Adrenergic Agonists Flashcards
Catecholamines differ in
- Oral usability
- Duration of action
- CNS penetration
Catecholamines are composed of
Catechol and ethylamine group
3 types of Adrenergic agnoists
Direct, indirect, mixed acting
How does tyramine act as a indirect acting sympathomimetic?
Tyramine displaces NA from cytoplasmic pool (sympathomimetic) -> taken by uptake 1 (NE transporter) into terminal then into vesicle by VMAT in exchange for NA which is taken up by uptake1 in exchange for tyramine. (if not metabolised by MAO)
What are direct acting catecholamines?
Non-selective catecholamines -> NA + AD
What are Indirect Acting Sympathomimetics?
Drugs that cause NA release in the absence of nerve stimulation
a1 direct acting agonists and usage
Oxymetazoline, phenylephrine
-> eye drops + runny nose
Noradrenaline is ______ in the gut
inhibitory
What is adrenaline reversal?
Presence of an a antagonist causes vasoconstrictor action to be blocked unmasking b2 mediated vasodilator -> fall in bp
Why are adrenaline stimulating drugs used during cardiac arrest?
Increases HR without bp change - no vagal drive to heart
Why are adrenaline stimulating drugs used for asthma?
b2 selective agonist -> bronchodilaton
Which adrenaline stimulating drug is used for cardiac arrests?
Dobutamine, b1 agonist
Why are adrenaline stimulating drugs used to treat glaucoma?
Reduces rate of aqueous humour prod. through a2 on ciliary body + veins (absorption)
Which adrenaline stimulating drug is used to treat glaucoma?
Dipivefrine (prodrug)
What type of glaucoma are adrenaline stimulating drugs used on?
open-angle (filtration angle between iris and cornea) simple glaucoma (intra-ocular pressure above 21mmHg)
What other drug can be used to treat open angle simple glaucoma?
Brimonidine, a2 agonist
What type of agonist is used during an anaphylactic shock? How is relief achieved?
Direct acting agonist, adrenaline. Counteracts laryngeal oedema, bronchospasm + hypotension (from histamine)
-> vasoconstriction through a1 reduces laryngeal oedema, b1 increase bp + bronchodilator (b2) Physiological antagonism
Adrenaline is used for vaso____ alongside ____ to prolong _____
constriction, LA’s, anaesthesia
Propranolol is more selective for
beta
Phentolamine is very selective for
alpha
Isoprenaline causes
vasodilation -> bp falls
-> tachycardia + direct b mediated force of contraction increases
Isoprenaline is very selective for
beta
Adrenaline is more potent on
beta than alpha
Adrenaline acts in
the adrenal medulla
Noradrenaline is more potent on
alpha than beta
Noradrenaline acts on
Post-ganglionic sympathetic nerve terminals
Isoprenaline causes smooth muscle to
relax
Dopamine is dose dependant. Which receptors are affected at different doses?
Low- D receptors
Med: B1 receptors
High: a1 receptors
Med + high doses can cause acute severe heart failure and hypertensive shock
Direct acting agonists are
selective
a2 direct acting agonists and usage
Clonidine -> hypertension + ADHD
B1 direct acting agonists and usage
Dobutamine for increase cardiac output
B3 direct acting agonists and usage
Mirabegron -> overreactive bladder
B2 direct acting agonists - short acting
Albuterol, terbutaline
B2 direct acting agonists - long acting
Salmeterol, formotorol
How do indirect acting agonists work?
Enhance NA + AD by inhibition of reuptake/breakdown
- > block reuptake of NA/dopamine in reward system
- > a1 + b1 -> increase BP + HR
Ephedrine
Mixed action agonist -> not catechloamine
- > direct binding, release of stored NA from pre-sympathetic terminals
- vasoconstriction
- bronchodilation
Pseudoephedrine
Mixed action agonist:
- > long duration
- > vasoconstriction and broncho muscle relaxation
- > nasal passages decrease mucus production
