Cardiovascular Drugs

Cardiovascular drugs manage the chronic diseases that fill a clinic by acting on two control systems — the autonomic nervous system for moment-to-moment regulation and the renin–angiotensin–aldosterone system for long-term hormonal control — so once you can name a class's target you can predict its clinical effect, its characteristic adverse reaction and its one contraindication.

Objectives: identify the major classes of cardiovascular drugs; describe the general mechanism of action of each class and how it influences cardiovascular physiology; explain the basic pharmacokinetic and pharmacodynamic properties of the key classes; discuss the relationship between receptor targets and clinical effects; recognize the common adverse drug reactions associated with each class and understand their clinical significance; and compare the contraindications and precautions relevant to specific classes.

Why cardiovascular drugs matter

A very large share of chronic disease is cardiovascular, and each condition drags its own drug classes with it: hypertension, lipid disorders, arrhythmias, heart failure, myocardial infarction, and the antiplatelet and anticoagulant needs that follow from all of them.

The high-yield frame is five slots, and every class below is presented in exactly those five: drug class, mechanism of action, clinical use, adverse drug reactions, contraindications and precautions. Learn each class as a five-slot card and the material collapses to something memorable.

Learn every class in the same five slots. Class → mechanism → clinical use → adverse drug reaction → contraindication. That is the shape of the material and of the questions.

The major classes at a glance

The classes are organized by the problem they solve. Notice how often one appears under several: beta blockers are antihypertensives, heart failure drugs, antianginals and antiarrhythmics at once, because the same β₁ blockade helps in each setting.

Problem	Class	Mechanism	Examples
Hypertension	Diuretics	Increase sodium and water excretion, lowering plasma volume	Hydrochlorothiazide
Hypertension	ACE inhibitors; ARBs	Block the ACE step; block the AT₁ receptor	Lisinopril; losartan
Hypertension	Beta blockers	Block β₁: rate, contractility, renin	Propranolol
Hypertension	Calcium channel blockers	Block L-type calcium entry	Amlodipine
Hypertension	Vasodilators	Relax vascular smooth muscle directly	Hydralazine
Heart failure	ACEi, ARBs, ARNI	Suppress RAAS vasoconstriction and sodium retention	Lisinopril, losartan, sacubitril/valsartan
Heart failure	Beta blockers; diuretics	Blunt sympathetic drive; remove congestive volume	Carvedilol, metoprolol succinate; furosemide, torsemide
Heart failure	Aldosterone antagonists	Block the aldosterone receptor	Spironolactone, eplerenone
Heart failure	Positive inotropes	Increase force of contraction	Digoxin, dopamine, dobutamine, norepinephrine, epinephrine
Angina	Nitrates	Nitric oxide donation relaxes vessels	Nitroglycerin, isosorbide mononitrate
Arrhythmia	Classes I, II, III, IV	Sodium, beta, potassium, calcium channel blockade	Quinidine, lidocaine, flecainide; metoprolol, esmolol; amiodarone, sotalol; verapamil, diltiazem
Lipid disorders	Statins	HMG-CoA reductase inhibition lowers LDL	Atorvastatin, rosuvastatin, simvastatin
Lipid disorders	Fibrates; niacin	Lower triglycerides	Gemfibrozil, fenofibrate; niacin (vitamin B3)
Lipid disorders	Absorption inhibitors; PCSK9 inhibitors	Reduce intestinal absorption; increase LDL receptor recycling	Ezetimibe; alirocumab, evolocumab
Thrombosis	Anticoagulants	Inhibit the clotting cascade	Warfarin, heparin, enoxaparin, apixaban, rivaroxaban
Thrombosis	Antiplatelets; thrombolytics	Inhibit aggregation; break down formed clot	Aspirin, clopidogrel, ticagrelor; alteplase, tenecteplase

Four naming stems carry most of the recognition load: -olol is a beta blocker, -pril an ACE inhibitor, -sartan an ARB, -statin an HMG-CoA reductase inhibitor.

