Pharmacology 4th Lecture
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Questions and Answers

Where are neural nicotinic receptors located?

  • In the neuromuscular junction
  • In the brain
  • In autonomic ganglia (correct)
  • In the spinal cord

    • What is the mechanism of action of cholinergic antagonists?

  • They trigger an intracellular response
  • They bind to cholinergic receptors but do not trigger an intracellular response (correct)
  • They inhibit the release of acetylcholine
  • They stimulate the nicotinic muscle receptor

    • What type of receptors do anti-muscarinic drugs compete with acetylcholine for?

  • Dopaminergic receptors
  • Adrenergic receptors
  • Muscarinic receptors (correct)
  • Nicotinic receptors

    • What is the effect of ganglionic blockers on the nervous system?

    <p>They inhibit the nicotinic neuronal receptor</p> Signup and view all the answers

    What is the effect of neuromuscular blockers on the nervous system?

    <p>They inhibit the nicotinic muscle receptor</p> Signup and view all the answers

    Where are muscular nicotinic receptors located?

    <p>In the neuromuscular junction</p> Signup and view all the answers

    What type of receptor does atropine block competitively?

    <p>Muscarinic receptors</p> Signup and view all the answers

    Which type of classification is pirenzepine an example of?

    <p>Selective M1-blocker</p> Signup and view all the answers

    What is the source of atropine?

    <p>Atropa belladonna plant</p> Signup and view all the answers

    What is the half-life of atropine?

    <p>4 hours</p> Signup and view all the answers

    Where does atropine not cross?

    <p>Blood-brain barrier</p> Signup and view all the answers

    What is the duration of atropine's action when placed topically in the eye?

    <p>Days</p> Signup and view all the answers

    What is the mechanism of action of atropine?

    <p>Competitive reversible blockade of ACh at muscarinic receptors</p> Signup and view all the answers

    What type of alkaloids are atropine and scopolamine?

    <p>Natural Alkaloids</p> Signup and view all the answers

    What is the mechanism of action of non-depolarizing neuromuscular blockers?

    <p>They competitively block cholinergic transmission at the nicotinic receptors.</p> Signup and view all the answers

    What is the therapeutic use of succinylcholine?

    <p>As an adjuvant drug for general anesthesia.</p> Signup and view all the answers

    What is the duration of action of succinylcholine when given as a single dose?

    <p>3 to 6 minutes</p> Signup and view all the answers

    What is a side effect of neuromuscular blockers?

    <p>Bronchoconstriction and hypotension</p> Signup and view all the answers

    Which of the following is a non-depolarizing neuromuscular blocker?

    <p>Tubocurarine</p> Signup and view all the answers

    What is the route of administration for all neuromuscular junction blockers?

    <p>Intravenous (I.V.)</p> Signup and view all the answers

    What is the mechanism of action of succinylcholine?

    <p>Opening of Na+ channels, leading to membrane depolarization</p> Signup and view all the answers

    What is the treatment for malignant hyperthermia?

    <p>Blocking the release of Ca++ from the sarcoplasmic reticulum</p> Signup and view all the answers

    What is a ganglionic blocker?

    <p>Trimethaphan</p> Signup and view all the answers

    What is the adverse effect of succinylcholine that can be life-threatening?

    <p>Malignant hyperthermia</p> Signup and view all the answers

    What is the effect of atropine on the extrapyramidal system in patients with parkinsonism?

    <p>It reduces the rigidity</p> Signup and view all the answers

    Why is atropine used in pre-anaesthetic medication?

    <p>To decrease salivary and bronchial secretions</p> Signup and view all the answers

    What is one of the therapeutic uses of atropine in the treatment of cardiac conditions?

    <p>Heart block due to myocardial infarction</p> Signup and view all the answers

    Which of the following anticholinergics is used in the treatment of peptic ulcer?

    <p>Pirenzepine</p> Signup and view all the answers

    What is the therapeutic use of Scopalamine in the treatment of motion sickness?

    <p>Orally or a patch behind the ear</p> Signup and view all the answers

    What is one of the therapeutic uses of atropine?

    <p>Nocturnal Enuresis</p> Signup and view all the answers

    What is the effect of atropine on the respiratory centre?

    <p>It counteracts the inhibitory effect of Morphine</p> Signup and view all the answers

    What is one of the therapeutic uses of atropine in the treatment of gastrointestinal conditions?

    <p>Gastrointestinal spasm</p> Signup and view all the answers

    What is the effect of atropine on the vestibular system?

    <p>It blocks M receptors</p> Signup and view all the answers

    Which of the following is a therapeutic use of benzotropine and trihexyphenidyl?

    <p>Treatment of Parkinsonism</p> Signup and view all the answers

    What is the adverse effect of atropine that is especially prominent in children?

    <p>Hyperthermia</p> Signup and view all the answers

    Which of the following is a contraindication for atropine?

