Pharmacy 4A: Functional Antagonism in Pharmacology

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Questions and Answers

What is the antidote for organophosphate poisoning?

Echothiophate

Pralidoxime (correct)

Edrophonium

Botulinum toxin

Which of the following drugs is an irreversible indirect cholinergic agonist?

Bethanechol

Carbachol

Echothiophate (correct)

Rivastigmine

Which of the following drugs acts as a reversible indirect cholinergic agonist?

Bethanechol

Rivastigmine (correct)

Carbachol

Echothiophate

Which of the following drugs binds covalently at the active site?

Echothiophate Signup and view all the answers

Which of the following drugs inhibits the synthesis of acetylcholine?

Hemicholinium Signup and view all the answers

Which of the following best describes the role of mast cells in the body?

First responders to detected threats like allergies and stress Signup and view all the answers

What is the primary activation pathway for H1 histamine receptors?

Activation of Phospholipase C Signup and view all the answers

Which of the following effects is NOT associated with H1 histamine stimulation?

Gastric acid secretion Signup and view all the answers

Which of the following substances is classified as an autacoid?

Serotonin Signup and view all the answers

What happens when histamine is released excessively in response to a threat?

Development of hives Signup and view all the answers

Which receptor type mediates the undesirable peripheral effects of histamine?

H1 receptors Signup and view all the answers

What effect does H2 histamine receptor stimulation primarily have on the body?

Promotion of gastric acid secretion Signup and view all the answers

Which mechanism of action is associated with histamine's effect on H2 receptors?

Activation of Adenylyl cyclase Signup and view all the answers

What neurotransmitter is released from post-ganglionic neurons in the sympathetic nervous system?

Norepinephrine Signup and view all the answers

Which receptor type is primarily activated by acetylcholine in the ganglia of the sympathetic nervous system?

Nicotinic receptor Signup and view all the answers

What effect does the parasympathetic nervous system have on pupil size?

Constriction Signup and view all the answers

Which of the following is a function of the sympathetic nervous system?

Increases heart rate Signup and view all the answers

What primary effect does norepinephrine have on blood pressure?

Increases blood pressure Signup and view all the answers

Which neurotransmitter is secreted by the adrenal medulla during a sympathetic response?

Epinephrine Signup and view all the answers

What is the primary role of the baroreceptor reflex?

Maintain blood pressure Signup and view all the answers

Which system is primarily involved in the 'rest and digest' response?

Parasympathetic nervous system Signup and view all the answers

What role does acetylcholine play in the sympathetic nervous system?

Pre-ganglionic neurotransmitter Signup and view all the answers

In which part of the nervous system does vasoconstriction primarily occur?

Sympathetic nervous system Signup and view all the answers

Which type of signaling involves neurotransmitters communicating between nerve cells and effector organs?

Synaptic signaling Signup and view all the answers

What is the primary function of vesicles in relation to acetylcholine?

To store acetylcholine and prevent degradation Signup and view all the answers

Which of the following neurotransmitters is NOT secreted by pre-ganglionic neurons?

Epinephrine Signup and view all the answers

What effect does the contraction of the ciliary muscle have?

Accommodates for near vision Signup and view all the answers

What is a primary effect of H1 receptor activation in the bronchial smooth muscle?

Bronchoconstriction Signup and view all the answers

Which of the following is a therapeutic use of H1 antihistamines?

Managing allergic and inflammatory conditions Signup and view all the answers

What is the mechanism of action of H2 antihistamines?

They inhibit gastric acid secretion Signup and view all the answers

Which of the following statements about 2nd generation H1 antihistamines is incorrect?

They cause more CNS depression than first-generation antihistamines Signup and view all the answers

What is a common adverse drug reaction associated with H1 antihistamines?

Drowsiness Signup and view all the answers

What is a consequence of anaphylactic shock in relation to histamine release?

Swelling and bronchoconstriction Signup and view all the answers

Which statement regarding the pharmacokinetics of H1 antihistamines is true?

Most are metabolized by CYP450 enzymes Signup and view all the answers

What role do H1 receptors play in the immune response?