Read the table sideways. The classes appearing under several problems — beta blockers, calcium channel blockers, diuretics, ACE inhibitors and ARBs — deserve the most study time: one mechanism buys four or five clinical answers.

How blood pressure is controlled

Almost every antihypertensive uses one of two levers, often both: reducing cardiac output and/or decreasing peripheral vascular resistance. Two systems set those variables — the autonomic nervous system for moment-to-moment regulation and the renin–angiotensin–aldosterone system for long-term hormonal control. Both are triggered by a fall in blood pressure and both push it back up.

The sympathetic arm. A drop in pressure raises sympathetic activity, activating β₁ adrenoceptors on the heart (raising cardiac output), α₁ adrenoceptors on smooth muscle (raising venous return and peripheral resistance), and β₁ adrenoceptors on the kidney (releasing renin). All three arrows converge on a rise in blood pressure.

The RAAS arm. The same drop reduces renal blood flow and glomerular filtration rate, increasing renin release. Renin converts angiotensinogen, an α₂-globulin in blood, to inactive angiotensin I; ACE converts that to angiotensin II, which increases sympathetic output, constricts vascular smooth muscle and stimulates aldosterone. Aldosterone drives sodium and water retention, raising blood volume and therefore blood pressure.

Every RAAS drug is named for the step it interrupts: renin inhibitors the first step, ACE inhibitors the conversion of angiotensin I to II, ARBs angiotensin II at its receptor, aldosterone receptor antagonists the final hormonal step. The mechanism of action is the name of the drug.

Aldosterone means sodium, water, volume. Aldosterone → sodium and water retention → increased blood volume → increased blood pressure. Every aldosterone antagonist and every diuretic works by reversing that chain.

Treatment strategies

The point of treating hypertension is not the number — the goal is to reduce cardiovascular and renal morbidity and mortality. For most patients the target is systolic below 130 mmHg and diastolic below 80 mmHg. Which drug you start with varies by guideline and by patient.

Guideline	Population	Goal	Initial therapy
ACC/AHA 2017	General, and over 65	<130/80	Nonblack: thiazide, ACEi, ARB or CCB. Black: thiazide or CCB
ADA 2021	Diabetes	<140/90; <130/80 if high ASCVD risk	ACE inhibitor or ARB
KDIGO 2020	Chronic kidney disease	Systolic <120	ACE inhibitor or ARB
ESH/ESC 2018	Under 65; over 65 or CKD	<130/80; 130–139/70–79	ACEi or ARB plus a CCB or a thiazide
NICE 2019	Over 80; under 80	<150/90; <140/90	55 or older, or Black: CCB. Under 55: ACEi or ARB

Concomitant disease narrows the choice further. Stable ischemic heart disease points to beta blockers, ACE inhibitors, ARBs or CCBs; diabetes to those plus diuretics; recurrent stroke to diuretics, ACE inhibitors or ARBs; heart failure and previous myocardial infarction to beta blockers, ACE inhibitors, ARBs and aldosterone-receptor antagonists, with diuretics added in heart failure; and chronic kidney disease to ACE inhibitors or ARBs.

Diuretics

Examples: thiazides, loop diuretics, potassium-sparing agents. Clinical indication: hypertension, heart failure, pulmonary edema, renal impairment, cirrhosis.

Mechanism of action: increase sodium and water excretion → decreased plasma volume → decreased blood pressure. A thiazide reduces sodium and water retention, lowering blood volume and cardiac output, and also lowers peripheral resistance; both arrows end at a fall in blood pressure. Pharmacokinetics and pharmacodynamics: onset in hours, renally excreted. Receptor target: sodium transporters in the nephron segments.

Adverse drug reactions: electrolyte imbalances — with loop diuretics, hypokalemia — plus dehydration and hypotension. Contraindications: severe renal failure (loop diuretics with caution) and sulfa allergy with thiazides.

Water always follows sodium. That is why the target is a sodium transporter but the effect is water excretion — and why the predictable harm is an electrolyte problem.

Beta blockers

Examples: metoprolol, propranolol, carvedilol. Clinical indication: hypertension, heart failure, angina, arrhythmias, post-myocardial infarction, migraine prophylaxis.

