Chapter 2 Peripheral nervous system drugs - adrenergic antagonists (peripheral postsynpatic anti-adrenergics) Flashcards
adrenergic antagonists
- block actual receptors (can be competitive)
phenoxy-benzamine (dibenzyline)
- a1, a2
- irreversible alkylation of a receptor (ong-lasting noncompetitive alpha blockade of the postganglionic synapses present in smooth muscles and endocrine glands)
actions:
* a1 - vasodilation
* a2 - blocks sympathetic outflow (brain) and feedback inhibition of NE
* d/t NE presence (activates b? I think) ===> increases insulin release
clinical use
* pheochromocytoma (type of neuroendocrine tumor that grows from cells called chromaffin cells. These cells produce hormones needed for the body and are found in the adrenal glands. The adrenal glands are small organs located in the upper region of the abdomen on top of the kidneys) ===> control hypertensive episodes
undesireable effects
* postural hypotension (blood pooling)
* intense reflex tachycardia and force of contraction (increased d/t blockage of NE feedback control at a2 receptors)
* arrhythmias
* ischemia
* sexual dysfunction
* nasal congestion
pharmcokinetics
* slow onset, but long lasting d/t irreversible binding to receptor
Phentolamine
- a1, a2, competitive
- vasodilation
- used for pheochromocytoma (HTN episodes) // dermal necrosis (skin necrosis)
undesirable effects:
* tachycardia
* cardiac arrhythmias
* prolonged hypotensive episodes
* nasal congestion
* diarrhea
pharmcokinetics
* rapid onset and short half life
prazosin (minipress)
- selective a1, competitive
- vasodilation
- used for HTN
undesirable effects
* no large reflex tachycardia
* postural hypotension (when your blood pressure drops when you go from lying down to sitting up, or from sitting to standing) with first dose
* less sexual dysfunction
doxazosin (cardura)
terazosin
- selective a1, competitive
- vasodilation
- used for HTN, benign prostatic hyperplasia (relaxes smooth muscles produced by blockade of a1 in bladder neck and prostate)
undesirable effects
* postural hypotension with 1st dose
* less sexual dysfunction
* NO large reflex tachycardia
alfuosin (uroxatral)
tamsulosin (flomax)
- selective a1, competitive
- vasodilation
- USED for benign prostatic hyperplasia (a condition in men in which the prostate gland is enlarged and not cancerous or obstruction d/t aging)
undesirable effects
* no reflex tachycardia
* postural hypotension with 1st dose
* less sexual dysfunction
labetalol (trandate) (normodyne)
- a1, b1, b2 // competitive
- decreased BP (a1 blockade) w/o reflex tacycardia (b1 blockade)
- conduction time and refractory period slightly prolonged
uses — HTN, IV for severe HTN
undesirable effects:
1) exacerbate failing heart
2) fatigue
3) impotence
4) diarrhea
5) numbness
6) orthostatic hypotension
pharmacodynamics:
* oral - peak in 1-2 hrs; steady state in 3 days
* iv - extensive 1st pass effect + iv peaks in 5 mins
CONTRAINDICATED —- patients w/ asthma d/t bronchoconstriction
carvedilol (coreg)
- a1, b1, b2 // competitive
- decreased cardiac output, decreased exercise-induced tachycardia, decreased reflex orthostatic tachycardia
- vasodilation + decreased vascular resistance with decreased BP
uses — HTN, CHF
undesirable effects:
1) hepatotoxic
2) postural hypotension
3) hypoglycemia
pharmacodynamics:
* well absorbed
* extensive 1st pass
* terminal elimination half life 7-10 hrs
CONTRAINDICATED — patients w/ astham d/t bronchoconstriction
propranolol (inderal)
- b1, b2, competitive
- dec inotropy (force of heart contraction) and dec chronotropy (heart rate)
- decreased conduction velocity – heart
- Arteries — compensatory vasoconstriction (dwindles over days)
- kidneys — less renin release (b1), l/t increased sodium and h2o retention
- liver decreaased glyconeolysis and slows post-insulin recovery of glucoses
no change in HR or contraction w/ pindolol
- uses — HTN, angina pectoris, SVT, vertricular arrhythmias, MI, migraine prophylaxis, essential tremors and other unlabled uses
undesirable effects:
* further suppress failing heart
* CNS sedation + depression
* rebound HTN
* impotence (erectile dysfunction)
* angina, MI, arrhythmias may occur if abruptly withdrawn
readily enters CNS (significant 1st pass); hepatically metabolized
CONTRAINDICATED — pts w/ asthma d/t bronchoconstriction // b blockers should be weaned rather than abruptly withdrawn
Carteolol (cartrol)