They promote the production of nasal and bronchial mucus Signup and view all the answers

Which receptor is primarily responsible for reducing systemic blood pressure?

H2 receptors Signup and view all the answers

What effect do 2nd generation H1 antihistamines generally have on the central nervous system?

They are less sedating than 1st generation options Signup and view all the answers

Which of the following conditions could be treated by H1 antihistamines?

Motion sickness Signup and view all the answers

How is epinephrine used in the context of anaphylactic shock?

It vasoconstricts blood vessels and bronchodilates Signup and view all the answers

What symptom is commonly associated with the activation of sensory nerve endings due to H1 receptor stimulation?

Itching Signup and view all the answers

Which mechanism contributes to the observed effects of H2 receptor activation in the stomach?

Stimulation of gastric acid secretion Signup and view all the answers

What is a likely consequence of H1 receptor antagonism?

Decreased mucus production Signup and view all the answers

What is the effect of non-depolarizing neuromuscular blockers on muscle contraction?

They prevent the binding of acetylcholine. Signup and view all the answers

Which of the following is an adverse reaction associated with succinylcholine?

Hyperkalemia Signup and view all the answers

Which receptor type is associated with the action of alpha-1 adrenergic agonists?

Gq Signup and view all the answers

What is the primary mechanism of action for choline esterase inhibitors?

They inhibit the degradation of acetylcholine. Signup and view all the answers

Which of the following is a characteristic of catecholamines?

High potency Signup and view all the answers

In what clinical scenario is succinylcholine particularly useful?

Rapid endotracheal intubation Signup and view all the answers

What distinguishes beta-adrenergic antagonists from alpha-adrenergic antagonists?

They reduce cardiac output. Signup and view all the answers

Which adrenergic receptor is targeted by salbutamol?

Beta-2 Signup and view all the answers

What is a common adverse reaction associated with adrenergic agonists?

Tremors Signup and view all the answers

Which of the following drugs is classified as an indirect adrenergic agonist?

Amphetamine Signup and view all the answers

What is the primary role of phenylephrine as a medication?

Decongestant Signup and view all the answers

Which of the following is NOT a use for beta blockers?

Decongestant agent Signup and view all the answers

Which drug acts as a competitive alpha-2 blocker?

Yohimbine Signup and view all the answers

What is a known adverse reaction of alpha adrenergic antagonists?

Orthostatic hypotension Signup and view all the answers

Study Notes

Autacoids and Histamine

Autacoids are physiologically active substances with localized and brief effects, including histamine, serotonin, and prostaglandins.
Histamine is a neurotransmitter crucial for allergic reactions and inflammatory responses, affecting multiple body systems.

Histamine Receptors

Histamine receptors are G-protein coupled receptors, primarily classified into H1 and H2 subtypes.
H1 receptors activate phospholipase C (Gq pathway), leading to increased inositol trisphosphate (IP3), diacylglycerol (DAG), and calcium.
H2 receptors stimulate adenylyl cyclase (Gs pathway), increasing cyclic AMP (cAMP) levels.

Histamine's Role in Allergic Reactions

Histamine is released from mast cells in response to threats (allergies, stress), causing symptoms like redness, pain, difficulty breathing, and swelling.
Persistent histamine release can result in hives and other allergic conditions.

Histamine Effects on Various Organs

Lungs: Bronchoconstriction can lead to asthma symptoms.
Skin: Causes flushing, swelling, and itchiness due to dilation and increased permeability of capillaries.
Gastrointestinal: Increases gastric acid secretion impacting digestion.

H1 and H2 Antihistamines

H1 antihistamines are used in allergic and inflammatory conditions and prevent symptoms like itching and swelling.
2nd generation H1 antihistamines are more specific to peripheral receptors, resulting in less sedation and CNS depression.
H2 antihistamines inhibit gastric acid secretion to manage ulcers and heartburn.

Pharmacokinetics of Antihistamines

Most H1 antihistamines have an onset of 1-3 hours, with effects lasting up to 24 hours.
Commonly metabolized by CYP450 enzymes, with differing excretion routes (urine for cetirizine, feces for fexofenadine).

