EX2 Sympathomimetics/Beta agonists (P'col)

Mean arterial pressure equation

MAP = CO x TPR

Blood pressure = cardiac output x total peripheral resistance

Cardiac output equation

CO = SV x HR

Cardiac output = stroke volume x heart rate

Baroreceptor reflex

stretch of a blood vessel

Increased pressure, signal to brain to increase psym outflow, decrease symp outflow

a1/a2

activation → vasoconstriction (a2 minor role)

B2

activation → vasodilation

Beta receptors (heart)

B1/B2 in heart

B1 primary cardiac receptor

B2 heart failure

activation leads to increased SA, AV, and myocardium activity also increased CO

Alpha receptors (heart)

myocardium (hf)

minor increase in contractility

Epinephrine (what it does)

Agonist of a/B receptors

Potent vasopressor (increased vasoconstriction)

Increased all pressures, HR, CO, force

Dilates vessels, decreased peripheral resistance

Bronchodilation

Hyperglycemia

Epinephrine ADR/clinical note

Minor → restlessness (stimulant effects)

Serious → cerebral hemorrhage

Cardiac arrhythmias/angina

Use in patients on nonselective beta blockers result in unopposed activation → severe HTN

Still used as first line w/ patients using B-blockers

Epinephrine therapeutic uses

Hypersensitivity reactions → rapid relief of anaphylaxis (allergic reaction)

Bradyarrhythmias → Restore rhythm in patients with cardiac arrest

Asystole/pulseless cardiac arrest •

Ophthalmic uses → Mydriatic agent for ocular surgery/glaucoma, Mechanism is complex→ no longer commonly used for this purpose

Norepinephrine

similar to epinephrine, except doesn’t active B2

Increased BP

Psym like activity of heart (decreased)

Constriction of vasculature, increased peripheral resistance

Norepinephrine ADR

Greater elevation in BP (severe HTN)

Necrosis at injection site

Peripheral vasculature insufficiency

Norepinephrine therapeutic uses

raise/support BP

Cardiogenic shock

Septic shock (first choice vasopressor)

Spinal anesthesia

Dopamine

Metabolic precursor of NE and epinephrine

Central neurotransmitter → regulation of movement

Low concentrations → Agonist of D1 receptors

High concentrations → Agonist of beta 1 and alpha 1 receptors

Dopamine effects

Low dose (D1) → vasodilation of vasculature

Increased GFR, renal blood flow, natriuresis

Intermediate dose (B1) → increased HR, contractility, systolic pressure

High dose (a1) → vasoconstriction/increased peripheral resistance

Dopamine ADR

similar to EPI

Minor → anxiety, headaches, palpitations

Serious → angina pectoris, arrhythmias

Dopamine therapeutic uses

HF
Cardiogenic shock

Sepsis/septic shock

Beta agonists (nonselective)

Isoproterenol

Dobutamine

Beta 2 selective agonists (short acting)

albuterol

Beta 2 selective agonists (long acting)

salmeterol

formoterol

Beta 2 selective agonists (very long acting)

vilanterol

Beta 3 selective agonists

Mireabegron

Vibegron

Isoproterenol

nonselective B agonist

Decrease BP, increased CO, decreased vasculature

Bronchodilation

Isoproterenol ADR

Palpitations

Tachycardia

headache

flushing

Isoproterenol therapeutic uses

emergency stimulation of HR

Dobutamine

(-) isomer a1 agonist

(+) isomer is a1 antagonist

Both agonists of B receptors

Increased CO

Dobutamine ADR

May increase BP/HR (in patients w/ HTN)

Patients w/ a. fib. at risk

Dobutamine therapeutic uses

short term managements of cardiac decompensation

after cardiac surgery

congestive HF

acute myocardial infarction

Beta 2-selective adrenergic receptor agonists

Treatment of asthma/COPD

Bronchodilation

Reduced airway inflammation

Beta 2-selective adrenergic receptor agonists ADR

Tremor

Tolerance generally develops

Anxiety

Tachycardia

Albuterol

Short acting B2 selective agonist

Bronchodilation within 15 mins, duration 3-6H

Therapeutic use

Asthma

Symptomatic relief of bronchospasm

Salmeterol/formoterol

Long acting B2 selective agonist

Duration of action >12 hours (inhaled)

Salmeterol → Relatively slow

• Not suitable for treatment of acute

asthma symptoms

Formoterol → Bronchodilation within minutes

Used for COPD/nocturnal asthma

Shouldnt be used alone bc of ADR

Vilanterol

Very Long acting B2 selective agonist

Duration of action → 24 hours (inhaled)

Onset of action → 15 minutes

Used in combination inhalers with umeclidinium and/or fluticasone furoate → Not available for monotherapy

Therapeutic use COPD/asthma nocturnal

Mirabegron/vibegron

Beta 3-selective agonist

Relaxes bladder (increases capacity)

ADR HTN (mirabegron only)

UTIS/headaches

Therapeutic → urinary incontinence

Vibegron preferred in HTN patients

Phenylephrine

Potent, direct-acting alpha 1 agonist

Increased BP

Decreased HR

Vasoconstriction of vasculature, decreased blood flow

Therapeutic use → nasal decongestant, hypotension, opthalmic mydriatic agent

Oxymetazoline

A1 selective agonist

Direct acting vasoconstrictor

Therapeutic - nasal decongestant

ADR - rhinitis medicamentosa (rebound congestion) if used for more than 3 days

Ephedrine

mixed acting sympathomimetics

Direct/indirect agonist of alpha/beta

enhances release of NE

Ephedrine cardio/bladder/pulm/CNS

Increased BP

Increased HR/CO

Increased vasculature

Increased resistance to pee

Bronchodilation

CNS stimulant

Ephedrine adr/therapeutic use

HTN/insomnia

previously for asthma, supps got banned

Psuedoephedrine

mixed acting sympathomimetic like ephedrine

but more direct A1 agonist

Nasal decongestant

Cocaine

indirect acting sympathomimetic

inhibits reuptake of NE by inhibiting NET

Increased BP/HR

Leads to ADRs of arrhythmias, myocarditis, etc

Used for anesthesia of upper respiratory tract

Amphetamine (adderall)

Powerful CNS stimulant with peripheral sympathomimetic actions

Used for narcolepsy and ADH

Increased BP, contraction of urinary sphincter, very potent CNS stimulant

Dextroamphetamine

Greater CNS and less peripheral

Same therapeutic uses as amphetamine

Methamphetamine

Amphetamine-like sympathomimetics

Similar to amphetamine and ephedrine

More CNS effects

Shouldnt be used for narcolepsy or ADHD

Methylphenidate

Amphetamine-like sympathomimetics

Mild CNS stimulant

More on mental than motor

Narcolepsy/ADHD

Choices of agent in ADHD

Amphetamines more efficacious, methylphenidate better tolerated

SNRIs for children w/ history of substance abuse

Alpha 2 adrenergic agonist if poor ADRs of stimulants