Alpha and Beta Adrenergics Flashcards
Direct acting adrenergic receptor agonists
Dopamine (Intropin)
Norepinephrine (Levophed)
Epinephrine (Adrenalin)
alpha 2 receptors mainly mediate
cardio control center in the CNS (brain stem)
Beta 1 receptors mainly deal with what
heart (cardiac muscle), control renin release in the kidney
Beta 2 receptors mainly deal with what
smooth muscle vasculature, skeletal muscle blood vessels, bronchiole smooth muscle and uterine smooth muscle
direct acting alpha1 receptor agonists mediate
vasoconstriction and can also mediate pupil dilation (radial muscle under alpha1 control)
alpha 1 receptor agonists
Phenylephrine (Neosynephrine)
Methoxamine (Vasoxyl)
Oxymetazoline (Visine)
alpha 2 receptor agonists
Clonidine (Catapres) Methyldopa (Aldomet) Guanabenz (Wytensin) Guanfacine (Texex) Tizanidine (Zanaflex)
Non-selective beta receptor agonist
Isoproterenol (Isuprel)
Beta1-selective receptor agonists
Dobutamine (Dobutrex)
Dopamine (Inotropin)
Beta2-selective receptor agonists
Terbutaline (Brethine, Bricanyl) Metaproterenol (Metaprel, Alupent) Albuterol (Proventil, Ventolin) Salmeterol (Serevent) Ritodrine (Yutopar)
What is the EC50?
drug concentration at which 50% of the receptors are activated
cardiovascular effects of alpha1 agonists
vasoconstriction, which increases blood pressure
cardiovascular effects of beta1 agonists
expect increased heart rate, but baroreceptors increase vagal tone, which slows heart rate
cardiovascular effects of beta2 agonists
vasodilation, which decreases the blood pressure (drop in bp may also trigger baroreceptor reflex to increase heart rate)
effects of norepinephrine on heart rate
net effect = decreased heart rate
alpha1 agonist increases blood pressure but increases heart rate from beta1 agonist increases vagal tone, which decreases heart rate
effects of epinephrine on heart rate
observe expected increase in heart rate with beta1
alpha1 and beta2 essentially cancel out effects on blood pressure ( no change in BP)
effects of isoproterenol on heart rate
increase in heart rate
beta2 - decrease in blood pressure, increase heart rate
beta1 - increase in heart rate
What type of agonist is l-Norephinephrine (Levophed)
potent alpha and beta1 receptor agonist
What is l-Norephinephrine used for?
used as a pressor, drives blood pressure up, stimulates heart (slow/no change in heart rate)
What type of agonist is Ephinephrine (Adrenalin)?
potent alpha, beta1, and beta2 receptor agonist
What is Ephinephrine (Adrenalin) used for?
anaphylaxis, glaucoma, in combination with local anesthetics (vasoconstriction to keep anesthetic in area longer)
What type of agonist is Phenylephrine (Neo-Synephrine)?
potent alpha1 receptor agonist
very effective orally (not a substrate for COMT)
What is Phenylephrine used for?
nasal decongestant, mydriasis without cycloplegia (paralysis of ciliary muscle in eye), glaucoma, pressor (raises BP)
What type of agonist is Naphazoline (Privine)
partial agonist at alpha receptors
What type of agonist is Tetrahydrozoline (Visine)
partial agonist at alpha receptors
What type of agonist is Oxymetazoline (Afrin, Visine)
partial agonist at alpha receptors
alpha1 agonist side effects
changes in blood pressure (increase)
CNS stimulation at increased doses
What are Nephazoline, Tetrahydrozoline, and Oxymetazoline used for?
nasal and ophthalmic decongestants
OTC in nasal sprays
What is the concern with Nephazoline, Tetrahydrozoline, and Oxymetazoline?
Tachyphylaxis/Desensitization: causes alpha1 receptors to not respond as well long-term, can cause rebound congestion
What type of agonist is Clonidine (Catapres)?
selective alpha2 receptor agonist
Clinical effects of Clonidine
clinical effect linked to activation of alpha2 receptors in the nucleus of the solitary tract (cardiovascular center)
Uses of Clonidine
very effective anti-hypertensive agent, opiate withdrawal
How do alpha2 adrenergic agonists reduce blood pressure
by reducing sympathetic output from the brain
cardiovascular effects from the decreased sympathetic tone caused by alpha-adrenergic agonists
decreased heart rate, decreased contractility, decreased renin release, decreased vasoconstriction
Guanabenz (Wytensin) and Guanfacine (Tenex, Intuiv)
variants of Clonidine, used in hypertension and ADHD (guanfacine)
What is Methyldopa (Aldomet)?
a prodrug metabolized to active alpha2 receptor agonist, (1R, 2S)-alpha-methylnorepinephrine
Where does Methyldopa act?
acts at CNS alpha2 receptors to decrease sympathetic outflow
What is Methyldopa used for?
hypertension
Apraclonidine (Iopidine)
alpha2 receptor agonist
used in glaucoma
Tizanidine (Zanaflex)
alpha2 receptor agonist
used for muscle spasticity (alpha2 receptors in the spinal cord activate the reflex arc)
Adverse effects of alpha2-adrenergic receptor agonists
sedation, sodium and water retention, dry mouth, withdrawal symptoms
What kind of agonist is Isoproterenol (Isuprel)?
non-selective beta receptor agonist
What is isoproterenol used for?
asthma, chronic obstructive pulmonary disease, cardiostimulant
What type of agonists are Metaproterenol and Terbutaline?
selective beta2 receptor agonists
resorcinol derivatives
What are Metaproterenol and Terbutaline used for?
asthma, COPD; Terbutaline used as tocolytic (prevents premature labor)
What kind of effect can you observe only at high doses of Metaproterenol and Terbutaline?
cardiac effects
What type of agonist is Albuterol (Ventolin, Proventil) and Levalbuterol (Xopenex)?
selective beta2 receptor agonists
What is Albuterol/Levalbuterol used for?
short acting bronchodilation; asthma and COPD
What type of agonist is Salmeterol and Formoterol?
selective beta2 receptor agonist
How is Salmeterol/Formoterol different from albuterol?
Salmeterol/Formoterol are a long acting agents (not recommended for acute treatment of asthma symptoms)
How is Salmeterol/Formoterol used?
long acting bronchodilation; asthma and COPD
Different between Salmeterol and Formoterol?
onset of action:
Salmeterol - 10-20 min
Formoterol -
What is the net effect of Dobutamine (Dobutrex)?
positive inotropic effect on heart with little chronotropic effect (increases force of contraction with little increase in heart rate)
What is Dobutamine used for?
acute heart failure, shock
Where do indirect-acting sympathomimetrics act?
act at a target other than the receptor - causes a buildup of neurotransmitter
Name some indirect-acting sympathomimetics
amphetamine, pseudoephedrine, ephedrine, phenylpropanolamine, tyramine
How do indirect-acting sympathomimetics work?
promote release of NE via reverse action of plasma membrane transporter
Clinical uses of indirect acting sympathomimetics
amphetamines: ADHD, narcolepsy, anorexiant
others: nasal decongestants