Cardiovascular agents lecture III Flashcards
Nitric oxide is
endogenous, lipophilic, highly reactive, and a free radical
Elimination half time of nitric oxide is
a few seconds; it does not stay around for long!
Nitric oxide is eliminated via
oxidized to form NO
terminates its action
Endothelin derived relaxing factor is
also known as nitric oxide and it increases CAMP
Nitric oxide is formed from
arginine by NOS
nNOS is found in
the neuronal tissue
iNOS is found in
macrophages
eNOS is found in
endothelium & is what we’re most concerned with
Nitric oxide can be (biological roles)
protective or pathogenic
our focus is on the vasodilator role
Mechanism of action of nitric oxide:
nitric oxide forms from arginine and that goes into smooth muscle cell and stimulates guanylyl cyclase
that forms cyclic GMP which results in relaxation
Nitrovasodilator (NO donor) drugs include
organic nitrates- nitroglycerin, isosorbide dinitrate, isosorbide mononitrate
Sodium nitroprusside
amyl nitrite
nitric oxide gas-used in neonates or pulmonary hypertension
The mechanism of action of organic nitrates is similar to nitroprusside but
-it requires metabolism to release NO; depends on the availability of the other components needed for metabolism
The mechanism of action of sodium nitroprusside
NO release resulting in activation of GC in vascular smooth muscle, formation of cGMP, vascular smooth muscle relaxation and vasodilation
The tolerance effect is typically seen in
organic nitrates because it needs the metabolism step to release nitric oxide and if you run out of enzymes to metabolize the drug is unable to work
Sodium nitroprusside works by
spontaneous breakdown to NO & cyanide causing relaxation of arterial and venous smooth muscle
Sodium nitroprusside is metabolized via
cyanide combines with sulfur groups to form thiocyanate; then undergoes renal excretion
What is the half-life of sodium nitroprusside versus thiocyanate?
sodium nitroprusside- 2 minutes
half-life thiocyanate- 2-7 days (increased with impaired renal function)
The onset of action and duration of sodium nitroprusside is
onset <2 minutes
duration 1-10 minutes
The renal effects of sodium nitroprusside includes
vasodilation without significant changes in GFR
The CNS effects of sodium nitroprusside include
increased cerebral blood flow and ICP
The blood effects of sodium nitroprusside include
inhibits platelet aggregation
The cardiovascular effects of sodium nitroprusside include
decreased arterial/venous pressure, decreased peripheral vascular resistance, decreased afterload (in HF or MI- CO may increase due to decreased afterload), slight increase in HR
LACKS significant effects on nonvascular smooth muscle and cardiac muscle
Sodium nitroprusside is used for:
hypertensive crisis= BP reduction to prevent/limit target organ damage
controlled hypotension during surgery- to reduce bleeding when indicated
CHF-acute, decompensated
Acute MI- to improve CO in LV failure and low CO post MI
Sodium nitroprusside has limited use in acute MI due to
coronary steal- altered blood flow results in diversion of blood away from ischemic areas
Sodium nitroprusside has limited clinical uses because
it is short acting and very unstable
Adverse effects of sodium nitroprusside include
profound hypotension, cyanide toxicity, methemoglobinemia, thiocyanate accumulation, increased serum creatinine (transient), increased ICP, HA, nausea, restlessness, flushing, dizziness, palpitation
Cyanide toxicity and sodium nitroprusside
often dose/duration related but can occur at recommended doses, tissue anoxia, lactic acidosis, confusion, death, venous hyperoxemia- tissues cannot extract oxygen
Sodium nitroprusside and methemoglobinemia
iron in hemoglobin is oxidized to iron with impaired oxygen affinity, reduced O2 delivery to tissues (hypoxia); metHb >10% symptomatic
Methemoglobinemia should be considered as differential diagnosis in patients with
impaired oxygenation despite adequate cardiac output and arterial oxygenation
The reversal agent of methemoglobinemia is