Mechanism of action: block β₁ → decreased heart rate, contractility and renin release. Follow both branches: β₁ blockade on the heart lowers cardiac output, and on the kidney it lowers renin, which lowers angiotensin II and therefore peripheral resistance, aldosterone, sodium and water retention and blood volume. A beta blocker is a RAAS drug through the back door.

Pharmacokinetics: hepatic metabolism, variable lipophilicity. Pharmacodynamics: dose-dependent reduction in heart rate and blood pressure — which is why too high a dose slows the heart too much. Receptor target: β₁ in the heart, β₂ in the lungs.

Adverse drug reactions: hypotension, bradycardia, fatigue, bronchospasm with nonselective agents, insomnia, dizziness. Contraindications: asthma, severe bradycardia. Nomenclature: -olol.

The counting trick: you have one heart (β₁) and two lungs (β₂). A nonselective drug hits both receptors and so affects both organs; a β₁-selective drug has much less effect on the lungs. That single idea is why nonselective agents are the ones feared in asthmatic patients.

Generations track exactly what the drug blocks; a mnemonic for them in order is "PRO – BAM – CARLAB".

Generation	Blocks	Agents
1st	β₁ and β₂	Propranolol
2nd	β₁	Bisoprolol, atenolol, metoprolol
3rd	β plus α₁	Carvedilol (dilates blood vessels), labetalol (the "a" is for alpha blocker)

The third-generation logic: alpha receptors sit on vessels, so α₁ blockade produces vasodilation, which would normally trigger reflex tachycardia — but the β₁-blocking activity in the same molecule prevents it.

Cardioselective (β₁)	No selectivity (β₁ and β₂)
Nebivolol, esmolol, betaxolol, bisoprolol, atenolol, acebutolol, metoprolol	Carteolol, carvedilol, labetalol, nadolol, penbutolol, pindolol, propranolol, sotalol, timolol

The cardioselective list spells out Newer Exclusive Beta-blockers Are Acting Mainly cardioselective. In the nonselective column, carvedilol and labetalol also have α₁ blockade. Propranolol is also used for thyroid storm, migraine prophylaxis, anxiety and alcohol withdrawal.

⭐ Nonselective beta blockade plus asthma is the classic harm. β₂ blockade causes bronchospasm, so asthma is the contraindication and a cardioselective agent is the way around it. The other precaution is diabetes, where beta blockade masks the warning signs of hypoglycemia.

ACE inhibitors and ARBs

ACE inhibitors: lisinopril, enalapril. ARBs: losartan, valsartan. Both are RAAS drugs, and in both cases the name states the mechanism.

Clinical indication: hypertension, heart failure, post-myocardial infarction, diabetic nephropathy. Mechanism of action: block RAAS → decreased vasoconstriction and sodium retention. Pharmacokinetics: renally cleared, long half-life. Pharmacodynamics: decreased afterload and preload.

Adverse drug reactions: cough (ACE inhibitors specifically), hyperkalemia, an increase in serum creatinine, hypotension, altered taste, angioedema. Contraindications: pregnancy, bilateral renal artery stenosis. Nomenclature: -pril and -sartan.

The bradykinin story. ACE has a second job: it also breaks down bradykinin. Inhibit ACE and bradykinin accumulates. Bradykinin leads to vasodilation, contributing to the antihypertensive effect — and it also contributes to the cough. That is why the dry cough and angioedema are characteristic of ACE inhibitors: an ARB blocks the receptor downstream and never touches bradykinin metabolism, so cough occurs at essentially placebo rates and angioedema far less often — less often, but not never, since every ARB label carries an angioedema warning.

⭐ Bradykinin is the whole reason ARBs exist as a separate class. Same RAAS blockade, no bradykinin accumulation, no cough. Both classes still share hyperkalemia, the rise in creatinine, and the contraindication in pregnancy.

Calcium channel blockers

Examples: amlodipine, diltiazem, verapamil. Clinical indication: hypertension, angina, arrhythmias.

