EXAM #1: AUTONOMIC PHARMACOLOGY Flashcards
What is a selective direct acting adrenergic agonist?
- Direct acting= drug that directly agonizes an adrenergic receptor
- Selective= the drug is specific for a single type of adrenergic receptor e.g.alpha-1
What is a non-selective directing acting adrenergic agonist?
- Direct acting= drug that directly agonizes an adrenergic receptor
- Non-selective= drug is NOT specific for a single type of adrenergic receptor and can act on MULTIPLE types of adrenergic receptors
How will reserpine or guanethidine affect administration of a direct acting adrenergic agonist? What about cocaine?
- NO effect with reserpine or guanethidine
- Cocaine may potentiate the effects
What is a mix-acting adrenergic agonist?
Drugs that BOTH:
1) Increase the release of NE
2) Bind and activate adrenergic receptors
What drug is a mix-acting adrenergic agonist?
Ephedrine
How the the response of mixed-acting adrenergic agonists impacted by prior treatment by reserprine or guanethidine?
The response to the mixed agonist will be reduced compared to if it was given alone
What is an indirect acting adrenergic agonist? How will the response of an indirect-acting adrenergic agonist be impacted by prior treatment by reserprine or guanethidine?
Indirect agonist= drug that increases the AVAILABILITY of NE or Epi by a variety of methods
There will NOT be a response if there is pre-treatment with reserpine or guanethidine.
What are the three types of indirect-acting adrenergic agonists?
1) Releasing agents
2) Uptake inhibitors
3) MAO/COMT inhibitors
What class of drug is Phenylephrine?
Alpha-1 selective adrenergic receptor agonist
What are the clinical indications for Phenylephrine?
- Hypotension
- Rhinitis
- Paroxysmal atrial tachycardia
- As a Mydriatic
Why is Phenylephrine used for paroxysmal atrial tachycardia?
1) Causes an increase in mean BP
2) Reflex bradycardia will slow the atrial focus causing tachycardia
What are the alpha effects of Phenylephrine?
Activation of vascular smooth muscle increases BP and increase TPR
Note that there will be beta effects are high doses
List the alpha-2 selective adrenergic receptor agonists.
1) Clonidine
2) a-methyldopa
3) Apraclonidine
4) Brimonidine
What is the clinical indication for Clonidine and a-methyldopa?
Systemic hypertension
What is the clinical indication of apraclonidine and brimonidine?
Glaucoma
Note that despite being alpha-2 agonists, these drugs do NOT have a hypotensive effect
What is the mechanism of action of the alpha-2 selective adrenergic receptor agonists?
There are two mechanisms:
1) Activation of central alpha-2 receptors to decreases SNS outflow and blood pressure
2) Active alpha-2 receptors to decrease aqueous humor production and decrease intraocular pressure
What are the adverse effects of the alpha-2 selective adrenergic receptor agonists?
- Dry mouth (xerostomia)
- Sedation
- Hypotension
List the Beta-2 selective adrenergic receptor agonists.
Metaproterenol
Terbutaline
Albuterol
Ritodrine
What is the therapeutic use of metaproterenol?
1) Long-term treatment of obstructive airway disease, asthma
2) Acute bronchospasm
What are the characteristics specific to metaproterenol?
- Resistant to methylation by COMT
- B2 selective, but less than albuterol or terbutaline
What is the therapeutic use of Terbutaline?
1) Long-term treatment of obstructive airway disease
2) Acute bronchospasm
3) Emergency treatment of status asthmaticus (IV)
What are the characteristics specific to Terbutaline?
- Beta-2 selective
- NOT a substrate for COMT methylation
What is the therapeutic use of Albuterol?
1) Acute bronchospasm
2) Delay pre-term labor
What is the therapeutic indication for Ritodrine?
Uterine relaxation to:
1) Arrest premature labor
2) Prolong pregnancy
What are the adverse effects of B2 receptor agonists?
