Direct Acting Cholinergic Agonists
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Questions and Answers

What is the primary function of direct acting cholinergic agonists?

Mimic the effects of ACh by binding directly to cholinoreceptors (muscarinic or nicotinic)

What are the two groups of direct acting cholinergic agonists?

Endogenous choline esters and naturally occurring alkaloids

What is the effect of direct acting cholinergic agonists on the cardiovascular system?

Decreased heart rate, cardiac output, and blood pressure

What is the mode of action of indirect acting cholinergic agonists?

<p>Inhibit AChE, thereby indirectly providing a cholinergic action by preventing degradation of ACh</p> Signup and view all the answers

What are the two main categories of indirect acting cholinergic agonists?

<p>Reversible and irreversible</p> Signup and view all the answers

What is the primary use of edrophonium?

<p>Diagnosis of myasthenia gravis</p> Signup and view all the answers

What is the effect of physostigmine on the autonomic nervous system?

<p>Bradycardia, hypotension, and miosis, as well as contraction of visceral smooth muscle</p> Signup and view all the answers

What are some common adverse effects observed with cholinergic agonists?

<p>Diarrhea, diaphoresis, miosis, nausea, and urinary urgency</p> Signup and view all the answers

Which of the following direct acting cholinergic agonists has both nicotinic and muscarinic activity?

<p>Carbachol</p> Signup and view all the answers

What is the primary mechanism of action of indirect acting cholinergic agonists?

<p>Inhibiting the breakdown of acetylcholine</p> Signup and view all the answers

Which of the following indirect acting cholinergic agonists is used to diagnose myasthenia gravis?

<p>Edrophonium</p> Signup and view all the answers

What is the primary effect of pilocarpine on the eye?

<p>Miosis (constriction of the pupil)</p> Signup and view all the answers

Which of the following is a characteristic of endogenous choline esters?

<p>They include acetylcholine and synthetic esters of choline</p> Signup and view all the answers

What is the effect of bethanechol on the urinary system?

<p>Stimulation of the detrusor muscle</p> Signup and view all the answers

Which of the following indirect acting cholinergic agonists is used to manage symptoms of myasthenia gravis?

<p>Neostigmine</p> Signup and view all the answers

What is the primary effect of carbachol on the eye?

<p>Miosis (constriction of the pupil)</p> Signup and view all the answers

Study Notes

Direct Acting Cholinergic Agonists

  • Mimic the effects of ACh by binding directly to cholinoreceptors (muscarinic or nicotinic)
  • 2 groups: endogenous choline esters (ACh, bethanechol, carbachol) and naturally occurring alkaloids (nicotine, pilocarpine)
  • Longer duration of action than ACh
  • Limited clinical usefulness due to lack of specificity

Actions of Direct Acting Cholinergic Agonists

  • CVS: decrease in heart rate, cardiac output, and blood pressure
  • Smooth muscle: hyperactivity of GI tract and bronchiolar smooth muscle, stimulation of detrusor muscle (urination)
  • Exocrine glands: increase in secretions of sweat, saliva, tears, and bronchiolar secretions
  • Eye: miosis (constriction of the pupil) and decrease in intraocular pressure (for glaucoma)

Activity of Specific Direct Acting Cholinergic Agonists

  • Bethanechol: lacks nicotinic actions, strong muscarinic activity
  • Carbachol: both nicotinic and muscarinic activity
  • Pilocarpine: muscarinic activity, mainly used in ophthalmology

Indirect Acting Cholinergic Agonists

  • Inhibit AChE, leading to accumulation of ACh in synaptic cleft
  • Can provoke a response at all cholinoreceptors in the body, including muscarinic and nicotinic receptors of the ANS, NMJ, and brain
  • 2 groups: reversible (edrophonium, physostigmine, neostigmine) and irreversible (echothiophate)

Actions of Indirect Acting Cholinergic Agonists

  • Edrophonium (short-acting): used in diagnosis of myasthenia gravis
  • Physostigmine (intermediate-acting): enhancement of cholinergic transmission at NMJ, bradycardia, hypotension, miosis, contraction of visceral smooth muscle
  • Neostigmine (intermediate-acting): stimulates bladder and GI tract, used to manage symptoms of myasthenia gravis
  • Echothiophate: generalised cholinergic stimulation, paralysis of motor function, miosis

Adverse Effects of Cholinergic Agonists

  • Diarrhea, diaphoresis (increased sweating), miosis, nausea, urinary urgency

Direct Acting Cholinergic Agonists

  • Stimulate the parasympathetic nervous system (PNS)
  • Mimic the effects of Acetylcholine (ACh) by binding directly to cholinoreceptors (muscarinic or nicotinic)
  • Two groups: Endogenous choline esters and Naturally occurring alkaloids

Endogenous Choline Esters

  • Include ACh and synthetic esters of choline, such as bethanechol and carbachol
  • Have a longer duration of action than ACh
  • Show little specificity in their actions, limiting their clinical usefulness

Naturally Occurring Alkaloids

  • Include nicotine and pilocarpine
  • Have a longer duration of action than ACh
  • Show little specificity in their actions, limiting their clinical usefulness

Actions of Direct Acting Cholinergic Agonists

  • Cardiovascular system (CVS): decrease heart rate, cardiac output, and blood pressure
  • Smooth muscle: hyperactivity of GI tract and bronchiolar smooth muscle, stimulation of detrusor muscle (urination)
  • Exocrine glands: increase secretions of sweat, saliva, tears, and bronchiolar secretions
  • Eye: miosis (constriction of the pupil) and decrease in intraocular pressure (for glaucoma)

Individual Actions of Direct Acting Cholinergic Agonists

  • Bethanechol: lacks nicotinic actions, but has strong muscarinic activity
  • Carbachol: has both nicotinic and muscarinic activity
  • Pilocarpine: exhibits muscarinic activity, used mainly in ophthalmology

Indirect Acting Cholinergic Agonists

  • Inhibit Acetylcholinesterase (AChE), allowing accumulation of ACh in synaptic cleft
  • Can provoke a response at all cholinoreceptors in the body, including muscarinic and nicotinic receptors of the ANS, as well as the NMJ and in the brain

Types of Indirect Acting Cholinergic Agonists

  • Reversible: edrophonium, physostigmine, neostigmine
  • Irreversible: echothiophate
  • Reversible are further divided into short-acting and intermediate-acting

Actions of Indirect Acting Cholinergic Agonists

  • Edrophonium (short-acting): used in the diagnosis of myasthenia gravis
  • Physostigmine (intermediate-acting): enhancement of cholinergic transmission at NMJ, bradycardia, hypotension, miosis, contraction of visceral smooth muscle
  • Neostigmine (intermediate-acting): stimulates bladder and GI tract, used to manage symptoms of myasthenia gravis
  • Echothiophate: generalizes cholinergic stimulation, paralysis of motor function, miosis

Adverse Effects of Cholinergic Agonists

  • Diarrhea
  • Diaphoresis (increased sweating)
  • Miosis
  • Nausea
  • Urinary urgency

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Description

This quiz covers the characteristics and effects of direct acting cholinergic agonists, which mimic the effects of acetylcholine by binding to cholinoreceptors. It includes endogenous choline esters and naturally occurring alkaloids, and discusses their duration of action and specificity.

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