Mechanism of action: block calcium entry → decreased vascular tone and contractility. The arrhythmia use follows from the same idea: calcium movement is what creates the abnormal rhythm, so block it and the arrhythmia stops.

Targets: L-type calcium channels in cardiac and smooth muscle. Adverse drug reactions: edema, constipation, bradycardia with the non-dihydropyridines, flushing, dizziness, hypotension, headache. Contraindication: severe heart failure, specifically with verapamil.

The agents are not interchangeable. Nifedipine has little effect on AV conduction, while verapamil and diltiazem both decrease it — making the non-dihydropyridines useful for rate control and dangerous in a patient already bradycardic or in heart block. Adverse effects were also more frequent with nifedipine at 18% than verapamil at 9% or diltiazem at 2%.

⭐ Vessel drug or node drug. A dihydropyridine (amlodipine, nifedipine) works on the vessel: peripheral edema and flushing. A non-dihydropyridine (verapamil, diltiazem) works on the node: bradycardia, heart block, constipation — and verapamil is the one contraindicated in severe heart failure.

Lipid-lowering agents

Coronary heart disease is correlated with abnormal cholesterol levels — dyslipidemia. The pattern that matters is elevated LDL cholesterol and triglycerides together with low HDL cholesterol.

Statins are HMG-CoA reductase inhibitors and they lower LDL. The mechanism runs in four steps, because the fall in serum LDL is indirect:

1. Statins inhibit HMG-CoA reductase, the enzyme converting HMG-CoA to mevalonic acid, decreasing cholesterol within the cell.
2. Low intracellular cholesterol stimulates synthesis of LDL receptors.
3. More LDL receptors promote uptake of LDL from the blood — this is where serum LDL falls.
4. Low intracellular cholesterol also decreases secretion of VLDL.

Pharmacokinetics: hepatic metabolism. Adverse drug reactions: myopathy and elevated liver function tests. Contraindications: pregnancy and liver disease. Nomenclature: -statin.

The other lipid classes each attack a different point: fibrates lower triglycerides, ezetimibe reduces intestinal absorption, PCSK9 inhibitors increase LDL receptor recycling, and niacin is also used.

Faculty vs current practice. This course lists pregnancy and liver disease as the statin contraindications, and pregnancy is what to answer on the exam. In July 2021 the FDA requested removal of the blanket pregnancy contraindication from statin labeling; current labeling advises discontinuing a statin in most pregnant patients rather than forbidding it outright, while liver disease is unchanged. Know both; answer pregnancy.

Three L's for statins: Lipid Lowering, Liver. The liver is where they are metabolized, liver disease is a contraindication, and elevated liver function tests are the monitoring problem — alongside myopathy, the muscle complaint you must take seriously.

Antiarrhythmics

The Vaughan Williams classes are organized by which ion channel is blocked and which phase of the cardiac action potential is affected.

Class	Mechanism	Drugs	Adverse effects
IA	Sodium channel blocker — slows phase 0 depolarization	Disopyramide, procainamide, quinidine	QT prolongation, ventricular arrhythmias, acute heart failure, anticholinergic effects. Quinidine: cinchonism. Procainamide: lupus-like syndrome
IB	Sodium channel blocker — shortens phase 3 repolarization	Lidocaine, mexiletine	Worsening ventricular arrhythmias, tremor, ataxia, paresthesia, confusion, seizures
IC	Sodium channel blocker — markedly slows phase 0	Flecainide, propafenone	Bradycardia, QT prolongation, worsening ventricular arrhythmias, acute heart failure; propafenone bronchospasm
II	β-adrenoreceptor blocker — inhibits phase 4 depolarization in the SA and AV nodes	Atenolol, esmolol, metoprolol	Bradycardia, heart block, hypotension, worsening heart failure, bronchospasm, fatigue
III	Potassium channel blocker — prolongs phase 3 repolarization	Amiodarone, dofetilide, dronedarone, sotalol	Amiodarone: QT prolongation, pulmonary toxicity (pneumonitis, fibrosis), hepatic failure, neuropathy, hypo- and hyperthyroidism, blue-gray skin, corneal deposits
IV	Calcium channel blocker — inhibits the action potential in the SA and AV nodes	Diltiazem, verapamil	Bradycardia, heart block, acute heart failure, peripheral edema; verapamil gingival hyperplasia and constipation
Other	Various mechanisms	Adenosine, digoxin, magnesium sulfate, ranolazine	Adenosine: transient arrhythmias, chest pain, dyspnea. Digoxin: bradycardia, potassium disturbance, anorexia, xanthopsia. Ranolazine: QT prolongation

