Adrenergics Flashcards
Direct acting adrenergic agonists:endogenous catecholamines (and D1 agonist) Drugs
Epinephrine
Norepinephrine
Dopamine
Fenoldopam
Epinephrine receptors
Alpha and beta2
Low dose: beta effects (vasodilation)
High dose: alpha effects (vasoconstriction)
Epinephrine effect
High dose-> potent vasopressor : increases BP (systolic > diastolic) -> +ve chronotropic and inotropic effects (beta 1) and vasoconstriction (alpha 1) -> increases CO (and O2 demand from heart)
Bronchodilation (beta 2)
Relaxed GI smooth muscle with contracted sphincters
Relaxed detrusor (beta 2) and contracted sphincter (alpha 1)
Prostatic smooth mm. contraction
Metabolic: hyperglycemia due to increased glycogenolysis and glucagon release (beta 2); net inhibition of insulin secretion (alpha 2 inhibits while beta 2 enhances secretion)
Increased lipolysis through beta 3 activation (increased cAMP and HSL)
DOC for pts in anaphylactic shock; cardiac arrest, asthma attacks combined with local anesthetics to increase duration; glaucoma (decreased production of aqueous humor)
Epinephrine PK
Rapid onset
Brief duration
Administered through IV in emergencies
Other routes include SC, ET tube, inhalation, topically in the eye
Do not give orally due to inactivation by intestinal enzymes
Epinephrine Adverse
CNS disturbances: Restlessness, fear, apprehension, headache, tremor (may be secondary to effects outside of CNS)
ICH due to increased BP
Cardiac arrhythmias-especially in patients on digitalis
Pulmonary edema
Epinephrine “other”
Synthesized from tyrosine in the adrenal medulla
Polar molecule: does not enter CNS in therapeutic doses
Metabolized by COMT and MAO -> VMA and metanephrine
Hyperthyroid may enhance CV actions likely due to upregulation of receptors
Cocaine prevents reuptake
Beta blockers cause predominate alpha effects such as increased TPR and BP
Norepinephrine receptor
alpha and beta 1 >beta 2
Norepinephrine effect
Vasoconstriction (alpha 1) -> increased PVR -> increased SBP/DBP and MAP Bradycardia due to decreased sympathetic outflow following the baroreceptor response (indirect effect through M2) Induces hyperglycemia (less potent than epi) Limited therapy value: *can treat shock*, but dopamine is better due to preservation of renal blood flow
Norepinephrine adverse
NE may cause kidney shutdown
Norepinephrine Other
Baroreceptor reflex coutneracts local action which can be blocked by pretreatment with atropine -> reveals direct effect of tachycardia
Dopamine receptor
D, alpha, beta
Dopamine effect
Central regulator of movement
CVS: low doses vasodilate (D1 receptors, cAMP) especially at renal, mesenteric and coronary
DOC for cardiogenic and hypovolemic shock : increase GFR, renal blood flow and sodium excretion -> preservation of renal function
Inotropic effect at intermediate concentration (beta 1) and increasing release of NE
Increase in systolic BP
High concentration -> alpha 1 mediated vasoconstriction
Dopamine PK
Ineffective orally (metabolism by MAO and COMT)
Dopamine adverse
Overdose-> sympathomimetic symptoms
Can cause nausea, HTN, arrhythmia but is short lived due to rapid metabolism to HVA
Dopamine other
Dopamine does not cross BBB
Fenoldopam receptor
D1
Fenoldopam effect
Peripheral vasodilation -> used in short term management of inpatient HTN
Fenoldopam PK
give continuously via IV, not bolus
Direct acting adrenergic beta agonists
Isoproterenol Dobutamine Terbutaline Alburterol Salmeterol Formoterol
Isoproterenol receptor
Beta 1 and 2
Isoproterenol effect
CVS: increase CO through rate and force of contraction (AV block or C arrest)
Major Decrease in TPR through vasodilation (beta 2) because there is no alpha 1 opposing it
Slight increase in SBP, decrease in MAP and DBP, tachycardia
Bronchodilation and GI smooth muscle relaxation mediated by beta 2
Use stimulate heart in emergency
Isoproterenol PK
most reliable when given parenterally or inhaled
Isoproterenol adverse
similar adverse effects compared to epi:
CNS disturbances: Restlessness, fear, apprehension, headache, tremor (may be secondary to effects outside of CNS)
ICH due to increased BP
Cardiac arrhythmias-especially in patients on digitalis
Pulmonary edema
Dobutamine receptor
beta 1
Dobutamine effect
Acute management of congestive heart failure: increases contractility
Increases CO with little change in heart rate -> O2 demands of the myocardium are not significantly affected gives it an advantage over other sympathomimetics
