Intro to antihypertensive agents Flashcards Preview

Renal II Exam 2 > Intro to antihypertensive agents > Flashcards

Flashcards in Intro to antihypertensive agents Deck (41):

Hypertension and Cardiovascular Disease

Approximately 29-31% of US adults have hypertension
76.4 million Americans (> 20 years old)
Most common reason for office visits of nonpregnant adults
Only 50.1% of those with hypertension are considered controlled (less than 140/90 mmHg)
Hypertension associated with serious adverse effects:
- Renal failure, coronary disease, heart failure, stroke, dementia


Blood pressure calc and drug strategies

BP – blood pressure
CO – cardiac output
SVR – systemic vascular resistance
Drug Strategies:
Reduce cardiac output and blood pressure is reduced
Reduce systemic vascular resistance and blood pressure is reduced
Compensatory responses may include:
Reflex tachycardia (increased sympathetic activity)
Edema (increased renin activity)


Lifestyle modifications to prevent and manage hypertension

weight reduction
adopt DASH eating plan
Dietary sodium reduction
physical activity
moderation of alcohol consumption


Sites of action of the major classes of antihypertensive drugs

agents that block the production or action of angiotensin
direct vasodilators
sympathoplegic agents (those that alter sympathetic function)


Initial monotherapy options for patients with chronic kidney disease

ACE inhibitr
Angiotensin receptor blocker (ARB)


Initial monotherapy options for patients without CKD

Black- thiazide diuretic, calcium channel blocker

Nonblack- thazide diuretic, ACE inhibitor, ARB, CCB


Diuretics- basics

Increase the rate of urine flow and sodium excretion

Used to adjust the volume and/or composition of body fluids in a variety of clinical situations including (but not limited to):
Edematous states: heart failure, kidney disease and renal failure, liver disease (cirrhosis)
Nonedematous states: hypertension, nephrolithiasis (kidney stones), hypercalcemia, and diabetes insipidus


Diuretics: Molecular Targets

Specific membrane transport proteins
- Sodium/potassium/chloride cotransporter (loop diuretics)
- Sodium/chloride cotransporter (thiazide diuretics)
- Sodium channels (potassium-sparing diuretics)

- Carbonic anhydrase (carbonic anhydrase inhibitors)

Hormone receptors
- Mineralocorticoid receptor (potassium-sparing diuretics)


Carbonic Anhydrase Inhibitors

Prototype: acetazolamide
MOA: inhibits the membrane-bound and cytoplasmic forms of carbonic anhydrase

Results in:
↓ H+ formation inside PCT cell
↓ Na+/H+ antiport
↑ Na+ and HCO3- in lumen
↑ diuresis

Urine pH is increased and body pH is decreased

Other agents: brinzolamide, dorzolamide, methazolamide

Therapeutic Use:
Rarely used as antihypertensives due to low efficacy as single agents and development of metabolic acidosis
Used for glaucoma, acute mountain sickness, and metabolic alkalosis

ADRs: acidosis, hypokalemia, renal stones, paresthesias (with high doses), sulfonamide hypersensitivity


Loop Diuretics

Prototypes: furosemide and ethacrynic acid
MOA: inhibit the luminal Na+/K+/2Cl- cotransporter (NKCC2) in the TAL of the loop of Henle
Results in:
↓ intracellular Na+, K+, Cl- in TAL
↓ back diffusion of K+ and positive potential
↓ reabsorption of Ca2+ and Mg2+
↑ diuresis
Ion transport is virtually nonexistent
Among the most efficacious diuretics available

Diuretic activity tied to secretion rates (act at luminal side of tubule)
t1/2 correlated to kidney function – 0.5-2 hrs (healthy) vs. 9 hrs (end stage renal disease) for furosemide

Therapeutic Use:
Edema, heart failure, hypertension, acute renal failure, anion overdose, hypercalcemic states

ADRs: hypokalemia, alkalosis, hypocalcemia, hypomagnesemia, hyperuricemia, ototoxicity, sulfonamide hypersensitivity (not all)