- Tachycardia
- Increased plasma glucose, lactate, and FFA
- Decreased plasma K+
- Tremors, restlessness, and anxiety
What increases the risk of tachycardia with B2 selective agoists?
- Pre-existing CAD or arrhythmia
- MAO inhibitor
What route of administration diminishes the risk of adverse effects of B-2 selective agonists?
Inhalation
What is the D1 selective receptor agonist?
Fendolopam
What is the clinical indication for Fendolopam?
Hypertensive crisis
What are the physiologic effects of Fendolopam?
Renal, mesenteric, periperal, and coronary vasodilation
Note that RBF is maintained and natriuresis is promoted
What is the side effect of Fendolopam?
Hypotension
List the non-selective adrenergic receptor agonists.
Isoproterenol Dobutamine Epinephrine Norepinephrine Dopamine
What receptors does Isoproterenol primarily interact with?
Beta 1 and 2
What are the clinical indications for Isoproterenol?
- Brady-arrhythmias
1) Bradycardia
2) Complete A-V block - Torsdes de pointes
- CHF as a positive ionotrope
- MI
Note that use during MI can lead to myocardial necrosis
What are the physiologic effects of Isoproterenol?
- Increased HR
- Increased myocardial contractility
- Decreased TPR
- Bronchodilation
What receptor does Dobutamine act on? What is the predominate receptor interaction at therapeutic doses?
Alpha-1
Beta-1
Beta-2
**Beta-1 is primary at therapeutic doses*
What are the clinical indications for Dobutamine?
1) Short-term treatment of cardiac failure
2) Stress test for CAD–drug induced
What are the cardiovascular effects of Dobutamine?
- Positive ionotorpe
- Positive chronotrope
Note that TPR is NOT affected*
What are the adverse effects of Dobutamine?
- HTN and tachycardia
- Increased ventricular response in a-fib
- Ventricular ectopy
- May increase size of MI
- Tolerance develops
What is the effect of epinephrine at low IV doses? Specifically, what receptors are implicated, and what are the receptor specific effects?
B1=
- Increased pulse pressure
- Increased HR
- Increased SV
- Increased CO
B2= vasodilation–>decreased TPR
What is the effect of epinephrine at intermediate IV doses? Specifically, what receptors are implicated, and what are the receptor specific effects?
Same beta 1 and 2 effects, PLUS:
Alpha-1= increased TPR and increased BP
*****Note that at moderate doses, beta-2 effects are counter acted by alpha-1 stimulation.
What is the effect of epinephrine at high IV doses?
- Mostly alpha-1 effects instead of beta i.e. increased TPR and BP
- Potential REFLEX BRADYCARDIA
Why does epinephrine initially have strong beta effects and then alpha effects at higher doses?
Beta receptors have a higher affinity for epinephrine; thus, they are saturated first
What is the purpose of subcutaneous epinephrine?
Epi is often a component of local anesthetics; it is included to:
- Cause vasoconstriction
- Vasoconstriction limits diffusion of the anesthetic
What is the epinephrine reversal phenomenon?
- Epinephrine activates both alpha and beta receptors
- Pretreatment with an alpha or beta antagonist will potentiate the effects of epinephrine via the alternate receptor type
What is the outcome of the epinephrine reversal phenomenon with alpha receptor antagonism?
Beta effects are enhanced:
- Vasodilation
- Decreased TPR
- Decreased MAP
What is the outcome of the epinephrine reversal phenomenon with beta receptor antagonism?
Alpha effects are enhanced:
- Vasoconstriction that is “unmasked”
- Dramatically increased MAP
What are the main sites of action of epinephrine in the vasculature?
Smaller arterioles and precapillary sphincters
What are the vascular effects of epinephrine?
Epinephrine causes the redistribution of blood flow
- Cutaneous blood flow is reduced
- Skeletal blood flow is increased
- Coronary blood flow is increased
- Little to no change in cerebral blood flow
- RBF is decreased
- GFR is unchanged
What happens to the filtration fraction with epinephrine administration? Why?
Increased
FF= GFR/RPF
GFR is unchanged but RPF decreases