methylene blue
Thiocyanate accumulation can cause
hypothyroidism due to impaired iodine uptake
neurotoxicity, including tinnitus, miosis, and hyperreflexia
increased risk w/ prolonged infusion & renal impairment
Sodium nitroprusside interacts with
hypotensive drugs including negative inotropes, general anesthetics and circulatory depressants
phosphodiesterase type 5 inhibitors (i.e. sildenafil)
soluble guanylate cyclase stimulators
will see a large drop in BP with these drugs
Sodium nitroprusside stability
unstable
sensitive to light and temperature
needs to be wrapped with opaque material
results in discoloration of fluid
When administering sodium nitroprusside,
must be shortest infusion duration possible to avoid toxicity, if reduction in BP not obtained within 10 minutes @ max infusion rate then it needs to be discontinued
The mechanism of action of nitroglycerin includes
NO release through cellular metabolism- glutathione- dependent pathway
requires thiols
when NO is released it stimulates guanylyl cyclase and formation of cGMP causing vascular smooth muscle relaxation and peripheral vasodilation
The primary action of nitroglycerin is at
venous capacitance vessels
Sites of action of nitroglycerin include
primary at venous capacitance vessels
mildly dilates arteriolar resistance vessels
dilation of large coronary arteries
Nitroglycerin’s action at the myocardial arteries causes
increased myocardial O2 supply
Nitroglycerin’s action at the arteriolar resistance vessels causes
modest decrease in afterload and decreased myocardial O2 demand
Nitroglycerin’s action at the venous capacitance vessels causes
decreased preload
decreased myocardial O2 demand
Nitroglycerin’s effect on the CV system includes
decreased venous return; decrease L & R ventricular end diastolic pressure, decreased CO, no change in SVR, increased coronary blood flow
Nitroglycerin’s pulmonary effects include
bronchial dilation and inhibition of hypoxic pulmonary vasoconstriction
Tolerance to nitroglycerin results
after 8-10 hours and diminishes effectiveness
Nitroglycerin should be used with caution in
volume depletion, hypotension, bradycardia or tachycardia, constrictive pericarditis, aortic/mitral stenosis, inferior wall MI and right ventricular involvement
Effects of nitroglycerin on blood
inhibits platelet aggregation
Clinical uses of nitroglycerin include
angina, hypertension (perioperative HTN, hypertensive emergencies, postop hypertension), controlled hypotension during surgery, NSTEMI, acute MI (limits damage), HF-low output syndromes
Nitroglycerin is used in HF and low output syndromes because
it decreases preload and relieves pulmonary edema
Nitroglycerin is used in angina because
it reduces myocardial oxygen requirements
venodilation decreases venous return to the heart which reduced RVEDP and LVEDP
Adverse CNS effects of nitroglycerin include
throbbing HA & increased ICP
Adverse CV effects of nitroglycerin include
orthostatic hypotension, dizziness, syncope, flushing, reflex tachycardia (baroreceptor), vasodilation, venous pooling, decreased CO
Hematologic adverse effects of nitroglycerin include
methemoglobinemia (rare)
Nitroglycerin is not given orally because
it has a large first-pass effect of 90%
Nitroglycerin is metabolized via the
liver-denitrated by glutathione-organic nitrate reductase to glyceryl dinitrate and then mononitrate
Nitroglycerin has drug interactions with
antihypertensive drugs-additive effects
selective PDE-5 inhibitor drugs (avanafil, sildenafil)
Guanylate cyclase stimulating drugs
anything that is working to increase cGMP will have potentiation
Nitroglycerin and selective PDE-5 inhibitor drugs
absolute contraindication
profound potentiation
possible life-threatening hypotension and/or hemodynamic compromise
accumulation of cGMP by inhibiting its breakdown
Isosorbide mononitrate and dinitrate are used for
prevention of angina
used for HF in black patients in combination with hydralazine
can be given PO
