Cholinergic and Anticholinergic Drugs

10 Questions

What is the effect of stimulating nicotinic synapses in the brain?

Increased vigilance, heightened mood

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

Inhibit the enzyme acetylcholinesterase, preventing the breakdown of ACh

What is the effect of cholinergic drugs on the pupils?

Constriction (miosis)

What is the indication for direct-acting cholinergic drug pilocarpine?

Glaucoma and intraocular surgery

What is the effect of cholinergic drugs on the heart?

Decreased heart rate

What is the term used to describe the effects of cholinergic drug overdose?

SLUDGE

What is the mechanism of action of echothiophate?

Irreversible covalent modification of acetylcholinesterase

What is the indication for indirect-acting cholinergic drug physostigmine?

Reversal of anticholinergic drug effects

What is the effect of cholinergic drugs on the respiratory system?

Bronchial constriction

What is the effect of cholinergic drugs on the gastrointestinal system?

Increased gastric secretions

Study Notes

Acetylcholine and Cholinergic Receptors

Acetylcholine is a neurotransmitter.
Cholinergic drugs can be classified into two types:
- Parasympathomimetic or cholinergic drugs: stimulate the parasympathetic nervous system (PNS).
- Parasympatholytic or anticholinergic drugs: block or inhibit the PNS.

Synthesis of Acetylcholine

Acetylcholine is synthesized from choline and acetyl CoA through the action of choline acetylase.
Acetylcholine is broken down into choline and acetate through hydrolysis catalyzed by acetylcholinesterase (AChE).

Types of Cholinergic Receptors

Nicotinic receptors: activated by nicotine, pentameric protein transmembrane channel, permeable to small cations.
Muscarinic receptors: activated by muscarine, single chain transmembrane protein, relays signals through G-proteins.

Effects of Nicotine and Nicotinic Agonists

Stimulate preganglionic neurons in the autonomic nervous system (ANS).
Increase heart rate and blood pressure.
Increase intestinal motility.

Autonomic Nervous System (ANS)

The ANS has two divisions: sympathetic (adrenergic) and parasympathetic (cholinergic).
The sympathetic nervous system prepares the body to deal with stress (fight or flight response).
The parasympathetic nervous system controls vegetative functions (e.g., constriction of pupils, slowing of heart rate).

Cholinergic Drugs

Mechanism of action:
- Direct-acting agonists: bind to cholinergic receptors, activating them.
- Indirect-acting agonists: inhibit acetylcholinesterase, increasing the availability of ACh at receptors.
Effects:
- Stimulation of intestine and bladder.
- Stimulation of pupils (miosis).
- Increased salivation and sweating.
- Cardiovascular effects: decreased heart rate, vasodilation.
- Respiratory effects: bronchial constriction, narrowed airways.

Adverse Effects and Indications

Adverse effects: "SLUDGE" (salivation, lacrimation, urination, diarrhea, gastrointestinal cramps, emesis).
Indications:
- Direct-acting drugs: reduce intraocular pressure, treat glaucoma and urinary retention.
- Indirect-acting drugs: treat myasthenia gravis, Alzheimer's disease.