Dobutamine PK
can build up tolerance with long term use
Dobutamine other
Racemic mixture: -ve alpha one and beat beta one agonist; +ve alpha 1 antagonist and potent beta 1 agonist
Net effect: selective Beta 1
Terbutaline receptor
Beta 2
Terbutaline effect
Bronchodilator
Emergency treatment of status asthmaticus
Reduces uterine contraction in premature labor
Terbutaline PK
Resorcinol ring -> not metabolized by COMT giving it a longer duration
Oral, Inhalation or SC
Terbutaline other
Selectivity is lost at high concentrations
Used in treatment of asthma without having effects on heart
Albuterol other
Selectivity is lost at high concentrations
Used in treatment of asthma without having effects on heart
Salmeterol and Formoterol other
Selectivity is lost at high concentrations
Used in treatment of asthma without having effects on heart
Albuterol Receptor
Beta 2
Salmeterol and Formoterol receptor
Beta 2
Albuterol effect
Inhalant bronchodilator; relief of symptoms in asthma
Salmeterol and Formoterol effect
Bronchodilator
Long acting-> not used for prompt relief of bronchospasm
Salmeterol and Formoterol PK
Slow onset, but prolonged action (12 hrs) after inhalation
Direct acting alpha agonist drugs
Phenylephrine
Clonidine
Methyldopa
Brimonidine
Phenylephrine receptor
alpha 1
Phenylephrine mechanism
Peripheral vasoconstriction
Phenylephrine effects
Vasoconstrictor: increase SBP and DBP
Nasal decongestant
Mydriasis
Tx of supraventricular tachycardia
Phenylephrine Other
NO direct effect on heart, but does cause reflex bradycardia after parenteral administration
Clonidine receptor
Alpha 2
Clonidine Mechanism
Partial agonist** : activation of central alpha 2 receptors suppresses sympathetic outflow
Clonidine effect
Antihypertensive
Clonidine PK
Acute rise in BP due to transient vasoconstriction when given IV, but not orally
Clonidine adverse
Centrally acting antiadrenergic drugs: sedation, mental lassitude, impaired concentration
Methyldopa adverse
Centrally acting antiadrenergic drugs: sedation, mental lassitude, impaired concentration
Methyldopa receptor
alpha 2
Methyldopa mechanism
Central acting anti HTN
Methyldopa effect
Metabolized to alpharmethylnorepinephrine which causes effects similar to clonidine: decrease TPR and BP
DOC in pregnant patients with HTN
Methyldopa adverse
Can cause +ve Coombs test or hemolytic anemia or hepatitis
Brimonidine receptor
alpha 2
Brimonidine mechanism
Decrease aqueous humor production along with increased outflow
Brimonidine effect
Decrease intraocular pressure in glaucoma
Indirect acting Adrenergic agonist drugs
Amphetamine
Methylphenidate
Tyramine
Amphetamine mechanism
Displaces catecholamines from storage vesicle
Weak inhibitor of MAO
Blocks catecholamine reuptake
Amphetamine Effect
Increase BP through alpha 1 and Beta effects
Central stimulatory action: alertness, decrease fatigue and appetite, insomnia
Tx of depression, narcolepsy, and appetite suppression (in the past)
Amphetamine adverse
Fatigue and depression follow stimulation
Amphetamine other
releasing agents potentiate actions of endogenous NE by causing release from presynaptic vesicles
Methyphenidate other
releasing agents potentiate actions of endogenous NE by causing release from presynaptic vesicles
Tyramine other
releasing agents potentiate actions of endogenous NE by causing release from presynaptic vesicles
Methyphenidate Mechanism
Structural analog of amphetamine
Methyphenidate indication
Tx of ADHD in children
Tyramine Indication
Not clinically useful, found in fermented foods (cheese and wine)
Tyramine PK
Byproduct of tyrosine metabolism, normally oxidized by MAO
Tyramine Adverse
**Serious vasopressor episodes in patients on MAO-I’s after release of NE***
Cocaine Receptor
DAT
SERT
NET
Cocaine mechanism
Blocks dopamine (major effect), serotonin, and NE transporters -> potentiation and prolonged effects
Cocaine effect
Sympathomimetic
Therpeutic use: blockage of voltage gated sodium channels -> local anesthetic
Cocaine Adverse
Intense euphoria from blockage of dopamine reuptake in limbic system
Cocaine other
Monoamine reuptake inhibitor
Atomoxetine receptor
NET
Atomoxetine Mechanism
Selective NET inhibitor
Atomoxetine Indication
Tx of ADHD
Atomoxetine other
Monoamine reuptake inhibitor
Ephedrine receptor
alpha and beta
Ephedrine effect
