Cholinergic Agents Flashcards
What is selectivity?
The degree to which a drug preferentially binds to a receptor subtype
At recommended doses, which drug is relatively selected for muscarinic receptors in the detrusor muscle of the urinary bladder and intestinal wall?
Bethanechol (Urecholine)
The internal urethral sphincter is under which type of control
Sympathetic
What type of receptor is found the internal urethral sphincter
Alpha-1
Which nerve innervates the external urethral sphincter? Sympathetic nerve? PS nerve?
Pudendal external
Symp hypogastric n.
PS pelvic n.
What types of receptors are found on the detrusor muscle
Beta-2 and muscarinic
Carbamylcholine
Mostly used uterine contractions pigs. Selective intestinal wall. Not a lot small animal. Gi atony.
Pilocarpine
Primary indication is to stimulate gland secretions. Decreases IOP. GIVE LOW dose because worry SLUD effects
Metaclopramide
Anti emetic. Promotes gastric motility. KCS
Edrophonium drug class, trade name, function
Tensilon, competitive reversible indirect acting cholinergic agent.
Bind to ACHE so that ACH can’t bind and get broken down
Prevent ach degradation, allows increased ACH bind to the few receptors left. Dx myasthenia gravis
Pyridostigmine trade and purpose
Mestinon, tx myasthenia gravis, maintenance
Physostigmine indications and drug class and toxic effects
Anticholinesterase or indirect acting cholinergic agent
Decrease IOP by causing miosis
Breakdown posterior synechia in horses
Treat gi atony in cattle subq
Can cross BBB since it’s non-ionized
Resp paralysis, vomiting, CNS depression, PS effects basically
How do you irreversible indirect acting cholinergic agents work
They covalently bonded to acetylcholinesterase permanently inactivating it
Organophosphates
Talk about major factors of organophosphate toxicities
Can cross blood brain barrier. Bronco constriction, airway secretions increased, abdominal cramping because of motility overdrive. Muscle tremors through the neuromuscular junction eventually lead to flaccid paralysis. This includes skeletal muscle needed to breathr. This leads to respiratory failure.
Name two agents to counteract irreversible ACHesterases. Talk about their mechanism of action
Pralidoxime tradename 2Pam it breaks the bonds between acetylcholinesterase and organophosphate. It binds to the organophosphate so that the body can eliminate it.This frees up ACHE to work again. Atropine is palliative care counters the intense parasympathetic affects
Atropine drug class and mechanism of action in treating ____ toxicity
Muscarinic receptor antagonist. @rec doses, It binds to cholinergic receptors until the body can eliminate organophosphates causing excess ACH
Anti-cholinergic effects usually referred to which type of agents?
Cholinergic receptor antagonists
Talk about atropine’s affects on the eye
It is often used for its cycloplegic effect. It relaxes the ciliary muscle. It inhibits parasympathetic innervation and there is unopposed sympathetic effect.
What are the parasympathetic affects on the ciliary muscle?
Causes the ciliary muscle to contract. The ciliary muscle is attached to the lens.It makes the lens into a CONE shape and puts the focal point in the near field.
What happens as a result of muscarinic antagonist at the ciliary muscle?
It relaxes the ciliary muscle. Lens flatten, and the focal point is in the distance. Common side effect is it blurry near vision
Does atropine cause the mydriasis or miosis? What does muscle does it affect?
It causes pupil dilation. unopposed sympathetic stimulation at the dilator muscle
Which cranial nerve carries parasympathetic innervation to the cranial organs
10
What is the effect at the AV node mediated by cholinergic and adrenergic receptors? What types of receptors?
Speed of conduction. Muscarinic and beta-1
What types of receptors are found on the heart? What is the effect at the SA node?
Muscarinic and beta-1. Heart rate
What type of agent should you use if you think that increased vagal tone is the source of the problem
Anti-cholinergic agents to block excess vagal tone
What should you give if you have a severe sinus bradycardia and decreased blood pressure? Under anesthesia
Atropine or glycopyrrolate
Anti-cholinergic agents are used with extreme caution in which species? Why?
Horses because it can cause ileus. Doesnt like in rabbits or ruminants. And ruminant CNS toxicities are common and there is potential for rumen stasis which can be fatal
Name an anticholinergic took that can cross the blood brain barrier and
Atropine
Name some CNS signs that can be seen as atropine
Anxiety restlessness disorientation
What drug is a good anti-cholinergic for C-sections? What makes it a good choice
Glycopyrrolate tradename Robinul-V. It’s more polar than atropine so it’s not going to cross the blood brain or placental barrier easily. It may be less likely to cause tachycardia
What kind of drug would you use to counteract an overdose of atropine and glycopyrrolate? Why
The problem is the inhibition of parasympathetic effects. You want to increase parasympathetic affects so you’re going to try to initiate an ACH flood so that it can compete for cholinergic receptors and overcome inhibition. You would use an anti-acetylcholinesterase
Name three endogenous catecholamines and 2 exogenous catecholamines
Endo norepinephrine epinephrine and dopamine. EXO isoproterenol and dobutamine
