Sympathetic drugs Flashcards
Other than being taken back up into the presynaptic neuron, some NE can be broken down by _____________
Monoamine oxidase (MAO) and catechol-O-methyltransferase
An example of drug action on the synthesis of NE
Methyldopa acts as a ‘false transmitter’ that reduces NE production and creates a different metabolite that causes sympathetic inhibition.
An example of drug action on the storage of NE
Resperine blocks the uptake into storage vesicles of NE so when the stored up NE runs out there is no more left to be used.
An example of drug action on the release of NE
Bretylium blocks the release of NE at the synapse decreeing the amount available.
An example of drug action on the uptake/reuptake of NE
Imipramine inhibits reuptake of NE causing it to remain in the synapse longer.
Beta 1 agonists are often used to treat _________
Cardiac disease
Epinephrine in general is used to treat _________
Anaphylactic reactions
Beta 2 agonists are often used to treat _________
Obstructive airway disease
Alpha 2 agonists are often used for _________
Sedation/analgesia
Beta 1 antagonists are often used to treat _________
tachyarrhythmias
Alpha 1 antagonists are often used to treat _________
vasodilation (?)
Alpha 2 antagonists are often used as _________
reversals for Alpha 2 sedation
What are catecholamines?
endogenous substances that serve as hormones/neurotransmitters
**positive ionotropes (contractility)
What are 5 examples of catecholamines?
Epinephrine Norepinephrine Isoproterenol Dopamine Dobutamine
What receptors are targeted by epinephrine and what is it used for?
All adrenergic receptors. Alpha 1 - vasoconstriction Alpha 2 Beta 1 - cardiac contraction (cardiac arrest) Beta 2 - bronchodilation (anaphylaxis) Beta 3 -
Epinephrine mode of delivery?
IV, IM, SC.
NOT given orally because it is rapidly metabolized by the GI tract.
T/F Catecholamines generally cross the BBB
FALSE.
Catecholamines generally do not cross the BBB
When to be cautious using epinephrine?
Glaucoma, non-anaphylactic shock, combined with other drugs effecting the heart, Tachycardia/tachyarrhythmias.
What type of drug is epinephrine?
Catacholamine - Direct acting sympathomimetic
Norepinephrine mode of delivery?
Given intravenously.
What receptors are targeted by norepinephrine?
Mainly alpha receptors but also beta 1.
NOT beta 2.
What is norepinephrine used for?
It will increase mean arterial blood pressure, increase after load of the heart, and be a potent vasoconstrictor due to lack of beta 2 involvement.
Cautions for using norepinephrine?
Combined with other drugs effecting the heart, and avoid extravasation (injecting outside of the blood vessel could cause tissue damage).
What type of drug is norepinephrine?
Catacholamine - Direct acting sympathomimetic
What receptors are targeted by isoproterenol?
Beta 1 and Beta 2
Isoproterenol mode of delivery?
Injectable solution.
What is isoproterenol used for?
Rarely used anymore. SYNTHETIC
Increases heart contractility, increases oxygen consumption, decreases vascular resistance, and bronchiole relaxation.
Cautions using isoproterenol?
Can lead to tachycardia/tachyarrhythmias
What drug would be better to use in the short term to treat bradyarrhythmias, isoproterenol (catecholamine) or atropine (antimuscarinic)
Atropine.
Which receptors does dopamine target?
Alpha and Beta-1. Dose dependent (Alpha 1 not involved until medium dose achieved)
Dopamine mode of delivery?
IV infusion due to short half life.
What effect will dopamine have at a low dose?
Dilation of vascular beds (renal, mesenteric, etc)
What effect will dopamine have at a medium dose?
Activates alpha 1 and promotes increased contractility.
What effect will dopamine have at a high dose?
Activated alpha 1 receptors cause release of NE and vasoconstriction.
*not used for anaphylaxis as much as other catecholamines.
Cautions when using dopamine?
Combined with other drugs effecting the heart (lead to tachyarrhthymia) and avoid extravasation (injecting outside of the blood vessel could cause tissue damage).
What type of drug is dopamine?
Catacholamine - Direct acting sympathomimetic.
What receptors are effected by Dobutamine?
Beta 1 mainly
Dobutamine mode of delivery?
IV infusion due to short half life.
What is dobutamine used for?
Increased heart contractility and heart rate.
Cautions with dobutamine
Combined with other drugs effecting the heart (lead to tachyarrhthymia) and avoid extravasation (injecting outside of the blood vessel could cause tissue damage).
What kind of drug is dobutamine?
Catecholamine - Direct acting sympathomimetic.
Phenylephrine targets which receptor?
Alpha 1 agonist
Phenylephrine mode of delivery?
Oral, IV, IM, intranasal, ophthalmic
Phenylephrine can be used systemically or locally to induce __________
vasoconstriction and increase vascular resistance
Phenylephrine can be used ophthalmically to induce __________
mydriasis and and diagnose horner’s syndrome (sympathetic lesion)
Cautions when using Phenylephrine?
- Less effective in cats and horses.
- Systemic effects (increased vasoconstriction) can occur when used topically in small patients.
- Reflex bradycardia
What kind of drug is phenylephrine?
Non-catecholamine Direct acting sympathomimetic