Penbutolol (levatol)
pindolol (visken)
- b1, b2, competitive
- dec inotropy (force of heart contraction) and dec chronotropy (heart rate)
- decreased conduction velocity – heart
- Arteries — compensatory vasoconstriction (dwindles over days)
- kidneys — less renin release (b1), l/t increased sodium and h2o retention
- liver decreaased glyconeolysis and slows post-insulin recovery of glucoses
clinical uses — HTN (both)
undesirable effects
1) bradycarida
2) ventricular arrhythmias
3) dizziness
4) fatigue
5) hyperglycemia
6) hypoglycemia
7) impotence
adjust dose for renal impairment (carteolol)
Contraindicated — bronchospasm (The airways that connect your windpipe to your lungs are called bronchi. Sometimes the muscles that line your bronchi tighten and cause your airways to narrow) and intrinsic sympathomimetic activity (characterizes a group of beta blockers that are able to stimulate beta-adrenergic receptors (agonist effect) and to oppose the stimulating effects of catecholamines (antagonist effect) in a competitive way)
Sotalol (betapace)
- b1, b2, competitive
- dec inotropy (force of heart contraction) and dec chronotropy (heart rate)
- decreased conduction velocity – heart
- Arteries — compensatory vasoconstriction (dwindles over days)
- kidneys — less renin release (b1), l/t increased sodium and h2o retention
- liver decreaased glyconeolysis and slows post-insulin recovery of glucoses
- uses — ventricular arrhythmias, tachycardias
undersirable effects:
1) bradycarida
2) ventricular arrhythmias
3) dizziness
4) fatigue
5) hyperglycemia
6) hypoglycemia
7) impotence
not metabolized – pharmocokinetics
CONTRAINDICATED – Long QT syndrome (Long QT syndrome (LQTS) is a congenital disorder characterized by a prolongation of the QT interval on electrocardiograms (ECGs) and a propensity to ventricular tachyarrhythmias, which may lead to syncope, cardiac arrest, or sudden death)
* contraindicated in asthma or bronchospasm
nadolol (corgard)
- b1, b2, competitive
- dec inotropy (force of heart contraction) and dec chronotropy (heart rate)
- decreased conduction velocity – heart
- Arteries — compensatory vasoconstriction (dwindles over days)
- kidneys — less renin release (b1), l/t increased sodium and h2o retention
- liver decreaased glyconeolysis and slows post-insulin recovery of glucoses
uses – Angina pectoris and HTN
undersirable effects:
1) bradycarida
2) ventricular arrhythmias
3) dizziness
4) fatigue
5) hyperglycemia
6) hypoglycemia
7) impotence
pharmacodynamics — fewer CNS effects than propranolol, longer half life
CONTRAINDICATED – asthma or bronchospasm
timolol (blocadren)
- b1, b2, competitive
- dec inotropy (force of heart contraction) and dec chronotropy (heart rate)
- decreased conduction velocity – heart
- Arteries — compensatory vasoconstriction (dwindles over days)
- kidneys — less renin release (b1), l/t increased sodium and h2o retention
- liver decreaased glyconeolysis and slows post-insulin recovery of glucoses
uses — HTN, MI, migraine propylaxis; used to decrease intraocular pressure (opthalmologic agent)
undersirable effects:
1) bradycarida
2) ventricular arrhythmias
3) dizziness
4) fatigue
5) hyperglycemia
6) hypoglycemia
7) impotence
CONTRAINDICATED – asthma (a respiratory condition marked by spasms in the bronchi of the lungs, causing difficulty in breathing. It usually results from an allergic reaction or other forms of hypersensitivity) or bronchospasm (tightening of the smooth muscles of the bronchi and bronchioles (airways), causing the airways to become narrow and obstructing the movement of air into and out of the lungs)
metoprolol (lopressor)
- b1 specific, competitive
- compared to propranolol — LESS bronchospasm in asthmatics, less inhibition of vasodilation and liver effects
uses — HTN, angina pectoris
undersirable effects —
* lower toxicity than propranolol
* less to likely to inc preipheral resistance, cause bronchospasm or inhibit liver metabolism
pharmacodyamics — readily enters CNS
Atenolol (tenormin)
acebutolol (sectral)
bisoprolol (zebeta)
esomolol (brevibloc)
betaxolol (kertone)
- b1 specific, competitive
- compared to propranolol — LESS bronchospasm in asthmatics, less inhibition of vasodilation and liver effects
uses — HTN
undersirable effects —
* lower toxicity than propranolol
* less to likely to inc preipheral resistance, cause bronchospasm or inhibit liver metabolism