Vasoconstriction and cardiac stimulation -> increase BP
Bronchodilation (prophylactic tx of asthma because it is slower onset and less potent than epi or isoproterenol)
Synergistic effect with Anti-AChE in treatment of myasthenia gravis
Mild CNS stimulation (alertness) and increased athletic performance
Pressor in spinal anesthetisa, works for MG; asthma
Ephedrine PK
NOT a catecholamine -> poor substrate for COMT and MAO -> longer duration of action
Excellent oral absorption, enters CNS
Eliminated unchanged in urine
Ephedrine Adverse
Herbal supplements banned in 2004 due to life threatening cardiovascular reactions
Ephedrine other
Induces release of NE* and activates adrenergic receptors*
Use declining due to better drugs with fewer side effects
Pseudoephedrine mechanism
ephedrine enantiomer
Pseudoephedrine receptor
alpha and beta
Pseudoephedrine effect
Nasal decongestant with an H1 histamine antagonist
Alpha antagonist drugs
Phenoxybenzamine Phentolamine Prazosin Terzosin Doxazosin Tamsulosin Yohimbine
alpha 1 blockers
-osins
Phenoxybenzamine receptor
non selective alpha
Phenoxybenzamine mechanism
alkylation irreversibly blocks receptor
slightly alpha one selective
Also blocks H1, M and 5-HT receptors; inhibits NET
Phenoxybenzamine effect
CVS: prevents vasoconstriction of peripheral blood vessels -> reflex tachycardia
Presynaptic alpha 2 block -> increase CO
Phenoxybenzamine indications
DOC Pheochromocytoma blocks effects of excess catecholamines (may require a beta blocker to control tachycardia after alpha blockade is established)
Historically used to lower BP, but was unsuccessful (block presynaptic alpha 2)
Phenoxybenzamine adverse
Postural hypotension Nasal stiffness Nausea and vomiting Inhibit ejaculation Contraindicated in patients with decreased coronary perfusion due to reflex tachycardia
Phenoxybenzamine contraindication
Patients with decreased coronary perfusion
Phentolamine receptor
nonselective alpha
Phentolamine mechanism
Reversible alpha blocker
Serotonin blocker
Muscarinic, H1 and H2 agonist
Phentolamine indications
Dx and control hypertensive episodes of pheochromocytoma
Prevents dermal necrosis when NE extravasates
**Antihypertensive in stimulant OD, sudden withdrawal of sympatholytics (clonidine), interaction between MAO-Is and tyramine*
Phentolamine adverse
Postural hypotension-baroreceptor reflex and alpha 2 blockade on cardiac nerves
Arrhythmia and angina
Contraindicated in patients with decreased coronary perfusion
Prazosin receptor
Selective alpha 1
Useful in treatment of HTN
Prazosin mechanism
decrease TPR through relaxation of arterial and venous smooth muscle
Prazosin effects
decrease BP without reflex tachycardia (alpha2)
Decrease LDL/TAG, increase HDL
Improves urinary blood flow
Prazosin Indications
Suppress sympathetic outflow from CNS
Tx of HTN, BPH
Prazosin Adverse
Not the DOC for primary HTN
First dose effect may cause exaggerated hypotensive response and syncope (adjust first dose 1/4 of normal)
Terazosin and Doxazosin receptor
Selective alpha 1
Useful for treatment of HTN
Terazosin and Doxazosin mechanism
Structural analog of prazosin -> longer half life -> less frequent dosing
Decrease TPR through relaxation of arterial and venous smooth muscle
Terazosin and Doxazosin effect
decrease BP without reflex tachycardia (alpha2)
Decrease LDL/TAG, increase HDL
Improves urinary blood flow
Tamsulosin effect
Relaxes genitourinary smooth muscle
Terazosin and Doxazosin indication
Suppress sympathetic outflow from CNS
Tx of HTN, BPH
Tamsulosin indication
Used in treatment of BPH with little effect on BP
reduced orthostatic HTN
Terazosin and Doxazosin adverse
Not the DOC for primary HTN
First dose effect may cause exaggerated hypotensive response and syncope (adjust first dose 1/4 of normal)
Tamsulosin adverse
Not the DOC for primary HTN
First dose effect may cause exaggerated hypotensive response and syncope (adjust first dose 1/4 of normal)
Tamsulosin receptor
Selective alpha 1
Treatment of HTN
Tamsulosin mechanism
Selective for alpha1A receptor found in genitourinary smooth muscle
Yohimbine receptor
alpha 2
Yohimbine mechanism
alpha 2 blocker -> indirect adrenergic agonist
Yohimbine effect
increase NE release -> increase BP
Yohimbine indication
treatment of erectile dysfunction, but has been replaced by PDE-5 inhibitors
Yohimbine contraindications
Can reverse effects of alpha 2 agonists (clonidine–bad!)