Which arrhythmia gets which drug. Atrial fibrillation and flutter are treated with metoprolol, propafenone, verapamil, diltiazem, digoxin, amiodarone or dofetilide, plus anticoagulant therapy; beta blockers are used because they decrease heart rate and promote conversion to sinus rhythm, and long-term oral anticoagulation reduces the stroke risk. Atrial fibrillation involves multiple ectopic atrial foci creating chaotic impulses; the ventricular response may be rapid, in the range of 100–150 beats per minute, and irregular, so cardiac output falls. In supraventricular tachycardia, AV nodal conduction is slowed with metoprolol, verapamil or digoxin, and acute episodes also respond to adenosine or diltiazem. Ventricular tachycardia is treated with lidocaine or amiodarone, and ventricular fibrillation not responding to defibrillation with lidocaine, amiodarone or epinephrine. Ventricular tachycardia is a common cause of death after myocardial infarction because cardiac output is impaired and the rhythm may degenerate into ventricular fibrillation.

⭐ Amiodarone is a whole-body drug. It works in nearly every rhythm and injures nearly every organ: lung, thyroid in both directions, liver, nerve, eye and skin. No other antiarrhythmic carries that pattern.

Heart failure agents

Heart failure is treated with five groups at once, each doing something different to the same pump.

Group	Agents	What it does
ACE inhibitors, ARBs, ARNI	Lisinopril, losartan, sacubitril/valsartan	Interrupt RAAS vasoconstriction and sodium retention, lowering preload and afterload
Beta blockers	Carvedilol, metoprolol succinate	Blunt the chronic sympathetic drive that worsens the failing heart
Diuretics	Furosemide, torsemide	Remove the volume responsible for congestion and pulmonary edema
Aldosterone antagonists	Spironolactone, eplerenone	Block the last hormonal step in sodium and water retention
Positive inotropes	Digoxin, dopamine, dobutamine, norepinephrine, epinephrine	Increase the force of contraction

Digoxin deserves separate attention. It is a positive inotrope, it also slows AV nodal conduction in atrial fibrillation and supraventricular tachycardia, it requires renal dose adjustment, and its toxicity is distinctive: bradycardia, worsening ventricular arrhythmias, potassium disturbances in either direction, anorexia, hallucinations, blurred vision and xanthopsia — a yellow-green tint to vision.

⭐ Xanthopsia is digoxin until proven otherwise. Yellow-tinged vision with nausea, anorexia and a slow rhythm in heart failure or atrial fibrillation is the classic picture, and impaired renal function is the usual reason the level climbed.

Vasodilators, nitrates and antianginals

Examples: nitroglycerin, hydralazine. Clinical indication: heart failure.

Mechanism: increased nitric oxide → smooth muscle relaxation, vasodilation and reduced afterload. The cascade runs administered nitrates → nitrites → nitric oxide → cGMP → dephosphorylation of myosin light chain → vascular smooth muscle relaxation. Every step is an increase and the endpoint is a relaxed vessel.

Pharmacokinetics: rapid onset with sublingual nitroglycerin. Adverse drug reactions: headache, hypotension, reflex tachycardia, palpitations, angina, nausea.

Contraindication: concurrent use of a phosphodiesterase-5 inhibitor such as sildenafil. A PDE-5 inhibitor is itself a potent vasodilator; give nitroglycerin on top of it and the patient's blood pressure bottoms out. This is not a soft caution — it is the interaction to ask about before handing anyone a nitrate.