Thiazide Diuretics

Prototype: hydrochlorothiazide (HCTZ)
MOA: cause inhibition of the Na+/Cl- cotransporter (NCC) and block NaCl reabsorption in the DCT
Results in:
↑ luminal Na+ and Cl- in DCT
↑ diuresis
Enhance the reabsorption of Ca2+ in both DCT and PCT
Largest class of diuretic agents

Therapeutic Use:
Hypertension, mild heart failure, nephrolithiasis (calcium stones), nephrogenic diabetes insipidus

ADRs: hypokalemia, alkalosis, hypercalcemia, hyperuricemia, hyperglycemia, hyperlipidemia, sulfonamide hypersensitivity
More hyponatremic effects than loop diuretics
Use with caution in patients with diabetes mellitus


Potassium-sparing diuretics: Mineralocorticoid Receptor (MR) Antagonists

Spironolactone and eplerenone
Therapeutic Use: hyperaldosteronism, adjunct to K+-wasting diuretics, antiandrogenic uses (female hirsutism), heart failure (reduces mortality)
Do not require access to the tubular lumen to induce diuresis
ADRs: hyperkalemia, acidosis, and antiandrogenic effects


Potassium-sparing diuretics: Na+ channel ENaC Inhibitors

Amiloride and triamterene
Therapeutic Use: adjunct to K+-wasting diuretics and lithium-induced nephrogenic diabetes insipidus (amiloride)
ADRs: hyperkalemia and acidosis


Mineralocorticoid Receptor (MR)

Nuclear hormone receptor responsible for regulating the expression of multiple gene products
Natural agonists include mineralocorticoids – a class of steroid hormones that influence salt and water balance
Examples include aldosterone, deoxycorticosterone, and glucocorticoids (cortisol)
Also known as the aldosterone receptor


Major effects of Ang II

vasoconstriction --> PRESSOR (rapid)

Increase Na+ reabsorption in prox tubule, relase of aldosterone from adrenal cortex, renal vasoconstriction --> PRESSOR (slow)

Vascular and Cardiac Hypertrophy and Remodelling


Pharmaceutical Strategies for Inhibition of the Renin-Angiotensin-Aldosterone System

Aldosterone Receptor (MR) Antagonists

ACE Inhibitors

Angiotensin II Receptor Blockers (ARBs)

Renin Inhibitors



Angiotensin-Converting Enzyme (ACE) Inhibitors

Prototypes: captopril, enalapril, lisinopril

MOA: inhibit the conversion of angiotensin I to the more active angiotensin II; also prevent degradation of bradykinin and other vasodilator peptides

Therapeutic Use:
Hypertension, heart failure, left ventricular dysfunction, prophylaxis of future cardiovascular events (e.g., MI, CAD, stroke) and nephropathy (+/- diabetes)


Benefits of ACE Inhibitors in HTN

Lowers peripheral vascular resistance, and mean, diastolic, and systolic BP
Cardiac function in patients with uncomplicated hypertension is little changed
Stroke volume and cardiac output may increase slightly with sustained treatment
Baroreceptor function and cardiovascular reflexes are not compromised
Responses to postural changes and exercise are little impaired
Evidence that ACE inhibitors are superior in treating HTN in patients with diabetes
Improve endothelial function & reduce CV events more so than CCBs or diuretic and β-blocker combination


ADRs of ACE Inhibitors

* Cough
* Angioedema
* Hyperkalemia – avoid K+-sparing diuretics
* Acute renal failure – particularly in patients with renal artery stenosis
Fetopathic potential (teratogen) – CI in pregnancy

Skin rash
Dysgeusia (altered sense of taste)
Rare: neutropenia, glycosuria, hepatotoxicity
DDIs: antacids, capsaicin, NSAIDs, K+-sparing diuretics, digoxin, lithium, allopurinol


Renal Considerations with ACE Inhibitors

ACE inhibitors prevent/delay the progression of renal disease in type 1 diabetics and in patients with nondiabetic nephropathies (results mixed in type 2 diabetics)
ACE inhibitors vasodilate efferent arterioles > afferent arterioles
Reduces back pressure on the glomerulus and reduces protein excretion
ACE inhibitors usually improve renal blood flow and Na+ excretion rates in CHF

