Cholinomimetic drugs

Question 1

What are parasympathomimetic drugs?

Answer 1

agents that activate the parasympathetic nervous system (PSNS). They mimic the actions of acetylcholine (ACh), the neurotransmitter of the PSNS, and are also known as cholinomimetic agents.

Question 2

How are parasympathomimetic drugs classified?

Answer 2

Direct agonists: Bind directly to muscarinic or nicotinic ACh receptors, inducing responses similar to acetylcholine.

Indirect agonists (anticholinesterase inhibitors): Prolong the action of endogenous acetylcholine by inhibiting acetylcholinesterase (AChE), the enzyme that breaks down ACh.

Question 3

What are some uses of direct agonists?

Answer 3

Direct agonists are used topically in ophthalmology to induce miosis (constriction of the pupil).

Question 4

What conditions can indirect agonists treat?

Answer 4

postoperative ileus (lack of bowel movement after surgery), urinary retention, and myasthenia gravis (an autoimmune neuromuscular disorder).

Question 5

What are the functions of the parasympathetic nervous system

Answer 5

Protects the retina from excess light.
Decreases heart rate.
Promotes glandular secretions.
Promotes the emptying of hollow organs.
Promotes the conservation of energy.
Promotes rest and repair.
Physiologically antagonizes the sympathetic nervous system.

Question 6

What are some synonyms for parasympathomimetic drugs?

Answer 6

Cholinergic drugs
Acetylcholine receptor stimulants
Parasympathomimetics

Question 7

What are the two main types of receptors for cholinergic drugs?

Answer 7

muscarinic receptors: Drugs that bind to these receptors produce actions similar to muscarine and are G protein-linked receptors.

Nicotinic receptors: Drugs that bind to these receptors produce actions similar to nicotine and are ion channel-linked receptors.

Question 8

What are some examples of alkaloids that act as directly acting cholinergics?

Answer 8

Pilocarpine
Muscarine
Nicotine

Question 9

What are some examples of esters that act as directly acting cholinergics?

Answer 9

Acetylcholine
Carbachol
Methacholine
Bethanecol

Question 10

What are some examples of reversible anticholinesterase inhibitors?

Answer 10

Edrophonium
Physostigmine
Neostigmine

Question 11

What are some examples of irreversible anticholinesterase inhibitors?

Answer 11

Parathion
Soman
Echothiophate

Question 12

What are the muscarinic effects on the eye?

Answer 12

Stimulation of the iris sphincter muscle, causing miosis (pupillary constriction).

Contraction of the ciliary muscle, leading to the accommodation reflex for near vision.

Increased outflow of aqueous humor into the canal of Schlemm, reducing intraocular pressure.

Question 13

How do muscarinic effects impact the respiratory system?

Answer 13

Contraction of the smooth muscle of the bronchi, leading to bronchoconstriction.

Stimulation of tracheobronchial glands, increasing glandular secretions.

Question 14

How do muscarinic effects impact the cardiovascular system?

Answer 14

Reduced heart rate by decreasing SA node discharge and slowing AV conduction.

Vasodilation and decreased blood pressure due to the release of endothelium-derived relaxing factor.

Bradycardia and decreased blood pressure due to vagus nerve stimulation.

Question 15

What are the muscarinic effects on the gastrointestinal tract?

Answer 15

Stimulation of gut muscle contraction, increasing peristaltic activity.

Relaxation of the pyloric sphincter, potentially causing diarrhea.

Increased salivary and gastric gland secretion.

Question 16

What are the muscarinic effects on the genitourinary system?

Answer 16

Stimulation and contraction of the detrusor muscle in the bladder.

Relaxation of the trigone and sphincter of the bladder.

Facilitation of micturition (urination).

Question 17

What are the nicotinic effects on the neuromuscular junction?

Answer 17

They cause immediate depolarization of the end-plate of muscles, leading to muscle contraction due to increased membrane permeability to ions, primarily sodium (Na).

Question 18

What are the nicotinic effects on the autonomic ganglion?

Answer 18

Stimulation of sympathetic ganglia leads to raised blood pressure and tachycardia due to adrenaline release, while stimulation of parasympathetic ganglia causes symptoms like nausea, vomiting, and diarrhea.

Question 19

What is Bethanechol (Urecholine) used for?

Answer 19

Bethanechol is used to treat urinary retention and gastroesophageal reflux disease (GERD). It contracts bladder and stomach smooth muscles by acting on M3 receptors.

Question 20

What is Pilocarpine used for?

Answer 20

Pilocarpine eye drops are used to decrease intraocular pressure in glaucoma, and it also increases saliva production, which is helpful for relieving dry mouth caused by radiation therapy to the head and neck.

Question 21

What is Myasthenia Gravis?

Answer 21

Myasthenia Gravis is an autoimmune disease affecting the neuromuscular junction, characterized by symptoms such as ptosis, diplopia, difficulty in speaking and swallowing, extremity weakness, and potential respiratory muscle paralysis.

Question 22

How is Myasthenia Gravis diagnosed and treated?

Answer 22

It is diagnosed using the Edrophonium test and treated with Pyridostigmine (a long-acting anticholinesterase) and immunosuppressive drugs.

Question 23

What are the types of poisoning related to cholinergic drugs?

Answer 23

Muscarinic poisoning
Anticholinesterase poisoning
Nicotine poisoning

Question 24

What causes muscarinic poisoning and how is it treated?

Answer 24

Muscarinic poisoning is caused by overdoses of muscarinic drugs or ingestion of mushrooms containing muscarine. It is treated with gastric lavage, activated charcoal, atropine, and diazepam.

Question 25

What causes anticholinesterase poisoning and how is it treated?

Answer 25

Anticholinesterase poisoning is caused by organophosphates used as military nerve agents and insecticides.

It is treated by maintaining vital signs, preventing further poisoning, administering atropine and diazepam, and using prolidoxime to regenerate acetylcholinesterase.