Isosorbide mononitrate and dinitrate should not be given to patients using
PDE5 inhibitor drugs
Phosphodiesterase enzymes are
a family of enzymes that breakdown cyclic nucleotides
regulate intracellular levels of 2nd messengers cAMP & cGMP
Phosphodiesterase enzyme inhibitors work by
boosting levels of cyclic nucleotides by preventing breakdown
Non-selective drugs that inhibit PDE include
caffeine and theophylline
The mechanism of action of PDE5 inhibitors is
cyclic GMP is boosted resulting in vasodilation
PDE5 acts on
vascular smooth muscles to relax (specifically erectile tissue & the lung)
PDE5 is used clinically for
erectile dysfunction & pulmonary hypertension
PDE5 drugs include
sildenafil, tadalafil, vardenafil
PDE5 is selective for
cGMP
PDE4 is selective for
cAMP
PDE4 functions via the
immune & inflammatory systems
PDE4 is used clinically for
COPD to decrease inflammation and decrease remodeling
PDE4 drugs include
roflumilast
PDE3 drugs include
amrinone, milrinone, and cilastazol
PDE3 drugs are used clinically as
positive inotropes, peripheral vasodilator, limited for acute HF
intermittent claudication-cilastozol
PDE3 drugs are selective for
cAMP & cGMP
PDE3 drugs function at
cardiac contractility and platelet aggregation
The mechanism of action of milrinone is
inhibits breakdown of cAMP
Milrinone is clinically used for
acute HF or severe chronic HF
cardiogenic shock
heart transplant bridge or postop
Milrinone causes effects at
inotropy–> increased cardiac contractility
vasodilation
little chronotropic activity
Adverse effects of milrinone include
arrhythmias & hypotension
The onset, half-life and metabolism of milrinone
onset: 5-15 minutes (IV)
half-life: 3-6 hours
majority not metabolized; >80% excreted renally unchanged
Describe the renin angiotensin system
renin converts angiotensinogen to angiotensin I
converting enzyme turns angiotensin I to angiotensin II
Angiotensin II stimulates aldosterone secretion which increases water and sodium retention and increases preload
Angiotensin II also causes constriction of vascular smooth muscle which increases afterload
Renin is secreted by
the JG apparatus
Renin causes
vasoconstriction and sodium retention
The RAAS is synergistic with
the SNS by increasing the resistance of noradrenaline from the sympathetic nerve terminals
Renin release is stimulated by
decreased blood pressure, Na+, beta 1 receptor activation
Angiotensin converting enzyme is located
in the membrane of endothelial cells
forms Ang II from Ang I
metabolism of bradykinin to inactive form
Aldosterone causes
increased sodium reabsorption, water retention, and secretes K+
Angiotensin II causes
potent vasoconstriction via the AT1 receptor
aldosterone secretion at the AT1 receptor
What drug can block the increased heart rate and release of renin?
metoprolol because it blocks the beta 1 in the heart and beta 2 in the kidneys
Blocking aldosterone causes
hyperkalemia
Angiotensin II works on the
AT1 receptor
ACE inhibitors work at
AT1 receptors
mediates hypertrophy which is why it is used in HF
The RAAS system can be blocked via
ACEI, Renin inhibitors, ARBs, beta blockers, and aldosterone inhibitors
ACEI cause a decrease in
angiotensin II and an increase in bradykinin
ACEI increase bradykinin which causes
vasodilation, cough, and angioedema
ACEI decreases angiotensin II which causes
vasodilation, decreased remodeling, decreased sympathetic output, increase natiuresis, and decreased aldosterone (decreased Na+/H2O retention, increased K+ retenetion)
ACEI drugs have the suffix of
“pril”
Bradykinin causes
NO & prostacyclin formation leading to vasodilation (heart, kidney, microvascular beds)
inflammatory actions–> increased capillary permeability
ACE-I drugs MOA
block the conversion of AngI to Ang II
prevent vasoconstriction
prevent aldosterone secretion, decreasing Na & water retention
ACE-I drugs treat
HTN, CHF, post MI, diabetic neuropathy, & mitral regurgitation (first line therapy)
more effective in DM pts
delay progression of renal disease
Clinical effects of ACE-I include
