Adrenergic Agonist/Antagonists Flashcards
Direct Acting Agonists (3)
- Epinephrine
- Norepinephrine
- Dopamine
Endogenous Catecheolamines
Epinephrine Effects
(7)
- Acts on both alpha and beta receptors
- Increases HR/Contractile force (b-1 effect)-increase O2 consuption by the heart
- Increases renin release (b-1)
- Constricts arterioles in skin and viscera (a-1)
- Dilates BV of skeletal muscle (b-2)
- Relaxes bronchiol smooth muscle (b-2)
- Increases glycogenolysis/lipolysis (b1,b2)
What happens when giving a pt a low dose of epi?
- PVR decreases d/t b-2 receptors are more sensitive to epi than a-1 receptors
- Diastolic pressure falls
- Systolic pressure increases d/t increases cardiac contractility (b-1)
- HR increases (b-1)
No increase in mean BP so the baroreceptor reflex does not kick in
What happens when giving a high dose of epi?
Uses as well
- Increase in ventricular contraction (b-1)
- Increase in HR (b-1)-opposed by the baroreceptor reflex
- Vasoconstriction (a-1)
Uses: anaphylactic shock, cardiac arrest, asthmatic attacks
Norepinephrine Effects
Alpha 1,2 and Beta 1
1. Peripheral vasoconstriction (a-1)
2. Increase cardiac contractility (b-1)
3. Increase in BP stimulates baroreceptors leading to reflex bradycardia
Tx: shock-increase BP
Isproterenol
Non-selective beta adrenergic agonist
1. Activates b-1/2
2. Increases HR, contractility, and CO (b-1)
3. Dilates arterioles of skeletal muscle (b-2)
4. Diastolic pressure decrease-systolic remains unchanged (could go up)
5. Bronchodilation (b-2)
6. Used in emergencies to stimulate HR in pt’s with HB and bradycardia
Dobutamine
Beta-1 Selective Adrenergic Agonist
1. Potent inotrope-mild chronotropic effects
2. Less increase in HR and decrease in PVR than isoproterenol
3. Mild vasodilation
4. Increase in cardiac O2 consumption-stress echocardiogram
Management of Acute HF, cardiogenic shock
Albuterol
Beta-2 Adrenergic Agonist
1. Causes bronchodilation
2. Used with ICS in asthma
3. DOC for acute asthma attacks
Salmeterol/Formoterol
Beta-2 Adrenergic Agonist
Prolonged duration compared to albuterol
Used in asthma
Mirabegron
Beta-3 adrenergic agonist-detrusor muscle relaxation and increases bladder capacity
Tx: Overactive bladder, urinary incontinence
Moderate CYP2D6 inhibitor
Adverse effects of Mirabegron
- Increase BP
- Increased UTI
- Headache
Phenylephrine
Alpha-1 adrenergic agonist
1. Vasoconstriction
Uses:
1. Nasal decongestant. Given PO/topical
2. Mydriasis
3. Tx of hypotension from vasodilation in anesthesia
NO CYCLOPLEGIA
Clonidine
Alpha-2 Adrenergic Agonist
CENTRALLY ACTING ANTIHYPERTENSIVE
1. Activates central presnypatic alpha-2 adrenoceptors which reduces sympathetic outflow thus reducing BP
Adverse effects of Clonidine
- Lethargy
- Sedation
- Xerostomia
Methyldopa
Activates central alpha 2 adrenoceptors
* Drug of choice for Tx of hypertension in pregnancy
Methylphenidate
Unknown mechanism
Increases Norepi and dopamine reuptake inhibitor
Tx: ADHD in kids
Atomoxetine
Selective inhibitor of NET
Tx: ADHD in kids
Modafinil
Psychostimulant
Inhibits norepinephrine and dopamine transporters
Tx: Narcolepsy
Adverse effects of Methyldopa
(3)
- Sedation
- Impaired mental concentration
- Xerostomia
Brimonidine
Highly selective alpha 2 agonist
Tx: lower intraocular pressure in glaucoma (reduces aqueous humor production and increase outflow)
Amphetamine
Indirect Acting Adrenergic Agonist- RELEASING AGENT
Causes norepinephrine release by reversing monoamine transporters
Uses: ADHD, Narcolepsy
CNS stimulatory action
Can increase BP, stimulatory effects on heart
Cocaine
Indirect Acting Adrenergic Agonist-UPTAKE INHIBITOR
Monoamines accumulate in synaptic space-potentiation and prolongation of their central and peripheral actions
Blocks voltage-activated sodium channels
Sympathetic effects like tachycardia, HTN, peripheral vasoconstriction, pupil dilation
*Most potent at blocking DAT (dopamine transporter)-higher concentrations block SERT and NET
SERT=5-HT transporter
NET=Norepi transporter
Tyramine
Indirect Acting Adrenergic Agonist- RELEASING AGENT
Found in fermented foods-normally oxidized by MAO.
