Cholinergic Drugs Flashcards
Cholinergic Agonists: What happens when the nicotinic receptors are activated?
Muscle contraction
Cholinergic Agonist: What are responses when muscarinic receptors are activated?
Eye: Miosis (constriction of pupil)
Cardiovascular: Decrease in the heart rate
Respiratory: Bronchial Constriction and increased secretion
Gastrointestestinal: Increased motility; relaxation of sphincter
Genitourinary: Relaxation of sphincter and bladder wall contraction
Glands: Increased secretion
What is MOA?
Mechanism of Action
What is the MOA of Direct Acting Cholinergic Agonist?
They act by binding directly to cholinergic receptors
Example: Pilocarpine - Pilocar –> used to treat glaucoma
What is MOA of Indirect-Acting Cholinergic Agonists (Anticholinesterases)?
They inhibit the enzyme, acetylcholinesterase (AChE) whic terminates the action of acetylcholine. Thus they prolong the lifetime of acetylcholine… ***Enzyme may be inhibited either reversibly or irreversibly.
What are Reversible Inhibitors of acetylcholinesterase enzyme used for and how/why?
Used with Myasthenia Gravis (MG) in which there is an autoimmune destruction of acetylcholine receptors in the neuromuscular junction - **Edrophonium - Tensilon –> used in diagnosis of MG
— or —
Used in Alzheimer’s Disease in which there is a deficiency of cholinergic neurons. These drugs prolong the action of acetylcholine thereby reduce the loss of cognitive functioning in Alzheimer’s Disease - **Donezepil - Aricept
With Reversible Inhibitors of acetylcholinesterase enzyme, what drug is used for Myasthenia Gravis?
***Edrophonium (Tensilon)
Used when there is autoimmune destruction of acetylcholine receptors in neuromuscular junction
With Reversible Inhibitors of acetylcholinesterase enzyme, which drug treats Alzheimer’s?
***Donezepil (Aricept)
Used when there is a deficiency of cholinergic neurons. These drugs prolong the action of acetylcholine thereby reduce the rate of loss of cognitive functioning in Alzheimer’s disease…
What are Irreversible Inhibitors of acetylcholinesterase enzyme and what do they do?
They phosphorylate the enzyme cholinesterase and inactivate it permanently. Many are extremely toxic. Widely used as insecticides and commonly referred to as nerve gas.
The organophosphates are lipid soluble, they rapidly cross all membranes, including skin and blood-brain barrier. No therapeutic uses…
What are toxic symptoms of organophosphate poisoning?
SLUDGE
Salivation, Lacrimation, Urination, Diarrhea, GI Upset, Emesis (vomiting)
What two drugs are used to treat organophosphate poisoning? What is there MOA?
***Pralidoxime - hydrolyzes the phosphate bond and reactivates the enzyme.
***Atropine - blocks the effects of acetylcholine
What do Cholinergic Antagonists do?
These drugs antagonize (inhibit or block) the effects of acetylcholine.
- The most useful group selectively block muscarinic receptors of the parasympathetic nerves.
- Ganglionic blockers show a preference for the nicotinic receptors of the sympathetic and parasympathetic ganglia.
- Neuro-muscular blocking agents interfere with the transmission of efferent impulses to skeletal muscles. Used as skeletal muscle relaxant during anesthesia during surgery, intubation, and various orthopedic procedures.
What happens when you block the muscarinic receptors?
Eye - mydriasis (dilation of pupil), cycloplegia (results in blurred vision)
Skin - reduced sweating, flushing
GI - reduced motility and secretions
Cardiovascular - increased heart rate (high doses)
Respiratory - bronchial dilation and decreased secretion
GU- urinary retention
What are the side effects of cholinergic antagonists?
dry mouth, dry eyes, blurred vision, constipation, and urinary retention
What are common muscarinic antagonists?
- **Atropine - pre-anesthetic to prevent respiratory secretions, treatment of Parkinsonism, severe bradycardia
- **Scopolamine (Scopolamine) - used to prevent motion sickness (transdermal patch)
- **Ipratropium (Atrovent) - used to treat obstructive pulmonary disease (COPD) to produce bronchodilation
- **Trihexyphenidyl (Artane) - Parkinsonism
Drug classification and uses: Atropine
muscarinic antagonist
uses: pre-anesthetic to prevent respiratory secretions, treatment of Parkinsonism, severe bradycardia, enuresis
Drug classification and uses: Scopolamine (Scopace)
muscarinic antagonist
uses: to prevent motion sickness (transdermal patch)
Drug classification and uses: Ipratropium (Atrovent)
muscarinic antagonist
uses: chronic obstructive pulmonary disease (COPD) to produce bronchodilation
Drug classification and uses: Triheyphenidyl (Artane)
muscarinic antagonist
uses: Parkinsonism
Cholinergic Antagonist: What is the MOA of Neuromuscular Blockers?
These drugs block the effect of acetylcholine by interacting with the nicotinic receptors at the neuromuscular junction. They produce skeletal muscle relaxation. Clinically used during surgery for producing complete muscle relaxation.
Drug classification and uses: Succinylcholine (Anectine)
cholinergic antagonist; neuromuscular blocker
use: ideal for intubation because of rapid onset and short duration. Adjunct to anesthesia… Only depolarizing factors
Cholinergic Antagonists: Ganglion Blockers MOA
These drugs block the action of acetylcholine at the nicotinic receptors of all autonomic ganglia of both sympathetic and parasympathetic systems thereby blocking the entire output of the ANS - Rarely used clinicially
