartan. Beta blockers end in "olol" such as metoprolol and atenolol. Dihydropyridine calcium channel blockers end in "dipine" such as amlodipine and nifedipine. Statin cholesterol drugs end in "statin" such as atorvastatin and rosuvastatin. Learning these suffixes allows you to identify the drug class, mechanism, side effects, and contraindications for any unfamiliar medication name on the exam.

Before giving a beta blocker, assess heart rate and blood pressure. Hold the medication and notify the provider if the heart rate is below 60 beats per minute or systolic blood pressure is below 90 millimeters of mercury. Teach patients to rise slowly to prevent orthostatic hypotension and to monitor their pulse daily. Never discontinue beta blockers abruptly because sudden withdrawal can cause rebound tachycardia, hypertensive crisis, or myocardial ischemia. Taper the dose gradually over one to two weeks. ---