Sympathetic Stimulators (Sympathomimetics)

Question 1

What are the 3 categories of sympathomimetics?

Answer 1

1. Adrenergic
2. Alpha agonists
3. Beta agonists

Question 2

Adrenergic Effects

Answer 2

1. Stimulate heart rate, contractility, and conduction (beta 1)
2. Core vasodilate to ↑ blood flow to brain, heart, and skeletal muscle (beta2); vasoconstrict everywhere else (alpha 1)
3. Inhibit GI & GU function
4. Inhibit most secretions
5. Bronchodilate in the lungs (beta2)

Question 3

Catecholamines

Answer 3

1. Parental only
2. short duration of action
3. cannot cross blood-brain barrier
   ex: dopamine, norepinephrine, and epinephrine

Question 4

Noncatecholmines

Answer 4

1. can be oral
2. metabolized slowly by enzyme MAO-longer half-life
3. more able to cross blood-brain barrier
   ex: ephedrine, amphetamine, phenylephrine

Question 5

What are Adrenergic meds used for?

Answer 5

1. Asthma: dilation of bronchioles (beta 2)
   (does not affect respiratory rate)
2. Eye exams: dilation of pupils = mydriasis
3. Pre-term labor: relaxation of pregnant uterus
4. Urinary Antispasmodics: relaxation of detrusor muscle of bladder & contraction of bladder neck (↓ voiding).
5. Heart & BP control: Alpha & Beta stimulators/blockers.
6. Parkinson’s: dopaminergic

Question 6

Epinephrine

Answer 6

1. Effects alpha and beta
2. catecholamine
3. IV, SC, and inhalation (nebs)
4. Uses- cardiac arrest, anaphylatic shock, acute allergic reactions, aute asthma attacks, and added to anesthetics
5. ADRs- excessive cardiac and CNS stimulation

Question 7

Dopamine

Answer 7

“low dose”: 1-2 mcg/kg/min -dopaminergic. Used to promote renal perfusion and urinary output. (renal dosing)
MAP should be 60 or greater for this to be working (kidney perfusion, 30 ml per hour Urinary Output)

“mid dose”: 5-10 mcg/kg/min stimulates primarily beta receptors with some alpha. Strengthen cardiac output

“high dose”: >20 mcg/kg/min stimulates alpha receptors- Not often, probably going to die.
Used often for someone who’s blood pressure has dropped.

Question 8

norepinephrine

Answer 8

Uses: severe hypotension

ADR: SEVERE vasoconstriction→ HTN, angina, kidney failure.

Question 9

Primarily Beta

Answer 9

1. Beta 1: used to improve cardiac function
   dobutamine IV
2. Beta 2: used to improve respiratory function via bronchodilation; usually given via inhalers
   -albuterol
   -metaproterenol
3. Both Beta 1 and Beta 2
   isoproterenol IV

The higher the dose and/or the longer the therapy, the less receptor-specific the effect.

Question 10

Beta ADRs

Answer 10

ADRs: depends if agonist (↑)/antagonist (↓)
1. Beta 1 effects heart rate
ex: Beta 1 agonist will increase heart rate
Beta 1 antagonist will decrease heart rate
2. Beta 2 glucose and tremors

Question 11

Alpha 2 Agonists

Answer 11

Mechanism: Central stimulation of alpha 2 receptors in CNS (not periphery). Vasodilates.

Uses: anti-hypertensives, peds may use for ADHD

Drugs include
clonidine PO (ADHD- helps them sleep), (Patches- only for BP used for elderly)
methyldopa PO

ADRs: orthostatic hypotension