In rare cases, ACE inhibitors can cause a rapid decrease in GFR, leading to acute renal failure (ARF)
Can occur anytime during therapy, even after months or years of uneventful ACE inhibitor treatment


Risk Factors for ACE Inhibitor Induced Acute Renal Failure

MAP insufficient for adequate renal perfusion
Poor cardiac output
Low systemic vascular resistance
Volume depletion (diuretic use)
Renal vascular disease
Bilateral renal artery stenosis
Stenosis of dominant or single kidney
Afferent arteriolar narrowing (HTN, cyclosporin A)
Diffuse atherosclerosis in smaller renal vessels

Vasoconstrictor agents
All cause renal hypoperfusion


Angiotensin II Receptors

G-protein coupled receptors

Two receptor subtypes (AT1 and AT2)

AT1 receptors
Major subtype in adults
Gq → PLC → IP3 + DAG → smooth muscle contraction

AT2 receptors
Activation causes production of nitric oxide and bradykinin
Smooth muscle dilation


Angiotensin II Receptor Blockers (ARBs)

Prototypes: losartan and valsartan
MOA: selectively block AT1 receptors, which leads to:
↓ contraction of vascular smooth muscle
↓ aldosterone secretion
↓ pressor responses
↓ cardiac cellular hypertrophy and hyperplasia
No effect on bradykinin metabolism
Therapeutic Use:
Hypertension, diabetic nephropathy, HF, HF or left ventricular dysfunction after AMI, and prophylaxis of cardiovascular events
ADRs: similar to ACE inhibitors but less cough and edema; CI during pregnancy


ACE Inhibitors VS. ARBs

ARBs reduce activation of AT1 receptors more effectively than do ACE inhibitors

ARBs permit activation of AT2 receptors

ACE inhibitors increase the levels of a number of ACE substrates, including bradykinin

Unknown whether or not these pharmacological differences result in significant differences in therapeutic outcomes


Aliskiren: A Direct Renin Inhibitor

MOA: inhibits renin and blocks the conversion of angiotensinogen to angiotensin I

Does not increase bradykinin

Rise in plasma renin levels but decreased plasma renin activity (ACE inhibitors, ARBs, and diuretics raise plasma renin levels and activity via feedback loop)

Studies show effectiveness comparable to ACEIs and ARBs

ADRs: similar to ACE inhibitors and ARBs; CI in pregnancy


2 types of calcium channel blockers

All CCBs bind to L-type Ca2+ channels. But the two classes bind to different sites, resulting in different effects on vascular versus cardiac tissue.

Prominent cardiac effects, but also act at vascular tissues
Verapamil > Diltiazem

Dihydropyridines (DHPs):
Predominantly arteriolar vasodilation effects
Amlodipine, Clevidipine, Felodipine, Isradipine, Nicardipine, Nifedipine, Nisoldipine


Calcium Channel Blockers: Therapeutic Use

Most useful when combined with another agent to counteract the reflex cardiovascular responses

Hypertensive emergencies
Parenteral formulations

Reduction of O2 demand makes particularly useful


Calcium Channel Blockers: ADRs

Generally very well tolerated
Excessive vasodilation – dizziness, hypotension, headache, flushing, nausea
Diminished by long-acting formulations and long t1/2 agents
Constipation (esp., verapamil), peripheral edema, coughing, wheezing, pulmonary edema

CI: use of verapamil/diltiazem with a b-blocker (potential for AV block)
Verapamil/diltiazem should not be used in patients with ventricular dysfunction, SA or AV nodal conduction defects and systolic BP less than 90 mmHg


Potassium Channel Openers: MOA

Increased potassium permeability stabilizes the smooth muscle cell membrane at resting potential, reducing the probability of contraction


Potassium Channel Openers

-Arteriolar vasodilation
-Diminishing use in hypertensive emergencies due to ADRs:
Excessive hypotension can cause stroke and MI

Arteriolar vasodilation
Therapeutic Use: severe hypertension and baldness (topical)
Headache, sweating, hypertrichosis
Reflex tachycardia & edema – must be used with β-blocker & diuretic to avoid these effects



