Principles: Sympathomimetics

Question 1

What is the receptor effect profile of Epinephrine?

What are its clinical applications?

Answer 1

β > α

Direct sympathomimetic.

Used for anaphylaxis, open angle glaucoma, asthma, hypotension.

α effects predominate at high doses.

Question 2

What is the receptor effect profile of Norepinephrine?

What are its clinical applications?

Answer 2

α₁ > α₂ > β₁

Direct sympathomimetic.

Used for hypotension (but decreased renal perfusion)

Question 3

What is the receptor effect profile of Isoproterenol?

What are its clinical applications?

Answer 3

β₁ = β₂

Direct sympathomimetic.

Used for electrophysiologic evaluation of tachyarrhythmias.

Can worsen ischemia.

Question 4

What is the receptor effect profile of Dopamine?

What are its clinical applications?

Answer 4

D₁ = D₂ > β > α

Direct sympathomimetic.

Used for unstable bradycardia, heart failure, shock, ionotropic, and chronotropic α effects predominate at high doses.

Question 5

What is the receptor effect profile of Dobutamine?

What are its clinical applications?

Answer 5

β₁ > β₂ > α

Direct sympathomimetic.

Used for heart failure (inotropic > chronotropic), cardiac stress testing.

Question 6

What is the receptor effect profile of Phenylephrine?

What are its clinical applications?

Answer 6

α₁ > α₂

Direct sympathomimetic.

Hypotension (vasoconstrictor), ocular procedures (mydriatic), rhinitis (decongestant)

Question 7

What is the receptor effect profile of Albuterol?

What are its clinical applications?

Answer 7

β₂ > β₁

Direct sympathomimetic.

Acute asthma.

Question 8

What is the receptor effect profile of Salmetrol?

What are its clinical applications?

Answer 8

β₂ > β₁

Direct sympathomimetic.

Long-term asthma or COPD control.

Question 9

What is the receptor effect profile of Terbutaline?

What are its clinical applications?

Answer 9

β₂ > β₁

Direct sympathomimetic.

Reduce premature uterine contractions.

Question 10

What class of agent is Amphetamine?

How does it work?

What is it used for?

Answer 10

Amphetamine is an indirect general sympathetic agonist.

Monoamine reuptake inhibitor and releases stored catecholamines.

Used for narcolepsy, obesity, and attention deficit disorder.

Question 11

What class of agent is Ephedrine?

How does it work?

What is it used for?

Answer 11

Indirect general sympathetic agonist.

Releases stored catecholamines

Used for nasal decongestion, urinary incontinence, and hypotension.

Question 12

What class of agent is Cocaine?

How does it work?

What is it used for?

Answer 12

Indirect general agonist, reuptake inhibitor.

Used to cause vasoconstriction and local anesthesia.

Never give beta blockers if cocaine intoxication is suspected (can lead to unopposed alpha1 activation and extreme hypertension).

Question 13

Contrast the effects of norepinephrine and isoproterenol on blood pressure and heart rate.

Answer 13

Norepinephrine: α₁ > α₂ > β₁: Increases systolic and diastolic blood pressures through α₁-mediated vasoconstriction. Reflexive bradycardia from increased mean arterial pressure.

Isoproterenol: β₁ = β₂: Little alpha effect, causes B2-mediated vasodilation. Heart rate increases via B₁ activity and reflexive tachycardia due to decreased mean arterial pressure.

See graphs on page 249 for an illustration.

Question 14

What class of drug is Clonidine?

What is it used for?

Answer 14

Clonidine is an α₂ agonist.

Used for hypertensive urgency; does not decrease renal blood flow.

ADHD, severe pain, and a variety of off-label indications (ethanol and opioid withdrawal).

Question 15

What effects are seen during Clonidine toxicity?

Answer 15

CNS depression, bradycardia, hypotension, respiratory depression, small pupil size.

Question 16

What class of drug is α-methyldopa?

What is it used for?

Answer 16

α-methyldopa is an α₂ agonist.

Used for hypertension in pregnancy (safe during pregnancy)

Question 17

What effects are seen during α-methyldopa toxicity?

Answer 17

Direct Coombs positive hemolytic anemia.

SLE-like syndrome.

Question 18

What class of drug is phenoxybenzamine?

What is it used for?

What are effects of toxicity?

Answer 18

Phenoxybenzamine is a nonselective irreversible α-blocker.

Used for pheochromocytoma (preoperative) to prevent catecholamine (hypertensive) crisis.

Side effects: Orthostatic hypotension, reflex tachycardia.

Question 19

What class of drug is Phentolamine?

What is it used for?

Answer 19

Phentolamine is a nonselective reversible α-blocker.

Used for patients on MAO inhibitors who eat tyramine-containing foods.

Question 20

What is the common ending for α1-selective blockers?

What are they used for?

Answer 20

End in -osin. Examples: Prazosin, terazosin, doxazosin, tamsulosin.

Urinary symptoms of BPH; PTSD (prazosin); hypertension (except tamsulosin).

Question 21

Side effects of selective α₁ blockers?

Answer 21

α1 blockers are “-osin” ending (prazosin, terazosin, doxazosin, tamsulosin).

Side effects: 1st-dose orthostatic hypotension, dizziness, headache.

Question 22

What class of drug is Mirtazapine?

What is it used for?

What are its side effects?

Answer 22

Mirtazapine is a α₂ blocker.

Used for depression

Side effects: Sedation, increased serum cholesterol, increased appetite.

Question 23

How do epinephrine and phenylephrine affect blood pressure normally?
How about after an alpha-blockade?

Answer 23

Both cause a net pressor effect with no inhibition.

When alpha receptors are blocked, epinephrine causes a net depressor effect with a large dose (β₂ response).

Phenylephrine’s pressor effect is suppressed, pure α-agonist without β action.

See page 250 for graphs.

Question 24

Name the β₁ selective antagonists. (β₁ > β₂)

Answer 24

Acebutolol (partial agonist), atenolol, betaxolol, esmolol, metoprolol.

“Selective antagonists mostly go from A to M (β₁ with the 1st half of the alphabet).

Question 25

Name the nonselective beta blockers (β₁ = β₂)

Answer 25

Nadolol, pindolol, propanolol, timolol.

“Nonselective antagonists mostly go from N to Z (β₂ with 2nd half of alphabet).”

Question 26

Name the nonselective α and β antagonists.

Answer 26

Carvedilol and labetalol.

Nonselective α and β antagonists have modified suffixes (instead of -olol).

Question 27

What are the effects of Nebivolol?

Answer 27

Combines cardiac selective β₁-adrenergic blockade with stimulation of β₃ receptors, which activate nitric oxide synthase in the vasculature.

Question 28

Beta blockers can be used for anging pectoris.

What is their effect in this condition?

Answer 28

Reduce heart rate and contractility, result in a reduced oxygen consumption.

Question 29

What three beta blockers have been shown to reduce mortality during MI?

Answer 29

Metoprolol, carvedilol, and bisoprolol.

Question 30

What beta blockers are typically used during supraventricular tachycardia (SVT)?

What effect do they have?

Answer 30

Metoprolol and esmolol.

Decrease AV conduction velocity (class II antiarrhythmic)

Question 31

What effect do beta blockers have on hypertension?

Answer 31

Decrease cardiac output, reduce renin secretion (due to β₁-receptor blockade on JGA cells).

Question 32

What clinical effect do beta blockers have on CHF?

Answer 32

Slow progression of chronic failure.

Question 33

What beta blocker is typically used for glaucoma?

What effect does it have?

Answer 33

Timolol

Reduces secretion of aqueous humor.