Choosing an antianginal. Angina is treated with beta blockers, calcium channel blockers, long-acting nitrates and ranolazine, and the comorbidity decides which is preferred. Beta blockers are preferred after a recent myocardial infarction and in heart failure with reduced ejection fraction, but generally avoided in vasospastic angina, where the calcium channel blocker is the preferred agent and a long-acting nitrate is a neutral, acceptable option — the problem there is spasm, and a beta blocker does not relieve spasm. When hypertension coexists, beta blockers and calcium channel blockers are both preferred; in heart failure with reduced ejection fraction a dihydropyridine is acceptable but a non-dihydropyridine is generally avoided. In asthma, nonselective beta blockers are avoided and selective agents used with close monitoring.

Faculty vs current practice. This course describes the nitrate effect as vasodilation with reduced afterload, and that is the answer to give here. Standard pharmacology teaches that nitrates at therapeutic doses dilate veins preferentially, so the dominant hemodynamic effect is reduced preload — less venous return, less ventricular wall tension, less myocardial oxygen demand — while hydralazine is the arterial dilator that reduces afterload. A boards-style stem asking how nitrates relieve angina expects preload reduction; know both.

⭐ Ask about sildenafil before you give a nitrate. Two vasodilators on the same nitric oxide–cGMP pathway produce profound, sometimes fatal hypotension. Headache, by contrast, is the expected nitrate effect.

Antiplatelets and anticoagulants

Antiplatelets — aspirin, clopidogrel, ticagrelor — inhibit platelet aggregation; aspirin's mechanism is COX-1 inhibition. Anticoagulants — heparin, warfarin and the direct oral anticoagulants — inhibit the clotting cascade. Thrombolytics — alteplase, tenecteplase — break down clot that has already formed.

Adverse drug reactions: bleeding across the board, plus thrombocytopenia with heparin. Contraindications: active bleeding and hemorrhagic stroke — the patient is already bleeding, so do not make it worse.

Agent	Adverse effects	Key interactions	Monitoring
Aspirin	Angioedema, bleeding, bronchospasm, GI disturbance, Reye syndrome	Anticoagulants, P2Y12 inhibitors and NSAIDs increase bleeding; methotrexate toxicity rises	CBC, LFT
Clopidogrel	Bleeding, Stevens-Johnson syndrome	Strong CYP2C19 inhibitors such as omeprazole reduce the antiplatelet effect	CBC, LFT
Ticagrelor	Bleeding, dyspnea, headache, elevated serum creatinine	CYP3A4 inhibitors (ketoconazole) increase bleeding; inducers (rifampin) reduce efficacy	CBC, LFT

Of the remaining oral agents, prasugrel adds headache and hypertension, cilostazol adds peripheral edema and must be given on an empty stomach, and dipyridamole needs no routine monitoring. The injectable agents — abciximab, eptifibatide and tirofiban — share hypotension, nausea, vomiting and thrombocytopenia, and are followed with aPTT, hemoglobin and hematocrit, platelet count and thrombin time.

⭐ Clopidogrel plus omeprazole is the interaction to recognize. Omeprazole inhibits CYP2C19 and clopidogrel needs CYP2C19 to work, so the combination leaves the patient less protected — therapeutic failure, not toxicity.

Drugs used to treat bleeding

When an anticoagulated patient bleeds, the antidote is chosen by the drug that caused it.

Antidote	Reason for bleeding	Adverse effects	Monitoring
Aminocaproic acid, tranexamic acid	Fibrinolytic state	Muscle necrosis, thrombosis, cerebrovascular accident, seizure	CBC, muscle enzymes, blood pressure
Factor Xa reversal agent	Apixaban, rivaroxaban	Thrombosis, myocardial infarction	None necessary per the manufacturer
Idarucizumab	Dabigatran	Hypokalemia, thrombosis	aPTT, clotting time, thrombin time
Protamine sulfate	Heparin	Flushing, nausea and vomiting, dyspnea, bradyarrhythmia, hypotension, anaphylaxis	Coagulation monitoring, blood pressure, heart rate
Vitamin K1	Warfarin	Skin reaction, anaphylaxis	PT/INR

Two patterns run through the table. Three of the five carry a thrombotic risk — the antifibrinolytics, the factor Xa reversal agent and idarucizumab — because you are re-enabling clotting in a patient anticoagulated for a reason; protamine's signature harms are instead hypotension and anaphylaxis, and vitamin K1's is anaphylaxis with intravenous administration. And the monitoring parameter matches the pathway: PT/INR for warfarin, thrombin-based tests for dabigatran, general coagulation monitoring for heparin.