    <p>Enlarged prostate</p> Signup and view all the answers

    What is the use of emepronium?

    <p>To reduce bladder motility and increase capacity in cases of urinary incontinence</p> Signup and view all the answers

    Why is hyoscine preferred over atropine as a pre-anaesthetic medication?

    <p>It has stronger antisecretory activity</p> Signup and view all the answers

    What is the effect of ipratropium?

    <p>It produces bronchodilatation without decreasing secretions</p> Signup and view all the answers

    What is a common adverse effect of atropine?

    <p>Urinary retention</p> Signup and view all the answers

    Study Notes

    Nicotinic Receptors

    • Nicotinic receptors are of two types: Neural nicotinic (Nn) located in autonomic ganglia, and Muscular nicotinic (Nm) located in the neuromuscular junction.

    Cholinergic Antagonists (Parasympatholytics)

    • Cholinergic antagonists bind to cholinergic receptors (M/N) but do not trigger an intracellular response.
    • Muscarinic blockers: inhibit efferent impulses to skeletal muscle via the nicotinic muscle receptor (Nm).
    • Ganglionic blockers: inhibit the nicotinic neuronal receptor (Nn) of both parasympathetic and sympathetic ganglia.

    Antimuscarinics

    • Antimuscarinics are drugs that compete with Ach for muscarinic receptors.
    • Classification: according to selectivity, they can be non-selective (e.g., Atropine) or selective (e.g., pirenzepine, a selective M1 blocker).

    Antimuscarinic Classification

    • Classification according to their nature:
      • Natural alkaloids: Atropine and Scopolamine (hyoscine).
      • Synthetic atropine substitutes: used as mydriatics, antiasthmatics, antispasmodics, and for urinary incontinence and parkinsonism.

    Atropine

    • Atropine is a belladonna alkaloid that binds competitively and prevents Ach from binding to its sites.
    • Acts both centrally and peripherally, with a duration of action of about 4 hours.
    • Pharmacokinetics: readily absorbed, partially metabolized by the liver, and eliminated primarily in urine, with a half-life of about 4 hours.
    • Pharmacodynamics: causes competitive reversible blockade of ACh at muscarinic receptors, and also has an effect on the extrapyramidal system, reducing the rigidity of patients with parkinsonism.

    Therapeutic Uses of Atropine

    • In pre-anaesthetic medication to decrease salivary and bronchial secretions, prevent lung collapse and bronchopneumonia, and protect the heart from excessive vagal tone.
    • As an antispasmodic for intestinal, renal, and biliary conditions.
    • Treatment of severe bradycardia and syncope associated with hyperactive carotid sinus reflex.
    • Hyperhidrosis (excessive sweating), anti-Parkinsonism, peptic ulcer, nocturnal enuresis, and antidote to parasympathomimetics.

    Atropine Substitutes

    • Mydriatics: cyclopentelate, homatropine, and eucatropine.
    • Antisecretory: pirenzepine and telenzepine.
    • Antispasmodic: Hyoscine butyl bromide (Buscopan).
    • Antiparkinsonian: Benztropine and Trihexyphenidyl (Artane).

    Adverse Effects and Toxicity of Atropine

    • Dry mouth, blurred vision, tachycardia, constipation, urine retention, increased IOP, flush, agitation, delirium, and hyperthermia.
    • In acute toxicity, patient is "dry as a bone, blind as a bat, red as a beet, and mad as a hatter".

    Contraindications of Atropine

    • Glaucoma.
    • Enlarged prostate (benign prostatic hyperplasia).

    Hyoscine (Scopolamine)

    • Therapeutic uses: pre-anaesthetic medication, prophylaxis of motion sickness, sedative in cases of mania, and antiemetic.

    Nicotinic Antagonists

    • Neuromuscular blockers: Tubocurarine, gallamine, and succinylcholine.
    • Ganglionic blockers: Trimethaphan, hexamethonium, and mecamylamine.

    Neuromuscular Blockers

    • Classified into non-depolarizing (e.g., Tubocurarine, Pancuronium, and Atracurium) and depolarizing agents (e.g., Succinylcholine).
    • Mechanism of action: competitively block cholinergic transmission at the nicotinic receptors by preventing the binding of Ach to its receptor.
    • Route of administration: must be given I.V because oral absorption is poor.

    Succinylcholine

    • Mechanism of action: binds to nicotinic receptors, leading to open Na channels and cause membrane depolarization.
    • Duration of action: 3-6 minutes if given as a single dose.
    • Therapeutic use: used as an adjuvant drug for general anesthesia, to facilitate rapid intubation.
    • Adverse effects: bronchoconstriction and hypotension caused by histamine release, hypotension, arrhythmias, apnea due to respiratory paralysis, and malignant hyperthermia.

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    Description

    This quiz covers the 4th lecture on pharmacology, focusing on nicotinic receptors, their locations, and functions.

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