Beta antagonist drugs
Propranolol Nadolol Timolol Atenolol Metoprolol Esmolol
Propranolol receptor
Beta 1 and 2
Propranolol mechanism
CVS: decrease HR and contractility Increase TPR (beta 2)
Metabolic: decrease glycogenolysis and glucagon secretion -> severe hypoglycemia in patients on insulin
Propranolol indication/effect
Used in treatment of: HTN (through decreased CO, no the DOC) Migraine (blocks vasodilation) Hyperthyroidism Chronic angina (decrease O2 requirements) A-fib, MI (protective) Performance anxiety/stage fright (DOC)* Essential tremor
Propranolol Adverse
Bronchoconstriction->contraindicated in patients with COPD or asthma; variant angina
Impair recovery from hypoglycemia in insulin dependent patients -> syncope. Mask signs (ex. tachycardia seen in such episodes)
CNS: sedation, dizziness, lethargy, fatigue, depression
Propranolol other
Does not induce postural hypotension because alpha 1 receptors remain active
Reduce HDL, and increase LDL and TAGs (block activation of HSL) -beta 1 selectively actually improve the lipid profile
Abrupt withdrawal -> HTN
Nadolol indication/effect
long term treatment of angina and HTN
Timolol indication/effect
HTN, prophylaxis for migraines
Glaucoma (open angle)
Atenolol and Metoprolol indication/effect
Management of HTN in patients with impaired pulmonary function or IDDM
Atenolol and Metoprolol receptor
B1 cardioselective
Timolol receptor
Beta 1 and 2
Nadolol receptor
beta 1 and 2
Esmolol receptor
beta 1 cardioselective
Atenolol and Metoprolol other
less likely to produce bronchospasm
long term management of angina; s/p MI reduces mortality
Esmolol indication/effect
Useful in controlling arrhythmia (supraventricular or thyrotoxicosis), perioperative HTN, and MI in acutely ill patients
Esmolol other
Safer in critically ill patients
PK: ultra short acting, administer IV
Alpha 1 and Beta antagonists
Labetalol
Caverdilol
Labetalol receptor
alpha 1 and beta
Labetalol mechanism
Decrease in BP:
alpha 1 ->relaxation of arterial smooth muscle
beta 1 ->blocks sympathetic reflex
beta 2 -> sympathomimetic action contributes to vasodilation
Labetalol PK
more potent beta antagonist
Oral: chronic HTN
IV: emergencies
Labetalol Adverse
Orthostatic hypotension and dizziness (alpha 1)
Carvedilol indication/effect
used on patients with CHF and HTN
Carvedilol other
antioxidant properties
Pindolol receptor
partial beta agonist
Pindolol mechanism
Beta blocker with intrinsic sympathomimetic activity helps manage HTN
Pindolol indication / effect
causes a smaller reduction in resting HR and BP
Preferred in patients with diminished cardiac reserve or propensity to bradycardia
HTN in pregnant women
Alpha methyltyrosine
aka metyrosine
mechanism
Blocks NE and E synthesis through competitive inhibition of tyrosine hydroxylase
Alpha methytyrosine/ metyrosine indication/effect
used in adjuvant therapy with phenoxybenzamine in treatment of malignant pheochromocytoma (when surgery is not possible)
Reserpine (obsolete) mechanism
Irreversible damage to VMAT ->decrease NE and dopamine availability -> sympatholytic response
Reserpine indication/effect
Unable to concentrate and store NE and dopamine in the vesicle -> continuous breakdown by MAO
Decrease BP and HR
Reserpine other
historical treatment of HTN
Guanethidine mechanism
Uptake into nerve terminal via NET -> storage in vesicle and displacement of NE -> NE depletion
Guanethidine indication/effect
anti-hypertensive that was used in the early 1970s
Guanethidine adverse
orthostatic HTN and male sexual dysfunction
Guanethidine other
also disrupts the release of NE from the nerve terminal