Memorize the five reversal pairs as units. Heparin–protamine sulfate; warfarin–vitamin K1 with PT/INR; dabigatran–idarucizumab; apixaban and rivaroxaban–factor Xa reversal agent; fibrinolytic state–aminocaproic or tranexamic acid.

Linking receptors to targets

This is the shortest and most testable table in the topic. Each row reads: block this receptor, in this place, and you get this effect — here is a drug that does it.

Receptor	Location	Effect	Example
β₁ (beta-1)	Heart	Decreased heart rate and contractility	Metoprolol
α₁ (alpha-1)	Vessels	Vasodilation	Prazosin
AT₁	Vessels and kidney	Decreased vasoconstriction	Losartan
L-type calcium channel	Heart and vessels	Decreased contractility	Verapamil

Read the effect column carefully: it is what happens when the drug blocks the receptor, not what the receptor does when stimulated. Alpha-1 receptors normally cause vasoconstriction; block them with prazosin and you get vasodilation.

Name the target and you can predict both effects. Therapeutic effect and characteristic adverse effect are usually one action in two places — β₁ blockade lowers blood pressure and causes bradycardia; calcium channel blockade relaxes arterioles and causes ankle edema.

Common adverse drug reactions

Five adverse reactions account for most of what you will be asked:

Adverse reaction	Classes responsible
Bradycardia	Beta blockers, calcium channel blockers
Cough / angioedema	ACE inhibitors
Hyperkalemia	ACE inhibitors, ARBs, potassium-sparing diuretics
Edema	Calcium channel blockers
Orthostatic hypotension	Vasodilators

Running the same idea the other direction, here is the reaction each class is known for:

Class	Signature adverse reaction
Loop diuretics	Hypokalemia, dehydration, hypotension
Thiazide diuretics	Electrolyte imbalance; a problem in sulfa allergy
Potassium-sparing diuretics	Hyperkalemia
Beta blockers	Bradycardia; bronchospasm when nonselective
ACE inhibitors	Dry cough and angioedema, from bradykinin
ARBs	Hyperkalemia and rising creatinine, without the cough
Calcium channel blockers	Peripheral edema; bradycardia and constipation with non-dihydropyridines
Statins	Myopathy and elevated liver function tests
Nitrates and vasodilators	Headache, orthostatic hypotension, reflex tachycardia
Amiodarone	Pulmonary, thyroid, hepatic, neurologic, ocular and skin toxicity
Digoxin	Bradycardia, xanthopsia, nausea and anorexia
Anticoagulants and antiplatelets	Bleeding; thrombocytopenia with heparin

Contraindications and precautions

A contraindication means do not use the drug; a precaution means you may use it but must watch for something specific.

Drug class	Contraindication	Precaution
Beta blockers	Asthma	Diabetes — they mask hypoglycemia
ACE inhibitors and ARBs	Pregnancy	Hyperkalemia
Calcium channel blockers	Heart block	Heart failure, with verapamil
Diuretics	Hypovolemia	Electrolyte imbalance

Several more come from the individual classes: thiazides in sulfa allergy; loop diuretics with caution in severe renal failure; statins in pregnancy and liver disease; nitrates with any phosphodiesterase-5 inhibitor; anticoagulants and antiplatelets in active bleeding or hemorrhagic stroke. ACE inhibitors and ARBs are also contraindicated in bilateral renal artery stenosis, and severe bradycardia is a second contraindication for beta blockers.