Adverse Effects of H1 Antihistamines

Possible side effects include drowsiness, dry mouth, urinary retention, tachycardia, and increased appetite.

Anaphylactic Shock

Excessive histamine release during anaphylaxis leads to vasodilation, low blood pressure, and bronchoconstriction, potentially closing the airway.
Treatment involves epinephrine administration for vasoconstriction and bronchodilation.

Autonomic Nervous System Overview

Comprises sympathetic, parasympathetic, and enteric systems, with distinct functions and neurotransmitter pathways.
Sympathetic system primarily engages in 'fight or flight' responses, while the parasympathetic system governs 'rest and digest' functions.

Chemical Signaling Mechanisms

Endocrine signaling (hormones), direct contact signaling (local mediators), and synaptic signaling (neurotransmitters) are key communication modes in the body.
Examples include insulin (endocrine), histamine (local mediator), and acetylcholine (neurotransmitter).

Cholinergic System in Autonomic Control

Acetylcholine functions in both sympathetic and parasympathetic systems, binding to muscarinic receptors for various physiological effects.
Organophosphate poisoning antagonizes acetylcholine breakdown, requiring antidotes like pralidoxime for reversal.

Assessment Points for Pharmacology

Knowledge of various drugs affecting acetylcholine synthesis and storage is essential for understanding cholinergic dynamics and their therapeutic implications.### Neuromuscular Blockers
Serve as skeletal muscle relaxants, inhibiting muscle contraction.
Non-depolarizing antagonists prevent acetylcholine (ACh) from binding, blocking muscle contraction.
Depolarizing agonists mimic ACh, causing transient muscle contraction followed by relaxation.
Succinylcholine is a key example, useful for rapid intubation during anesthesia.

Adverse Drug Reactions

Common adverse reactions for succinylcholine include hyperthermia, apnea, and hyperkalemia.

Neurotransmitter Storage and Inhibition

VMAT (Vesicular Monoamine Transporter) stores norepinephrine (NE) and dopamine.
Metyrosine, reserpine, bretylium, and guanethidine inhibit the synthesis, storage, and release of NE/dopamine.
Cocaine and tricyclic antidepressants (e.g., amitriptyline) inhibit the reuptake of NE/dopamine.

Cholinesterase Inhibitors

AChE inhibitors can reverse non-depolarizing neuromuscular blockers by increasing ACh availability.

Adrenergic Receptors

All adrenergic receptors are G-coupled proteins.
Alpha receptors (α1, α2) and beta receptors (β1, β2) initiate various physiological responses via different signaling pathways.

Adrenergic Agonists

Classified into direct (epinephrine, norepinephrine), indirect (cocaine, amphetamine), and mixed (ephedrine).
Ephedrine has a longer duration and penetrates the CNS, while phenylephrine and oxymetazoline act as decongestants primarily through α1 receptors.
Salbutamol is a β2 receptor agonist used as a bronchodilator.

Effects of Adrenergic Receptors

α1: Causes vasoconstriction, increased blood pressure, and mydriasis.
α2: Inhibits release of norepinephrine and acetylcholine.
β1: Increases heart rate and myocardial contractility, stimulating renin release.
β2: Promotes bronchodilation and vasodilation, lowers peripheral resistance, and relaxes uterine smooth muscle.

Adverse Reactions of Adrenergic Agonists

Potential side effects include arrhythmias, headaches, hyperactivity, insomnia, nausea, and tremors.

Adrenergic Antagonists

Alpha blockers (e.g., phenoxybenzamine, prazosin) used for treating conditions like pheochromocytoma and hypertension.
Beta blockers (e.g., metoprolol, propranolol) manage hypertension, angina, cardiac arrhythmias, and prevent migraines without causing postural hypotension.

Anesthesia

Anesthesia is the administration of drugs to prevent pain during surgical procedures.
Benzodiazepines are notable for potential side effects such as oral clefts and altered thermoregulation in newborns.

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Description

This quiz focuses on functional antagonism in the context of pharmacology, specifically relating to autacoids and histamine receptors. Students will explore the mechanisms and implications of these physiological substances. Prepare to test your knowledge on crucial concepts in pharmacokinetics and pharmacodynamics.