- Causes release of catecholamines by reversal of NET (Norepi transporter)
If taken w/ MAO-Massive Vasopressive effects
Ephedrine
Mixed Acting Adrenergic Agonist
Used as a pressor agent during spinal anaesthesia
Tx: Adjunct therapy in myasthenia gravis
Not a catecholamine but penetrates CNS
Pseudoephedrine
Sudafed
Mixed Acting Adrenergic Agonists
-Nasal decongestant
Phenoxybenzamine
Non-selective alpha Adrenergic Blocker
1. Irreversible antagonist
2. Not good for HTN
Uses: Prior to surgery for pheochromocytoma or for management of inoperable tumors
Phentolamine
Non-Selective Alpha Adrenergic Blocker
1. Reversibly blocks alpha 1/2 receptors
Uses:
1. Dx of/management of pheochromocytoma (phentolamine blocking test= Decrease in BP = pheochromocytoma)
2. Prevention of dermal necrosis aftra extravasation of norepinephrine
3. HTN crisis d/t stimulate OD
Epinephrine Reversal
Alpha adrenergic blockers reverse epinephrine effect but vasodilation of Beta-2 receptors not blocked.
Systemic BP decreases in response to epi given in the presence of phenoxybenzamine
Prazosin, Terazosin, Doxazosin
Selective blocker of Alpha-1 adrenergic receptors
Uses:
1. HTN (not drugs of choice)
2. BPH-drug of choice for symptom relief-relaxes smooth muscle
3. First dose can have exaggerated hypotensive response so small first dose (1/4, 1/3) for first three meds
Prazosin=prototype
Tamsulosin
Treatment for Benign Prostatic Hyperplasia
Selective Alpha-1A receptor (predominates in GU smooth muscle).
- Minimal effect on BP
- Less likely to cause orthostatic hypotension
Propranolol, Nadolol, Timolol
Beta Adrenergic Blockers
CVS effects: slow HR and decrease myocardial contractility
Respiratory: contraindicated for pts with asthma
Metabolic: decrease glycogenolysis, glucagon secretion
Propranolol=prototype
Atenolol/Metoprolol/Esmolol
Selective Beta-1 Adrenergic Blockers
- impaired pulmonary fx
- diabetic pts
Esmolol: ultra short half life, used for rapid control of ventricular rate
Pindolol
Partial beta-Agonist
Preferred in individuals w/ diminished cardiac reserve or a propensity to bradycardia
Labetalol/Carvedilol
Alpha-1, Beta-selective Blockers
Labetolol: substantially more potent b-antagonist than alpha. (Competitive)
Carvedilol: Antioxidant properties. Used for HTN/CHF
Timolol
Tx for glaucoma-diminish intraocular pressure
Beta blocker uses (10)
- HTN
- Glaucoma (timolol)
- Migraine prophylaxis
- Hyperthyroidism-blunt sympathetic stimulation
- Angina-chronic management
- A Fib-control ventricular rate
- Myocardial infaction-protective effect
- Prevention of bleeding from esophageal varices
- Performance Anxiety
- Essential Tremor
Beta-blocker adverse effects
Hypoglycemia
Nonselective beta blockers impaire recovery of hypoglycemia d/t blockade of beta-2 receptors in liver
Also mask tachycardia seen in hypoglycemia (early warning sign)
Beta blocker adverse effect
Lipid Metabolism
Inhibit release of free fatty acids from adipose tissue
1. Increase TAGs
2. REduce HDL
Both negative impact
Can you withdraw from beta blockers abruptly?
No-should be taper to avoid tachycardia, htn, ischemia (rebound effect d/t increased receptor count)
Methyltyrosine (Metyrosine)
Competitive inhibitor of tyrosine hydroxylase (Inhibit norepi synthesis)
- Management of malignant pheochromocytoma
- Preop preparations for pheochromocytoma
Reserpine
Irreversibly blocks VMAT-vesicles that store norepi/dopamine
- Gradual decrease in BP and HR
- Treated HTN in the past
Valbenazine
Reversible inhibitors of VMAT
Tx of tardive dyskinesia
Tetrabenazine
Reversible inhibitors of VMAT
Tx of chorea in Huntington’s Disease
Contraction of the pupillary dilator (radial) in the iris has what function and receptor?
Mydriasis
Alpha 1 receptor
Contraction of the pupillary constrictor (sphincter) muscle in the iris causes has what function and receptor?
Miosis
M3 receptor
Contraction of the ciliary muscle has what function?
And receptor
Adapts to short range focus (M3)
What is the function of ciliary epithelium?
Produce aqueous humour
Receptors: Beta2, alpha2, D1-3, FP (prostaglandins)
Latanoprost
Activates FP receptors to increase uveoscleral outflow decreasing intraocular pressure
FP=prostaglandin
Acetazolamide, dorzolamide
Inhibition of carbonic anyhdrase reduces formation of aqueous humor thus decreasing intraocular pressure
Overview table of ocular hypotensive drugs
Common Autonomic Adverse Effects
Muscarinic agonists, AChE inhib, Antimuscarinics, Stimulants
