Adrenergic Agonists And Antagonists

Front 1

Norepinephrine

Back 1

Receptor Selectivity α1, α2, β1
CV - α1 mainly
- Peripheral vasoconstriction--increase peripheral vascular rest.
- Inc BP
- Can cause reflex bradycardia (vagally mediated)

Therapeutic
-shock
-elevate bp during reduced symp tone

Front 2

Epinephrine

Back 2

Receptor Selectivity α1, α2, β1, β2
CV - high [] = α, low []=β agonist
- Incr HR, contractile force, cardiac output
- Inc systolic, dcr diastolic bp
- Const of most vascular beds but dilation of skel muscle blood vessel

Resp - Bronchdilation (Beta2)
Metabolic - Hyperglycemia, Lipolysis (beta2)

**Rapid relief of hypersensitivity rxns
Bradyarrythmis - restore rhythm in patients with cardiac arrest.

Front 3

Isoproterenol

Back 3

Receptor Selectivity β1, β2
CV
- Decr peripheral resistance
- Incr HR, Contractile force, CO
- Decr mean BP

Resp
-Bronchdilation
Tx
-In emergencies to stimulate HR in during bradycardia or heartblock

Front 4

Dopamine

Back 4

Receptor Selectivity - DA1, β1, α1
CV
- Low dose-- vasodilation of renal and mesenteric arteries - decr peripheral resistance!!
- Medium dose - Inrc hr, contractile force, cardiac output (B1)
- High dose - vasoconstriction and increase peripheral resistance (a1)

Tx: Severe congestive heart failure, shock

Front 5

Dobutamine

Back 5

Receptor Selectivity β1 agonist

CV:
-Incr cardiac rate, contactility and output
-Minimal change in peripheral resist and blood pressure

Front 6

Methyldopa

Back 6

Pro-drug - metabolized in adrenergic nerve terminals to α-methylnorepinephrine, which is sotred in nerve terminals and released with stimulation
--Potent α2 receptor agonist; reduces sympathetic out flow from the CNS
--Major therapeutic use-- Anti HTN

Front 7

Phenylephrine

Back 7

Acts on α1 adrenergic receptors
Increase systolic and diastolic bp
Decr HR (vagal reflex)
Decr Blood Flow - most vascular beds

TX: Opthalmic mydriatic, derc hemorrahge, conjuctival deconestion
-Nasal decongestant
-Used with local anesthetics to inrc duration of action
-Elevate BP

Front 8

Clonidine

Back 8

α2 selective adrenergic agonist
Major tx - anti htn agen (decr symp outflow)
-Reduces blood pressure by activating α2 receptors in the cardiovascular control centers in the CNS suppressing outflow of the symp nervous system from the brain.

Front 9

Albuterol

Back 9

Act mainly on β2 adrenergic receptors
Major tx - Bronchodialation --asthma

Front 10

Terbutaline

Back 10

Act mainly on β2 adrenergic receptors
Major tx - Bronchodialation --asthma

Front 11

Tyramine

Back 11

Pure Indirect-acting agent
-- Releases norepi from symp nerves ausing sympathomimetic actions
-- Found at high levels in certain foods
-- Normally metabolized to inactive products by MAO
-- MAOI + Tyramine = HTN crisis

Front 12

Amphetamine

Back 12

--Releases NE from adrenergic neurons
--Weak direct α & β receptor agonist
also weakly blocks Norepinephrine transporter (NET)
--Potent CNS stimulant
--Depresses Appetite
TX: Narcolepsy, ADD

Front 13

Ephedrine

Back 13

--Direct β2 agonist and releases NE that activates α and β1 receptors
--Has been used to tx asthma b/c of β2 agonist properties.
--Some herbal preparations contain ephedrine

Front 14

Pseudoephedrine

Back 14

--Direct α1 agonist activity with little β2 agonist activity
--less CNS stimulation
--Major TX: nasal decongestant (due to α1 agonist effects)

Front 15

Guanadrel

Back 15

--Anti HTN (essential HTN)
--Taken into adrenergic nerves by NET
-Taken up into storage granules and replaces NE; has no agonist activit and acts as a false transmitter
--Peripheral effects only -- no CNS penetration
Major Side Effects:
-- Orthostatic Hypotension
-- Interacts with Cocaine & tricyclics

Front 16

Reserpine

Back 16

Diffuses into adrenergic nerves
- Depetes nerves of NT by inhibiting the vesicular monoamine transporter 2 (VMAT2). Responsible for sequestering NE into storage vesicles.
-- Lipophilic so penetrates into CNS

Side effects: CNS depression--suicidal tendencies.

Front 17

Phenoxybenzamine

Back 17

Block α1 and α2 receptors
--Irreversible antagonist
--Long duration of action; blockade persists for daysl need to resynthesize the receptors
--Produces vasodialtion proportional to the degree of symp tone

Tx: Peripheral vascular disorders - Reynauds
Pheochromocytoma

Side eff: tachycardia and salt/water retention
orthostatic hypotension

Front 18

Effect on blood pressure: Epinephrine

Back 18

Mean pressure stays at 100, with wide pulse-pressure (100)

Mechanism:
1. Nonselectively stimulates both alpha and beta receptors
2. Beta1 receptors: Systolic blood pressure goes up
AND
Beta2 receptors: Diastolic blood pressure goes down (beta2 causes vasodilation)
3. Mean blood pressure stays the same
4. Pulse pressure is wide

HR: increase HR from beta1 (minor from beta2)