Exam 3 Flashcards
Adrenergic receptor type and response: SA node
beta 1, increased rate
Adrenergic receptor type and response: AV node
beta 1, Increased conduction
Adrenergic receptor type and response: Ventricles
beta 1, increased contractiity and automaticity
Adrenergic receptor type and response: Blood Vessels (skin and mucosa)
alpha 1, constriction
Adrenergic receptor type and response: Blood vessels, skeletal muscle
beta 2- dilation; alpha 1- constriction
Adrenergic receptor type and response:Blood vessels, abdominal viscera (inc renal)
alpha 1- constriction; beta 2- dilation
Adrenergic receptor type and response: Pulmonary blood vessels
alpha 1- constriction
Adrenergic receptor type and response: Kidney
beta 1- renin release
Adrenergic receptor type and response: GI tract
alpha 1, beta 2: decreased motility and tone, decreased secretion, contraction of sphincters
Adrenergic receptor type and response: Uterus (pregnant)
alpha 1- contraction; beta 2- relaxation
what are alpha 2 receptors?
Adrenergic receptors on the presynaptic neuron terminus that is responsible for feedback inhibition (reduces NE release). They are also present in the CNS, inhibiting NE.
How are catecholamines metabolized after release (2 enzymes)
Monoamine oxidase (MAO) and Catechol-o-methyl-transferase (COMT). All postsynaptic. MAO can also be presynaptic.
Guanethidine: Target/Mechanism
Guanethidine is brought into presynaptic cells via norepinephrine transmitter, where it is packaged into vesicles and basically crowds-out norepinephrine, which is degraded by MAO
Reserpine: Target/Mechanism
Reserpine crosses into presynaptic neurons spontaneously and blocks vesicle membrane transport proteins, preventing concentration of NE into vesicles.
Tyramine and Amphetamine: target/mechanism
Enters presynaptic cell via NE transporter, where it displaces NE from vesicles (crowds-out), causing a short-term massive NE release from cell by NE transporter.
Cocaine, imipramine, atomoxetine: Target/mechanism
Blocks norepinephrine transporter (responsible for norepinephrine reputake. This increases the amount of norepinephrine in the synapse.
Phenylephrine: target/mechanism
it is an agonist of alpha adrenergic receptors (blood vessels constrict peripherally)
phentolamine: target/mechanism
alpha adrenergic receptor antagonist
Norepinephrine: target/mechanism
Agonist for alpha 1 and beta 1 receptors. This increases contractility AND resistance, causing increased blood pressure. HR increases initially, but there will be a vagal reflex reducing within a minute.
Epinephrine: target/mechanism
low doses it is an agonist for beta 1 and beta 2 (CO and HR will increase, but there will also be vasodilation via beta 2, so DBP decreases and SBP climbs). At high doses, it activates alpha 1 receptors which begin to decrease CO. There will be a vagal reflex about a minute later dropping HR. Half life is short so epi will be gone by then.
Dopamine: target/mechanism
At low doses it is selective agonist for dopamine receptor, with some activity on beta 2. This will cause a slight decrease in BP, heart contractility, and HR. At high doses it is an agonist for alpha, beta1 and beta2. First BP will decrease due to beta 2, then an increase due to alpha 1 receptors. Contractility will increase and HR will initially increase, then decrease (vagal reflex).
Dobutamine: target/mechanism
At low doses it is an agonist for beta1 receptors, selectively affecting contractility without affecting RATE. At higher doses it affects alpha 1 and beta 1, as well as some activity against beta2 and alpha receptors.
Isoproterenol: targtet/mechanism
Agonist for beta receptors (1 and 2).
Beta 1 receptors: which catacholamines does it have highest affinity for?
Iso>epi=NE
Beta 2 receptors: which catacholamines does it have highest affinity for?
iso>epi»NE
Alpha 1 receptors: which catacholamines does it have highest affinity for?
epi>NE»iso
In general, what do beta 1 receptors do when activated?
Increase heart contractility and rate increasing CO and BP with a stimulatory g-protein linked pathway (in heart). In kidney: release renin
In general, what do beta 2 receptors do when activated?
Vasodilation to decrease total peripheral resistance. Bronchodilation.
In general, what do alpha 1 receptors do when activated?
They cause vasoconstriction to increase peripheral resistance and increase blood pressure.
In general, what do alpha 2 receptors do when activated?