decreased BP, peripheral vascular resistance
decreased preload, afterload
decreased cardiac workload
does not result in reflex tachycardia
improves/prevents LV hypertrophy, remodeling
improves morbidity/mortality HF
diabetic neuropathy delays progression (improves renal hemodynamics)
ACE-I has drug interactions with
K+ sparing diuretics and K+ supplements
ACE-I drugs tend to be
pro-drugs meaning they are inactive until metabolism step forms active metabolism
Contraindications for ACE-I include
renal artery stenosis as they may develop renal failure due to efferent arteriole constriction
contraindicated in pregnancy
ACE-I adverse effects include
hypotensive symptoms, syncope, “1st dose effect” possible
hyperkalemia
decreased GFR, increased BUN & serum creat., renal dysfunction
dry cough (5-20%) bradykinin related
angioedema-bradykinin related
fetal malformations- teratogenic
ARBs suffix
‘sartan’
Captopril side effects:
Cough Angioedema/ agranulocytosis Proteinuira/potassium excess taste change orthostatic hypotension pregnancy (contraindication) renal artery stenosis (contraindication) increases renin liver toxicity/ leukopenia
ARBs have interactions with
K+ sparing diuretics ad K+ supplements
ARBs are contraindicated in
renal artery stenosis and pregnancy
Adverse effects of ARBs include
similar to ACEI
less frequent cough & angioedema
Clinical effects and uses of ARBs are
similar to ACEi
ARBs mechanism of action
competitive antagonist @ AT1 receptor
blocks effects of ang II mediated by At1 receptor
does not block breakdown of BKN- thus BKN does not accumulate
Differences between ACEi and ARBs
no difference between efficacy in HTN
ARBs slight more tolerable, less likely to be discontinued
ACEi have been around longer so higher quality of data
Aldosterone antagonist includes
spironolactone, eplerenone
Mechanism of action of aldosterone antagonist
competitive antagonist at mineralocorticoid receptor (kidney but also heart, blood vessels, and brain)
prevent nuclear translocation of receptor
blocks transcription of genes coding for Na+ channels
Effects of aldosterone antagonists include
increased sodium, H2O excretion, mild diuresis
Increased K+ reabsorption
Uses of aldosterone antagonist include
HTN, HF, K+ sparing diuresis, hyperaldosteronism,
spironolactone- off label- acne, PCOS, hirsutism
Adverse effects of aldosterone antagonists include
hyperkalemia
spironolactone– broad; includes hepatic, renal, serious derm, GI, menstrual irregularities
Drug interactions with aldosterone antagonists include
other K+ sparing (ACEI, ARBs, etc.)
K+ supplements
NSAIDs (increased renal risks)
The mechanism of action of hydralazine
release of NO from endothelial cells
inhibition of Ca release from SR
The effects of hydralazine include
vasodilates arterioles, minimal venous effect, decreased SVR, DBP reduced» SBP, increases HR, SV & CO
Clinical uses of hydralazine include
hypertension-usually in combo w/ beta blocker & diuretic (to limit SNS effects)
HF= reduced EF
Adverse effects of hydralazine include
HA, nausea, palpitations, sweating, flushing, reflex tachycardia, tolerance/tachyphylaxis, sodium and H2O retention, angina with EKG changes, lupus (reversible)
Hydralazine is contraindicated in
CAD, mitral valve, RH disease
The mechanism of action of minoxidil is
directly relaxes the arteriolar smooth muscle little effect on venous capacitance
increases the efflux of K+ from VSM resulting in hyperpolarization and vasodilation
Effects of minoxidil include
dilates arterioles, not veins
use in hypertension (limited to later-line therapy due to risk-benefit profile)
Clinical uses of minoxidil include
hypertension-later line therapy
usually in combination with beta blocker & diuretic (to limit SNS effects)
Adverse effects of minoxidil include
tachycardia, increased myocardial workload palpitations, angina sodium/fluid retention, edema weight gain hypertrichosis
Warnings with minoxidil include
fluid retention, pericardial effusion/tamponade, rapid BP response, sinus tachycardia, elderly