2. Adrenergics Flashcards
Sympathomimetics - Available Drugs
Epinephrine Norepinephrine Isoproterenol Dopamine Dobutamine Phenylephrine Metaproterenol Albuterol Salmeterol Terbutaline Ritodrine
Epinephrine - MOA
Agonist at a1, a2, b1, and b2 adrenergic receptors.
Epinephrine - Clinical Use
Anaphylaxis, glaucoma (open angle), asthma, hypotension
Norepinephrine - MOA
Agonist at a1, a2, and b1 adrenergic receptors.
Norepinephrine - Clinical Use
Hypotension (but decreases renal perfusion)
- Increase systolic BP due to effects on b1 increase on chronotropy and ionotropy of heart.
- Increase diastolic BP due to effects on a1 causing vasoconstriction
- Large BP increase will cause reflex bradycardia
Isoproterenol - MOA
Beta selective adrenergic agonist (b1 and b2)
Isoproterenol - Clinical Use
- AV block
- Bradycardia
- Transient increase systolic BP due to effects on b1 increase on chronotropy and ionotropy of heart. Overcome by vasodilatory effects and will drop slightly
- Decrease diastolic BP due to effects on b2 causing vasodilation
- Large BP decrease will cause reflex tachycardia
Dopamine - MOA
- D1 selective receptor agonist at low doses
- At medium doses also agonist at b1 and b2 adrenergic receptors
- At high doses also agonist at a1 and a2 adrenergic receptors
Dopamine - Clinical Use
- At low doses to increase renal perfusion in shock [D1 receptor]
- At medium doses for heart failure –> ionotropic and chronotropic [b1 and b1 receptors]
Dobutamine - MOA
Agonist at a1, a2, and b1 adrenergic receptors.
Dobutamine - Clinical Use
Heart failure, cardiac stress testing
- ionotropic and chronotropic
Phenylephrine - MOA
Alpha selective adrenergic agonist (a1 and a2)
Phenylephrine - Clinical Use
- Hypotension (vasoconstrictor)
- Ocular procedures (mydriatic)
- Rhinitis (decongestant)
Metaproterenol - MOA
Beta selective adrenergic agonist (b1 and b2)
Metaproterenol - Clinical Use
Acute asthma
Albuterol - MOA
Beta selective adrenergic agonist (b1 and b2)
Albuterol - Clinical Use
Acute asthma
Salmeterol - MOA
Beta selective adrenergic agonist (b1 and b2)
Salmeterol - Clinical Use
Long term treatment of asthma
Terbutaline - MOA
Beta selective adrenergic agonist (b1 and b2)
Terbutaline - Clinical Use
Reduce premature uterine contraction
Ritodrine - MOA
b2 selective adrenergic agonist
Ritodrine - Clinical Use
Reduce premature uterine contractions
Indirect Sympathomimetics - Available Drugs
Amphetamine
Ephedrine
Cocaine
Amphetamine - MOA
Indirect adrenergic agonist –> Causes release of stored catecholamines
Amphetamine - Clinical Use
Narcolepsy, obesity, ADD
Ephedrine - MOA
Indirect adrenergic agonist –> Causes release of stored catecholamines
Ephedrine - Clinical Use
Nasal decongestion, urinary incontinence, hypotension
Cocaine - MOA
Indirect adrenergic agonist –> Prevents reuptake of catecholamines
Cocaine - Clinical Use
Causes vasoconstriction and local anesthesia
Sympathoplegics - Available Drugs
Clonidine
a-Methyldopa
Sympathoplegics - MOA
Centrally acting a2-agonists –> decrease central adrenergic outflow
(Clonidine, a-Methyldopa)
Sympathoplegics - Clinical Use
Hypertension, especially with renal disease (does not decrease blood flow to kidney.
(Clonidine, a-Methyldopa)
Non-selective alpha Blockers - Available Drugs
Phenoxybenzamine (irreversible)
Phentolamine (reversible)
Phenoxybenzamine - MOA
Irreversible block of alpha adrenergic receptors
Phenoxybenzamine - Clinical Use
Pheochromocytoma, use before removal of the tumor
Phenoxybenzamine - Toxicities
Orthostatic hypotension, reflex tachycardia
Phentolamine - MOA
Reversible block of alpha adrenergic receptors
Phentolamine - Clinical Use
Give to patients on MAOi’s who eat tyramine containing foods (fava beans, aged cheese)
Phentolamine - Toxicities
Orthostatic hypotension, reflex tachycardia
a1 Selective Blockers - Available Drugs
Prazosin, Terazosin, Doxazosin
“-zosin”
a1 Selective Blockers - MOA
Selective blockade of the a1 adrenergic receptor.
Prazosin, Terazosin, Doxazosin
a1 Selective Blockers - Clinical Use
- Hypertension
- Urinary retention in BPH
(Prazosin, Terazosin, Doxazosin)
a1 Selective Blockers - Toxicities
- 1st dose orthostatic hypotension
- dizziness, headache
(Prazosin, Terazosin, Doxazosin)
a2 Selective Blockers - Available Drugs
Mirtazapine
Mirtazapine - MOA
Selective blockade of the a2 adrenergic receptor.
Mirtazapine - Clinical Use
Depression
Mirtazapine - Toxicities
Sedation, increased cholesterol, increased appetite
Effects of alpha Blockade on Epinephrine vs. Phenylephrine
Epinephrine has both alpha and beta effects. When combined with an alpha blocker the beta effects will win and the net result will be a depressor effect below baseline BP.
Phenylephrine has only alpha effects. When combined with an alpha blocker it has little or no effects and the net result will be a reversal of the pressor effect back to baseline BP.
b1 Selective Blockers - Available Drugs
Acebutelol, Betaxolol, Esmolol, Atenolol, Metoprolol
“A BEAM through the heart”
Non-selective beta Blockers - Available Drugs
Propranolol, Timolol, Nadolol, Pindolol
“Please Try Not (b)eing Picky”
Partial beta Agonists - Available Drugs
Pindolol, Acebutolol
“Partial Agonist - Pindolol, Acebutolol –> PAPA”
Non-selective alpha and beta Antagonists - Available Drugs
Carvedilol, Labetalol
Beta Blockers - Clinical Use
- Hypertension - decrease CO, decrease renin secretion (beta blockade on juxtaglomerular cells)
- Angina - Decrease HR and contractility resulting in decrease O2 consumption
- MI - Reduce mortality
- Supraventricular tachycardia (SVT) - Decrease AV conduction velocity (class II antiarrhythmic) [Propranolol and Esmolol]
- CHF - Slows progression of chronic failure - decrease cardiac dilation
- Glaucoma - Decrease secretion of aqueous humor [Timolol]
Beta Blockers - Toxicities
- Impotence, exacerbation of asthma, bradycardia, AV block, CHF, sedation, sleep alteration.
- Use with caution in diabetics - can decrease body’s response to hypoglycemia
b1 Selective Blockers - Advantage Over Other beta Blockers
Cardiac specific - Better to use in patients with comorbid pulmonary disease - Less chance of exacerbation due to b2 effects.
Partial beta Agonists - Advantage Over Other beta Blockers
Will have less of the negative cardiovascular side effects (ie less bradycardia)
