Cholinergic Pharmacology Overview

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Questions and Answers

What is a potential consequence of using mucosal decongestants excessively?

Ischaemic damage to the mucosa (correct)

Reduced nasal congestion

Enhanced drug absorption

Increased ciliary activity

What should be prioritized in the treatment of shock?

Increasing oxygen supply alone

Administering antibiotics

Replacement of fluids lost from circulation (correct)

Immediate surgical intervention

What is a recommended practice regarding the use of sympathomimetic vasoconstrictors?

Use for more than three weeks

Limit use to a few days (correct)

Increase the dosage when symptoms persist

Use for at least two weeks to assess efficacy

Which substance is NOT mentioned as a mucosal decongestant?

Pseudoephedrine 0.5% Signup and view all the answers

Which of the following is a vital function affected by shock?

Consciousness and respiration Signup and view all the answers

In what situation should antimuscarinic drugs be avoided when considering their use for mydriasis?

When prolonged action is not necessary Signup and view all the answers

What effect do neonicotinoids primarily have?

Nicotine-like effects on neurons Signup and view all the answers

Which of the following conditions can antimuscarinic agents be used to address?

Bladder spasm after urologic surgery Signup and view all the answers

Which of the following drugs does NOT have significant nicotinic effects at clinical doses?

Bethanechol Signup and view all the answers

What side effect can occur with higher concentrations of atropine?

Dry mouth Signup and view all the answers

What mechanism do cholinesterase inhibitors use to enhance the effects of acetylcholine?

They inhibit the enzyme that breaks down acetylcholine. Signup and view all the answers

What is the primary role of nonspecific or pseudo cholinesterase in the body?

To destroy various esters in tissues, including plasma. Signup and view all the answers

What is a contraindication for the use of antimuscarinic drugs?

Glaucoma Signup and view all the answers

Which drug is primarily used to lower intraocular pressure in chronic simple glaucoma?

Pilocarpine Signup and view all the answers

What therapeutic application is NOT appropriate for antimuscarinic agents?

Treatment of chronic kidney disease Signup and view all the answers

Which of the following effects occur due to cholinergic stimulation of cholinoceptors in the eye?

Meiosis and ciliary muscle spasm. Signup and view all the answers

What clinical risk is associated with cholinergic drugs in asthmatic patients?

Increased bronchoconstriction and mucosal hyper-secretion. Signup and view all the answers

Which drug is a selective M3 receptor antagonist used for urinary disorders?

Oxybutynin Signup and view all the answers

In the context of cholinergic drugs, what does 'parasympathomimetic' refer to?

Drugs that stimulate parasympathetic nerves Signup and view all the answers

What is a common side effect of antimuscarinic agents seen in adults?

Tachycardia Signup and view all the answers

Which of the following accurately describes the action of a direct-acting cholinomimetic?

It binds and activates cholinoceptors mimicking acetylcholine's effects. Signup and view all the answers

What is the primary action of muscarinic agonists?

Binding to muscarinic receptors Signup and view all the answers

Which of the following statements about organophosphate aging is correct?

It makes the organophosphate binding to cholinesterase more permanent. Signup and view all the answers

In elderly men, what condition should antimuscarinic drugs be used with caution?

Prostatic hyperplasia Signup and view all the answers

What are the potential effects of a cholinergic crisis?

Skeletal muscle weakness and parasympathetic effects. Signup and view all the answers

What is the effect of cholinergic stimulation on the gut?

Increased motor activity and potential colicky pain. Signup and view all the answers

Why is acetylcholine not used in therapeutics despite its importance?

It is rapidly destroyed by cholinesterase. Signup and view all the answers

Which effect is NOT associated with cholinergic stimulation of the heart?

Increased cardiac output. Signup and view all the answers

Which of the following best characterizes cholinomimetic alkaloids?

They are weakly alkaline and resemble acetylcholine's effects. Signup and view all the answers

What is the characteristic feature of a partial agonist drug?

Produces a smaller effect than a full agonist Signup and view all the answers

Which drug is considered an irreversible alpha receptor antagonist?

Phenoxybenzamine Signup and view all the answers

What is the primary effect of alpha-receptor antagonists on blood pressure?

Lower peripheral vascular resistance Signup and view all the answers

Which of the following is a common clinical use for alpha-receptor antagonists?

Chronic Hypertension Signup and view all the answers

Which beta-receptor antagonist has intrinsic sympathomimetic activity (ISA)?

Pindolol Signup and view all the answers

What is orthostatic hypotension primarily caused by?

Inadequate blood volume Signup and view all the answers

What distinguishes beta-receptor antagonists in clinical use?

They have various affinities for B1 and B2 receptors Signup and view all the answers

Which condition is NOT typically treated with alpha-receptor antagonists?