D1 dopamine receptor agonist
Renal afferent arteries contain dopamine receptors—activation increases blood flow to the kidneys
For hypertensive emergencies & post-operative hypertension
ADRs: tachycardia, headache, and flushing
Should be avoided in patients with glaucoma due to increases in intraocular pressure



MOA: releases nitric oxide from endothelium
- Dilates arterioles, but not veins

Therapeutic Use:
- First-line oral therapy for hypertension in pregnancy, with methyldopa
- Combination with nitrates is effective in patients with heart failure
- Parenteral formulation useful in hypertensive emergencies

- Can induce fluid and sodium retention
- Headache, nausea, anorexia, sweating, flushing, palpitations
- Reflex tachycardia can provoke angina in patients with ischemic heart disease
- Lupus-like syndrome (reversible on drug withdrawal)


Nitroprusside and Organic Nitrates

Prototype organic nitrate: nitroglycerin

- Dilates both arterial and venous vessels—decreases total peripheral resistance and venous return
- Decreases both preload & afterload
- Mainly relaxation of large veins ® ¯ venous return ® ¯ preload ® ¯ O2 demand (major effect), smaller ¯ in afterload

Therapeutic Use: used to treat hypertensive emergencies, heart failure, & angina (nitrates)

- Nitroprusside: excessive hypotension, cyanide poisoning
- Nitrates: orthostatic hypotension, syncope, throbbing headache


β-blocker Use in Hypertension

No longer 1st line treatment for hypertension, except when concomitant with a compelling indication:
- Heart failure
- Recent MI
- Reduced left ventricular function

Predispose to diabetes, particularly when combined with thiazide
Relative CI: asthma
Less stroke protection than other antihypertensives


β-blockers with α-blocking Activity: Labetalol

Selective a1 blocker
Nonselective b1 & b2 blocker
Partial agonist at b2
Therapeutic Use:
IV for severe hypertension
Acceptable option for hypertension during pregnancy


β-blockers with α-blocking Activity: Carvedilol

Nonselective b-blocker + a1-blocker
Also has antioxidant properties


β-blockers with Vasodilating Activity

Non-selective vasodilating β-blockers
- Carteolol, carvedilol, labetalol
β1-selective vasodilating β-blockers
- Betaxolol, nebivolol

These drugs produce peripheral vasodilation through a variety of mechanisms:
↑ NO
Activate β2-receptors
Block of α1-receptors
Block Ca2+ entry
Open K+ channels
Antioxidant activity
Antiproliferative effects



beta 1-selective
Very rapid onset & short duration of action
Used as IV infusion for peri-operative tachycardia and hypertension, hypertensive emergencies, arrhythmias
Used in electroconvulsive therapy


alpha 1-Selective Receptor Blockers

MOA: prevent vasoconstriction of both arteries and veins
↓ total peripheral resistance, ↓ venous return, ↓ preload
Usually do not ↑ heart rate or cardiac output
Do not ↑ NE release (no 2 block)
Favorable effects on lipids (↓ LDL & triglycerides; ↑ HDL)
Relaxes smooth muscle in the prostate

Therapeutic Use: 3rd or 4th line treatment of essential hypertension; added to other agents from different classes in refractory cases; also used in men with concurrent HTN and BPH

ADRs: postural hypotension & syncope, especially with initial doses; usually given at bedtime to minimize hypotensive effects



An a2-adrenergic receptor agonist
IV - increase BP (peripheral a2B) followed by decreased BP (central a2A)
Oral - decreased BP (decreased C.O., preload)
Patch - same as oral
Therapeutic Use:
Essential hypertension (rarely used)
Adjunct for narcotic, alcohol, & tobacco withdrawal (unlabeled)
Dry mouth, sedation, impotence, depression
*** Sudden withdrawal causes hypertensive crisis



False neurotransmitter concept:
- Converted to methyl-NE
- Stored in vesicles instead of NE
- Released & acts as a centrally acting α2-agonist
- Decreases central sympathetic outflow & decreases blood pressure

Therapeutic Use: only used to treat hypertension in pregnancy because of its safety

ADRs (many): sedation, dry mouth, sexual dysfunction, postural hypotension, anemia