Alpha 2 are autoreceptors for NE on pre and postsynaptic neurons in the brain. They BLOCK sympathetic outflow in CNS. In post-ganglionic neurons they are found only on presynaptic neurons and INHIBIT NE release.
Epinephrine: indication
Anaphylactic shock: Beta 2 stimulation opens airways, supresses histamine and renin release. Incidental increase in blood pressure via alpha 1.
Asthma/hypersensitivity (same)
Topical hemostasis: Shrinks mucosa via alpha 1
Cardiac arrest: resusitate heart via Beta 1
Epinephrine: toxicity
Arrhythmia, cerebral vascular accident. Less serious: anxiety, fear, palpitations, HA, tremors.
Norepinephrine: indication
Remember: beta1 and alpha1 only (no effect on beta 2s). Typically used in shock (neurogenic). Increases heart rate and contractility, increases blood pressure, no change in cardiac output due to vasoconstriction (alpha 1). Decreases glycogen synthesis via alpha 1.
Norepinephrine: toxicities
Similar to Epinephrine
Isoproterenol: indication
Agonist of beta 1 and 2. Increases heart rate but decreases blood pressure via vasodilation. Relaxes bronchi. It is used in emergencies to stimulate heart in patients with heart block or to prepare for insertion of pacemaker.
Isoproterenol: toxicity
Arrhythmia, tachycardia, palpitations, angina.
Dopamine: indication
at high enough doses to stimulate alpha and beta receptors: Increases heart rate, decreases blood pressure (via DA, unless at higher doses and activates alpha 1). Used in cardiogenic shock (drug of choice)
Dopamine: toxicities
Due to excessive sympathetic stimulation (tachycardia, angina, arrhythmias) and DA receptor stimulation of chemotrigger zone (causes nausea and vomiting). Does not cross BBB)
Dobutamine: indication
In certain types of heart failure (open heart surgery) and acute infarct. Selective for B1 receptors and basically increases contractility without affecting rate.
Dobutamine:
Arrythmias. Does not cross BBB, so no CNS effects.
Alpha 1 agonists: indication
Decongestion of mucous membranes, raises blood pressure, dilates pupils
Alpha 1 agonists: toxicities
Elevate blood pressure
Phenylephrine: indication
decongestant, pupilary dilator
Ephedrine: indication
(weak alpha and beta agonist). Used as a nasal decongestant and a pressor (increases blood vessel constriction)
Non-catecholamine alpha agonists: drug list
Phenylephrine, Ephedrine, Amphetamine
Catecholamines: drug list
Epinephrine, Norepinephrine, isoproterenol, dopamine, dobutamine.
Catecholamines: ADME
Route: IV, IM, topical, inhaled. Epinephrine and NE cross into CNS, dopamine, dobutamine, and isoproterenol do not. All are rapidly metabolized by catecholamine-o-methyl transferase (COMT) and methyl-amine transferase (MAO) EVERYWHERE including in the blood. Very short half-life ~2 mins
Beta 2 stimulators: indication
Bronchial asthma, anaphylaxis, relaxation of pregnant uterus (delays labor)
beta2-stimulators: toxicity
related to incidental beta 1 activation.
Beta 2 stimulators: drug list
ephedrine, terbutaline, albuterol
CNS stimulants: drug list
Amphetamine, methylphenidate, atomoxetine (mech only)
Amphetamine: indication
Narcolepsy, weight reduction
Methylphenidate: indication
ADHD
CNS stimulants: toxicities
Excessive cardiovascular effects.
Xanthines: drug list
caffeine, theophylline
Xanthines: target/mechanism
Inhibits phosphodiesterase (which breaks-down cAMP), which is the second messenger for beta receptors. This causes a similar effect to beta agonists. Also antagonists of adenosine receptors (sleepiness). This is responsible for CNS stimulation. It will cause a decrease in BP (due to decreased vascular resistance from Beta2 receptors) an INCREASE in contractility (beta1 receptor) and an increase in HR.
Xanthines: indication
bronchial asthma, acute and chronic.
Selective alpha blockers: target/mechanism
Reversibly block alpha 1 receptors only (which are generally responsible for vasoconstriction). . In general this will decrease BP, and cause reflex tachycardia.
If a drug affects alpha and beta receptors equally, which effect will predominate?
Alpha1s are distributed much more widely than beta2s, so alpha (constriction) effects will predominate.