Diabetes Mellitus Signup and view all the answers

Study Notes

Nonspecific Esterases

Present in various tissues, including plasma
Not specific for acetylcholine but also break down other esters

Cholinergic Stimulating Effects on Organs

Eye: Miosis (constriction of pupil), ciliary muscle spasm (accommodation for near vision), decreased intraocular pressure.
Exocrine Glands: Increased secretion of salivary, lachrymal, bronchial, and sweat glands.
Heart: Bradycardia (slow heart rate), atrioventricular block, potential cardiac arrest.
Bronchi: Bronchoconstriction, hypersecretion of bronchial mucus (potentially serious in asthmatic patients).
Gut: Increased motor activity, colicky pain, increased secretions.
Bladder and Ureters: Contraction, promoting micturition (urination).
Neuromuscular Junction: Activation, causing muscle fasciculation (muscle twitching).

Cholinergic Drugs

Choline Esters: Cholinomimetic drugs consisting of choline or a choline derivative esterified with an acidic substance (e.g., acetic or carbamic acid). Typically poorly lipid-soluble.
Cholinomimetic Alkaloids: Drugs with weakly alkaline properties (usually an amine of plant origin) mimicking acetylcholine's effects. Usually lipid-soluble.
Direct-Acting Cholinomimetics: Bind and activate cholinoceptors, mimicking acetylcholine's effects.
Indirect-Acting Cholinomimetics: Amplify endogenous acetylcholine's effects by inhibiting acetylcholinesterase.

Cholinergic Subtypes

Muscarinic Agonist: A cholinomimetic drug binding muscarinic receptors, exhibiting primarily muscarine-like actions.
Nicotinic Agonist: A cholinomimetic drug binding nicotinic receptors, exhibiting primarily nicotine-like actions.

Cholinesterase Inhibitors

Organophosphates: Esters of phosphoric acid inhibiting cholinesterase.
Organophosphate Aging: Organophosphates, after binding to cholinesterase, chemically modify and become more firmly bound to the enzyme.
Parasympathomimetics: Drugs resembling the effects of stimulating parasympathetic nerves.

Cholinergic Drug Types

Direct-Acting: Receptor agonists.
- Choline esters: Examples: acetylcholine, carbachol, bethanechol.
- Alkaloids: Examples: nicotine, pilocarpine.
Indirect-Acting: Cholinesterase inhibitors, or anticholinesterases.
- Examples: physostigmine, neostigmine, pyridostigmine, donepezil.
- Inhibit the enzyme that destroys acetylcholine, allowing endogenous acetylcholine to persist and intensify effects.

Antimuscarinic Drugs

Examples: Atropine, ipratropium, oxybutynin.
Block muscarinic receptors.
Therapeutic uses:
- Respiratory disorders: reduce airway secretions, treat asthma.
- Cardiovascular disorders: treat bradycardia.
- Gastrointestinal disorders: relieve abdominal colic, traveler's diarrhea, and hypermotility.
- Urinary disorders: relieve bladder spasm, improve bladder capacity, and continence.
- Other applications: reduce hyperhidrosis (excessive sweating).

Antimuscarinic Side Effects and Contraindications

Side effects: dry mouth, mydriasis (pupil dilation), tachycardia (rapid heart rate), hot and flushed skin, agitation, delirium.
Contraindications: glaucoma, elderly men with prostatic hyperplasia (BPH), pyloric stenosis, bladder neck obstruction.

Salmeterol

Bronchodilator with long-duration of action.

Mucosal Decongestants

Nasal and bronchial decongestants (vasoconstrictors): Used in allergic rhinitis, colds, coughs, and sinusitis.
Examples: ephedrine, phenylephrine, xylometazoline (Otrivine).
Excessive use can lead to mucosal damage, rebound congestion.

Shock

A state of inadequate capillary perfusion of vital tissues, leading to oxygen deficiency and impaired function of vital organs (heart, brain, kidneys).
Treatment: address the underlying cause (e.g., bleeding, infection), replace lost fluids, perfuse vital organs, maintain blood pressure and blood flow.

Alpha Receptor Antagonists

Examples: phentolamine, prazosin, terazosin, doxazosin, tamsulosin, alfuzosin, phenoxybenzamine.
Block alpha receptors.
Pharmacological Effects:
- Cardiovascular: Lower peripheral vascular resistance, reduce blood pressure.
- Other: miosis, nasal stuffiness.
Clinical Uses:
- Pheochromocytoma (tumor releasing norepinephrine and epinephrine).
- Hypertensive emergencies.
- Chronic hypertension.
- Peripheral vascular disease.
- Local vasoconstrictor excess.
- Urinary obstruction.
- Erectile dysfunction.
- BPH.

Beta Receptor Antagonists

Examples: propranolol, metoprolol, atenolol.
Block beta receptors.
Different types: some have higher affinity for beta1 receptors (affecting the heart) while others have higher affinity for beta2 receptors (affecting the lungs).

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Description

This quiz covers the role of nonspecific esterases and the effects of cholinergic stimulation on various organs. It also includes a section on cholinergic drugs, focusing on their mechanisms and impacts on the body. Test your understanding of these critical pharmacological concepts!