PNS Agonists(Cholinergic Drugs)

How do Cholinergic drugs affect the body?

stimulate the parasympathetic nervous system response

What is the primary neurotransmitter of the parasympathetic nervous system?

Acetylcholine

What are the effects of parasympathetic stimulation on the heart, lungs, and digestion?

• Heart: Decreased heart rate.

• Lungs: Bronchoconstriction and increased secretions.

• Digestion: Increased peristalsis and gastric secretions.

How does parasympathetic stimulation affect the pupils and the bladder?

• Eyes: Pupil constriction (miosis).

• Bladder: Bladder muscle contraction (promotes urination).

Why are these drugs dangerous for patients with asthma or COPD?

They cause bronchoconstriction, which can severely worsen breathing and close the airways.

Which patients would you not want taking a cholinergic drug because of the effect on the cardiovascular system?

Patients with hypotension and bradycardia.

How do direct-acting cholinergic agonists work?

They directly bind to and stimulate cholinergic receptors, mimicking the neurotransmitter acetylcholine.

What are the three examples of Direct-Acting Cholinergics? 

• Metoclopramide

• Pilocarpine

• Bethanechol chloride

What is the cholinergic-mediated effect of Metoclopramide in the GI tract?

It speeds up gastric emptying, which helps reduce nausea and vomiting.

What are the two main therapeutic uses for Pilocarpine?

1. To treat Glaucoma (by constricting the pupil to reduce intraocular pressure).

2. To treat dry mouth (by stimulating salivary production).

What is the main use for Bethanechol and what is its intended effect?

It is used to treat urinary retention. It works by contracting the bladder to promote urination

Name two absolute contraindications for Bethanechol.

1. Asthma (causes dangerous bronchoconstriction)

2. Urinary or GI obstruction (increases pressure behind the blockage)

What are example of Indirect-Acting Cholinergic drugs

• pyridostigmine

• edrophonium

• rivastigmine

• donepezil

How do indirect-acting cholinergic drugs like Donepezil work?

They inhibit the enzyme cholinesterase, which breaks down acetylcholine. This leads to more acetylcholine available to stimulate receptors.

What is the main therapeutic use for drugs like Donepezil and Rivastigmine?

To treat Alzheimer's disease.

What is the realistic goal of treatment for Alzheimer's with these drugs?

They do not cure the disease, but they help slow the progression of memory and cognitive decline.

What is the chronic medication Pyridostigmine used to treat?

Myasthenia Gravis. It helps improve skeletal muscle strength and tone.

How is Edrophonium used to diagnose Myasthenia Gravis?

It is an ultra-short-acting cholinesterase inhibitor used in the Tensilon test. If a symptom like ptosis (drooping eyelid) improves, the test is positive for Myasthenia Gravis.

What is the therapeutic goal of these drugs in Myasthenia Gravis?

To reduce the profound muscle weakness caused by the disease.

What is a "cholinergic crisis"?

It is an overdose of cholinergic drugs, leading to excessive stimulation of the parasympathetic nervous system.

What are the key symptoms of a cholinergic crisis? Remember "SLUDGE".

• Salivation

• Lacrimation (tearing)

• Urination

• Defecation / Diaphoresis (sweating)

• GI cramping

• Emesis (vomiting)

What is the specific antidote for a cholinergic crisis?

Atropine, which is an anticholinergic (cholinergic antagonist) drug.

What types of drugs will BLOCK or REDUCE the effects of cholinergic drugs?

• Anticholinergics (e.g., Atropine)

• Antihistamines (they have anticholinergic properties)

• Adrenergic Agonists (e.g., Epinephrine)

What is the danger of taking two cholinergic drugs together?

They have an additive effect, significantly increasing the risk of side effects and cholinergic crisis (SLUDGE).