Adrenergics Flashcards
clonidine, in some patients
decreases renin and aldosterone concentrations
clonidine effect in different positions
standing: peripheral vasodilation, lying down: decreases heart rate and stroke volume
clonidine given IV
can increase blood pressure
phenylephrine
α1 agonist
dobutamine
β1 (relatively selective) agonist, two sterioisomers; increase in ionotropic (major) and chronotropic effects, autoregulatroy increase in coronary blood flow
isoproternol
non-selective β adrenergic agonist, IV administration results in increase in ionotropic and chronotropic effects, also it causes skeletal, mesenteric, and renal vasodilation (β2) which reflexly reinforces the β1 effects
epinephrine - low dose
low doses: β1 & β2 effects predominate (looks like isoproternol)
epinephrine - high dose
α1, β1 effects predominate, blood pressure increase, increases systolic bp and also diastolic if the dose is high enough
norepinephrine
α1, α2, & β1 agonist; predominant effects are on blood pressure (increases systolic and diastolic), risk of arhythmias, CO stays relatively stable (reflex to vasoconstriction opposes β1 increase in ionotropic and chronotropic effects)
dopamine
norepinephrine metabolic precursor; low doses: activates D1 (Gs) in mesenteric and vascular beds,vasodilation, important in circulatory shock,
dopamine - high doses
β1 adrenergic agonist – stimulates myocardial contraction and rate - increase in CO and systolic BP without change in peripheral vascular resistance. even higher α1
β2 adrenergic agonists
powerful bronchodilators, suppress release of mast cell inflammatory mediators, do not reduce bronchial hyperresponsiveness
selective β2 agonists
albuterol, terbutaline
long acting β2 agonist
salmeterol (12+ hours), treatment of asthma
β2 effects on uterine smooth muscle
relaxation – treatment for premature labor
premature labor treatment
β2 agonist: ritodrine, terbutalin
catecholamine mediated hyperglycemia
α1/β2 effects on hepatic glycogenolysis and increase in lactate concentrations via muscle glycogenolysis, stimulation of lypolysis
insulin secretion
increased by β2,decreased by α2
nasal decongestants
α1 agonist
paroxysmla atrial tachycardia
raise bp with α1 agonist and reflexly slow down the heart
hypotensive states
spinal anesthesia, chronic orthostatic hypotension, shock
types of shock
hypovolemic shock, cardiogenic shock, hyperdynamic shock, anaphylactic shock, septic shock
hypovolemic shock
inadequate venous return (low volume or obstruction)
cardiogenic shock
due to impaired contractile function: MI, heart failute, cardiomyopathy
treatment for cardiogenic shock
relieve ventricular after load with vasodilators, use positive iontropic agents (dobutamine, dopamine)
hyperdynamic shock
fall in peripheral resistance cause by sepsis, anaphylaxis, adrenal insufficiency, or neurological disorders
anaphylactic shock
immediate hypersensitivity response with bronchospasm, mucous membrane edema, cardiovascular collapse
treatment of anaphylactic shock
epinephrine
treatment of septic shock
antibiotics, activated protein C
hyperdynamic shock, high cardiac output
vasopressor
hyperdynamic shock PAWP
low: volume; high: ionotropic agent
clonidine half life
12 hours
dobutamine
sort of selective β1 adrenergic agonist, half life 2 minutes, useful in short term treatment of cardiac decompensation, excessive doses have α1 effect
the ideal aerosolized drug should be
absorbed poorly from the GI tract or extensively metabolized during first pass
salmeterol has a
delayed onset of action
ritodrine
prevention of premature labor, β2 agonist, side effects: reduced peripheral vascular resistance, tachycardia, increased renin secretion, salt and water retention, hyperglycemia, apprehension, anxiety
topical hemostasis
epinephrine
increases renal blood flow, sodium excretion, and glomerular filtration rate
dopamine (short half life, given via IV infusion)
indirectly acting sympathomimetic amines
indirectly cause NE release, less effective on repeated use (tachyphylaxis), slower than endogenous NE in onset and longer in duration, transported via NE uptake system
“mixed acting” sympathomimetic amines
