Unit 5 - Autonomic Nervous System Drugs Flashcards
What are ANS drugs?
Drugs that inc/dec ANS responses
What are the 3 mechanisms of ANS drugs?
- Mimic NT (and turn up response, direct or indirectly)
- Can inc amount of naturally occurring NT (enhance natural response)
- Some drugs bind to and block receptors (turn off response)
Can drugs act on both the SNS or the PNS? What can they be categorized as?
Never both, can be categorized as parasympathomimetics
Parasympatholytic
Sympathomimetics
sympatholytic
WHat are the 4 classes of ANS drugs, their physiological effect and an example
Cholinergics: Inc Parasymp effect> organophosphates
Anticholinergics: Dec parasymp effect > atropine
Adrenergics: Turn up symp effect > epinephrine, norepinephrine
Adrenergic blockers: Turn down symp response > Beta-blockers
What are cholinergic drugs?
drugs turn up PS response yb eithr mimicking ACh (indirect-acting)
action is inc binding to and turning on cholinergic receptors
overall effect is to inc PS activity
resting HR, RR, BP, dec contractility, bronchoconstriction
inc GI motility and GI secretions, urination, miosis, tearing
What are direct-acting cholinergic drugs and some examples?
drugs act like Ach and bind to and turn on cholinergic receptors
drug eventually degrades or diffuses away from synapse
EX: bethanecol - drug used to stimulate urination
Cisapride - Drug used to stimulate GI motility in cats with constipation
What are indirect acting cholinergic drugs and what are some examples of them?
Drugs block the activity of the acetylcholinesterase enzyme
^^ normally loc in the synaptic cleft and breaks down the NT > limits the PS response from going on too long/too much, blocking this enzyme causes the naturally occurring ACh to stay around longer
EX: organophosphates
What are organophosphates?
class of insecticide
indirect-acting cholinergic drug
Mechanism of action (on the insect): triggers activation of nicotinic receptors at NT junctions > Muscle spasms (skeletal muscle) leader to rigid paralysis
Also inc PS tone > severe bronchoconstriction
If OD or adverse reaction, can cause same effects in the host
Most common form of toxicity world-wide
What are anticholinergis?
drugs bind to and block cholinergic receptors
effect is PS response cannot be turned on = symp response dominates so inc HR, contractility, peripheral vasoconstriction, bronchodilator, dec GI motility and secretions, urine retention,
Common part of emerg drug kit
EX: atropine, glycopyrrolate
What is atropine?
anticholinergic
binds to and blocks ACh receptors > blocks PNS response
Physiological effects:
INC HR
blocks peripheral vasodilation (skin and GI) which results in inc BP and moves blood to support heart, lungs, kidney and brain
bronchodilator
mydrasis, dec secretions
What are the clinical uses of atropine?
CPR drug (give IV)
Given SQ as part of premed or intra-op to support HR and BP, dec airways secretions so easier to intubate
Tx’ing organophosphate toxicity
ophthalmic drops dilate pupils, dec tearing
What is glycopyrrolate?
synthetic anticholinergics
mechanism of action is similar to atropine, but longer acting and less pronounced effects
used as part of premet or intra op to support HR and BP, dec salivation and bronchial sections so easier to intubate, dec gastric fluids so lessens reflux
How do adrenergics work?
Turns on the symp response
work by binding to and turning on adrenergic receptors
effect depends on which receptors are targeted
What happens when Alpha 1 receptors are targeted by adrenergic?
blood vessels in skin and GIT; when activated, causes vasoconstriction of these vessels ? shifts blood flow so there is inc BP to heart/lung/brain
What happens when Alpha 2 receptors are targeted by adrenergic?
Sedatives