Contraindication or precaution? This course states verapamil and heart failure both ways — a contraindication in the calcium channel blocker material above, a precaution in this table — even though the two words are defined as opposites in the sentence before it. Reconcile them this way: verapamil is contraindicated in decompensated heart failure with reduced ejection fraction, because its negative inotropy worsens a failing pump, while a dihydropyridine such as amlodipine is acceptable there. Either wording gives the same exam answer — verapamil is the calcium channel blocker heart failure rules out.

⭐ Pregnancy rules out two whole classes. ACE inhibitors and ARBs are contraindicated in pregnancy, and so are statins — the classes to eliminate first in a pregnant patient.

ADME of cardiovascular drugs

Absorption. Most cardiovascular drugs are given orally, and bioavailability is variable for three reasons: first-pass hepatic metabolism (propranolol, nitroglycerin — nitroglycerin is given sublingually specifically to bypass the first-pass effect for rapid onset); lipid solubility, which determines how readily the drug crosses membranes; and the presence of food, which may increase or decrease absorption.

Distribution. Cardiovascular drugs often have high protein binding (warfarin, verapamil), and volume of distribution affects half-life and tissue effects. Lipophilic agents such as propranolol penetrate the central nervous system and can cause fatigue and depression; hydrophilic agents such as atenolol have limited CNS penetration. The clinically relevant consequence of protein binding is competition: a second drug displaces the first, free drug rises, and toxicity follows — classically warfarin displaced by NSAIDs.

Metabolism. Most are metabolized by hepatic CYP450 enzymes, with CYP3A4 and CYP2D6 the key pathways. The first-pass effect is significant for many oral drugs including beta blockers, calcium channel blockers and nitrates, and some agents are prodrugs requiring hepatic activation — enalapril becomes enalaprilat.

CYP enzyme	Affected drugs	Example interaction
CYP3A4	Verapamil, diltiazem, statins	Grapefruit juice increases levels
CYP2D6	Metoprolol, propranolol	SSRIs increase beta blocker levels
CYP2C9	Warfarin	Amiodarone increases INR

Because these drugs are metabolized in the liver before reaching the systemic circulation, bioavailability falls and higher oral doses are required. Three strategies bypass the first-pass effect: sublingual (nitroglycerin), intravenous (labetalol, furosemide) and transdermal (the clonidine patch).

Excretion. Most cardiovascular drugs are excreted by renal or biliary routes, and renal impairment leads to accumulation. Agents requiring dose adjustment include digoxin, ACE inhibitors such as lisinopril, and some diuretics including thiazides and loop diuretics.

Faculty vs current practice. This course explains warfarin plus an NSAID as protein-binding displacement — free warfarin rises and the patient bleeds — and that is the pharmacokinetic answer to give. Current pharmacology holds that displacement alone rarely produces sustained toxicity, because a higher free fraction is also cleared faster; the real bleeding risk is pharmacodynamic, from platelet COX-1 inhibition plus gastric mucosal injury, with a kinetic contribution from CYP2C9 inhibition by some NSAIDs. Know both; answer displacement.

Know the four ADME letters as one sentence each. A: oral first-pass metabolism is common, and sublingual nitrates bypass it. D: high protein binding, and lipid solubility drives the CNS side effects. M: CYP450-dependent, the site of most drug interactions. E: mainly renal, so dose adjustment is critical in chronic kidney disease.

Pulling it together

Cardiovascular drugs manage chronic conditions by targeting two systems: the autonomic nervous system and the renin–angiotensin–aldosterone system. Understanding classes, mechanisms, clinical uses, adverse reactions and contraindications is what turns a list of drug names into clinical judgment.

The highest-return facts: most antihypertensives work by lowering cardiac output or peripheral resistance; bradykinin explains the ACE inhibitor cough and is why ARBs exist; nonselective beta blockade and asthma do not mix; pregnancy rules out RAAS drugs and statins; the non-dihydropyridine calcium channel blockers are the ones that touch the node; amiodarone injures every organ; nitrates and PDE-5 inhibitors are never given together; and every kinetics question here comes back to first-pass metabolism, protein binding, CYP450 or renal clearance.