act directly on receptors and indirectly via NE release
purely indirectly acting sympathomimetic amine
tyramine (cheese, etc)
mixed acting, orally effective, sympathomimetic amine
ephedrine
amphetamine
lipid soluble, metabolically blocked, orally active, relatively long acting, prominent CV and CNS effects, used for ADHD and narcolepsy
ephedrine
orally active, CNS stimulant, used for asthma, banned for athletes (α/β agonist, also indirect)
amphetamine CV effects
bp elevation, reflex decrease in heart rate, arrhythmias
amphetamine CNS effects
NE and dopamine release - wakefulness, euphoria, confusion, delirium, panic states, etc. fatal OD: convulsions, coma, cerebral hemorrhage
amphetamine side effects
appetite suppressant
methylphenidate
ritalin: CNS stimulant, used for ADHD, attention at level of cerebral cortex, drug holidays when possible, watch for insomnia and anorexia
paradoxical improvement of ADHD via
dextroamphetamine and methylphenidate
fen-phen
20mil prescriptions in 1996, caused heart valve disease
two centrally acting agents that interfere with adrenergic neuronal function
clonidine and methyl-dopa
methyl-dopa
false neurotransmitter, α2 agonist, accumulates in secretory vesicles, converted to methylNE via same drug that converts dopamine into NE
methyl-dopa is
orally active, decrease peripheral vascular resistance, adverse effects are sedation, dry mouth, hepatic toxicity
what is special about methyl-dopa
false neurotransmitter and a prodrug
reserpine
complex alkaloid from indian snake root plant, binds to and inactivates neuronal storage vesicles (NE, E, dopamine, serotonin)
eventual effect of high dose reserpine
depletion of central and peripheral stores of catecholamines and serotonin
good things about reserpine
lowers blood pressure, is cheap
effects of α adrenergic antagonists are
less obvious when lying down, more obvious in hypovolemic states
compensatory responses to α adrenergic agonists are
tachycardia (fast - more with general α antagonists) and fluid retention (slow)
when α receptors are blocked, epinephrine
vasodilates (β2 vasodilation effects of epinephrine)
α1 antagonists also block
contraction of urinary sphincter, contraction for ejaculation, (causes nasal stuffiness)
effects of α2 adrenergic antagonists
enhanced sympathetic outflow, vasoconstriction, cardiac stimulation
phenoxybenzamine
nonselective α adrenergic blocker, alkylating agent, related to nitrogen mustards, irreversible
preop for pheochromocytoma surgery
phenoxybenzamine
prazoin
selective α1 blocker, 3 hour half life, for primary systemic hypertension
tamulosin
selective α1 blocker, treats benign prostatic hypertrophy (α1A>α1B), 9-15 hour half life
β1 effect
block catecholamine stimulated renin secretion
β blockers are counter-indicated in patients with
asthma, COPD, diabetes (mask tachycardia during hypoglycemic events)
β blockers cause modest
increases in triglycerides and decreases in HDL
selective β1 antagonist
metoprolol (3-4 hrs), atenolol (5-8hrs)
nonselective β antagonists
propranolol (3-5 hrs), carvediolol (7-10 hrs)
propranolol
lipophilic, one a day dosing despite short half life
carevediolol
racemic, antioxidant, CHF treatment
metoprolol
β1, genetic differences in rate of metabolism
atenolol
β1, limited brain penetration
β antagonist and exercise
decreased ability in patients without angina
β antagonist major problem
discontinuation rebound, worsen peripheral vascular disease
β blockers and vasodilators/diuretics
good combinations due to decrease in reflex tachycardia
supraventricular and ventricular arrhythmias
β blockers
early administration after MI
β blocker without intrinsic sympathomimetic activity
β and α1 antagonist
carvediolol (CHF, hypotension?)
in CHF take
carvediolol or metoprolol
acute dissecting aortic aneurysm
β blocker, short term, pending surgery
β blocker also used for
hyperthyroidism, migraine prophylaxis, acute panic syndrome, open angle glaucoma (reduce aqueous humor creation), pheochromocytoma (control catecholamine effects on the heart)
shortest and longest half lives
dobutamine, clonidine
tachyphylaxis
depletion of neurotransmitter from nerve endings