Alpha blockers (irreversible): target/mechanism
block alpha 1 receptors (somewhat selective over alpha 2) irreversibly. Drug action continues until new alpha 1s can by synthesized (24 hrs)
Selective alpha blockers: drug list
prazosin
Alpha blockers (irreversible): drug list
phenoxybenzamine. phentolamine
Non-selective alpha blockers: mechanism
Block alpha 1 AND alpha 2 receptors (will prevent feedback inhibition of NE release). Will decrease BP but increase NE onto Beta 1 receptors, causing a greater tachycardia than you would see with a selective alpha blocker.
Prazosin: indication
Hypertension
Phenoxybenzmine: indication
pheochromaocytoma (adrenal tumor) or BPH (to relax smooth muscle in bladder)
Non-selective beta blockers: drug list
propranolol, timolol
Alpha-blockers: toxicity
postural hypotension, reflex tachycardia (WORSE with non-selective), nasal congestion, inhibition of ejaculation.
Epi reversal?
effects of epinephrine in the presence of an alpha blocker. Normally you get a drop in BP due to action on beta2, then an increase in BP (pressor) with increasing concentration due to alpha 1 receptor response. With alpha 1s blocked, effect of epi is only a depressor effect (beta 1).
Non-selective beta blocker: target/effect
Decreases HR due to B1 block, decreased CO, decreases conduction velocity (HR) and decrease oxygen demand. There is also a decrease in plasma RENIN (causing vasodilation). Finally, there is a decrease in sympathetic tone due to effects in the CNS. There is a “direct” effect of beta2 receptors that increases resistance, but it is slight.
Beta-blockers: contraindication
Asthmatics (bronchospasm)
Timolol: indication
treatment of glaucoma via action on beta 1 receptors.
Selective beta-blockers: drug list
Atenolol
Selective beta blocker: target/effect
Cardiac effects are similar to non-selective, but there is less danger of respiratory side effects. At high doses, it is no longer “selective”
Beta-blockers: indication
Hypertension (usually with diuretics and vasodilators), cardiac arrhythmias, angina, prophylaxis of migraine (low dose), may inhibit cancer progression, early MI or after, Pheochromocytoma, glaucoma, heart failure, performance anxiety.
Beta-blockers: toxicity
decrease CO, heart block, bradycardia (all due to beta 1 block); bronchoconstriction (due to beta 2 block), CNS depression/lethargy
Alpha 2 agonists: target/mechanism
Bind pre and post synaptically to norepinephrine alpha 2 receptors in the brain, reducing sympathetic outflow and increases feedback inhibition of norepinephrine.
Alpha 2 agonists: drug list
Clonidine (directly against alpha 2); and alpha-methyl-dopa (prodrug).
Alpha 2 agonists: indication
Essential hypertension (alpha-methyl-dopa is safe in pregnancy), opioid withdrawal (clonadine), open angle glaucoma, ADHD,
Alpha 2 agonists: toxicity
Dry mouth, sedation. Clonidine can cause hypertensive crisis if withdrawn abruptoly, alpha-methyl-dopa can cause a positive Coombes test (autoimmune).
Isoproterenol: target
Selective for beta 1 and beta 2 receptors.
How does heart failure look on a Frank-Starling curve? What about stroke volume and ejection fraction?
The curve is very flat. Compensatory sympathetic tone does not yield increased cardiac output. Renin-angiotensin system activates (due to sympathetic tone) and volume increases along with arteriole constriction. Initially End diastolic volume, end diastolic pressure, end systolic volume, and end systolic pressure all increase. The result is the same stroke volume with a drastically decreased ejection fraction.
Describe the general treatment approach to CHF (3 parts)
Decrease preload (diuretics, ACE inhibitors, AR antagonists, Aldosterone antagonists); Decrease OR stabilize contractility (decrease in mild, stabilize if afib); DECREASE afterload (Combined vasodilators, AR antagonists). Polytherapy is the norm.
Spironalactone: effect in CHF
Reduces renal Na absorption by blocking aldosterone RECEPTOR. Optimal effect at low concentrations when diuretic effect is minimal. Protects heart from fibrosis caused by excessive aldosterone.
Mortalitiy benefit in CHF when used along with ACE inhibitor, beta-blocker, diuretics)
Esmolol: useful for
emergency procedures due to its 8 min half life.