Pharmacology of Mirabegron and Adrenergic Drugs

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Questions and Answers

What is the mechanism by which amphetamine primarily increases blood pressure?

Inhibition of norepinephrine transporters

Blocking the release of norepinephrine from presynaptic neurons

Direct activation of dopamine receptors

α1 agonist action on the vasculature and β1 stimulation of the heart (correct)

What action does Tyramine have in relation to norepinephrine?

Inhibits the reuptake of norepinephrine

Mediates the synthesis of norepinephrine

Directly stimulates adrenergic receptors

Displaces stored norepinephrine leading to receptor activation (correct)

What is a significant clinical concern when using Mirabegron in hypertensive patients?

It may increase blood pressure (correct)

It enhances the absorption of other drugs

It can lower heart rate significantly

It may decrease glucose metabolism

What is the primary clinical use of pseudoephedrine?

Treatment of nasal and sinus congestion Signup and view all the answers

Which of the following correctly describes the action of phenoxybenzamine?

Nonselective, noncompetitive blocker of α1 and α2 receptors Signup and view all the answers

Which statement about ephedrine is correct?

It raises blood pressure through vasoconstriction and cardiac stimulation Signup and view all the answers

What is a primary mechanism through which coke enhances sympathetic activity?

Blocks the norepinephrine transporter Signup and view all the answers

How do adrenergic antagonists primarily exert their effects?

They bind to adrenoceptors, preventing agonist activation Signup and view all the answers

What is the primary mechanism through which norepinephrine is removed from the synaptic cleft?

Reuptake into the neuron via a transporter Signup and view all the answers

Which adrenergic receptor subtype is primarily involved in smooth muscle constriction?

α1 receptors Signup and view all the answers

What role do α2 presynaptic receptors play in neurotransmitter regulation?

Promote feedback inhibition on norepinephrine release Signup and view all the answers

Which neurotransmitter's release is influenced by the presence of α2 receptors on parasympathetic neurons?

Acetylcholine Signup and view all the answers

Which of the following compounds has a stronger binding affinity for β receptors compared to norepinephrine?

Isoproterenol Signup and view all the answers

Which statement best describes the classification of adrenergic receptors?

They can be divided into α and β receptor categories, with multiple subtypes. Signup and view all the answers

What is the function of serotonin in relation to norepinephrine?

It modulates norepinephrine levels in the synaptic cleft. Signup and view all the answers

In which type of tissue are β2 receptors predominantly found, contributing to high responsiveness to circulating epinephrine?

Skeletal muscle vasculature Signup and view all the answers

Which statement correctly describes the role of noncatecholamines in relation to adrenergic receptors?

They exhibit increased lipid solubility, enhancing central nervous system penetration. Signup and view all the answers

How does epinephrine differ from norepinephrine in terms of receptor activity?

Epinephrine is more potent at β receptors due to a specific substituent on the amine nitrogen. Signup and view all the answers

What type of action do mixed-action adrenergic agonists exhibit?

They enhance norepinephrine release and stimulate adrenoceptors directly. Signup and view all the answers

Which function is NOT associated with the action of epinephrine?

Decreases heart rate and myocardial contractility. Signup and view all the answers

What is the primary effect of epinephrine on glucose metabolism?

It increases glycogenolysis and glucagon release, inducing hyperglycemia. Signup and view all the answers

Which of the following statements regarding direct-acting adrenergic agonists is correct?

They mimic sympathetic stimulation by acting directly on α or β receptors. Signup and view all the answers

What is the significance of the substituent on the amine nitrogen in adrenergic agonists?

It influences the β selectivity of adrenergic agonists. Signup and view all the answers

In which scenario would epinephrine NOT be used effectively?

To reduce heart rate during a myocardial infarction. Signup and view all the answers

Study Notes

Mirabegron and Blood Pressure

Mirabegron can elevate blood pressure; contraindicated in uncontrolled hypertension.
Inhibits CYP2D6 isozyme, potentially enhancing effects of other drugs metabolized by this pathway.

Adrenergic Drugs and Actions

Amphetamine, an indirect-acting adrenergic agent, increases blood pressure via α1 agonism and β1 stimulation.
Tyramine, found in fermented foods, displaces stored norepinephrine, activating adrenoceptors.
Cocaine blocks norepinephrine transporter, increasing sympathetic activity and enhancing actions of epinephrine and norepinephrine.
Ephedrine and pseudoephedrine are mixed-action agents that stimulate α and β receptors while releasing stored norepinephrine.
Ephedrine raises blood pressure through vasoconstriction and cardiac stimulation; used for anesthesia-induced hypotension.
Produces bronchodilation and mild central nervous system (CNS) stimulation.
Pseudoephedrine primarily treats nasal congestion; restrictions exist for its potential methamphetamine production.

Adrenergic Antagonists

Adrenergic antagonists (blockers) bind to adrenoceptors, preventing activation by agonists.
Classified by affinity for α or β receptors; significant in treating cardiovascular diseases.
α-Adrenergic blockers can target α1 or α2 receptors, influencing blood pressure.

Effects of α-Adrenergic Blocking Agents

Blocking α1 receptors decreases peripheral vascular resistance, lowering blood pressure and causing reflex tachycardia.
Phenoxybenzamine is a nonselective blocker for both α receptors, used in treating pheochromocytoma, Raynaud disease, and frostbite.

Noncatecholamines

Noncatecholamines like phenylephrine, ephedrine, and amphetamine have longer half-lives due to the absence of catechol hydroxyl groups.
Increased lipid solubility allows noncatecholamines greater access to the CNS.
The nature of the substituent on amine nitrogen determines β selectivity of adrenergic agonists.

Adrenergic Agonists

Direct-acting agonists interact directly with α or β receptors, replicating sympathetic effects.
Indirect-acting agonists block reuptake or promote norepinephrine release.
Mixed-action agonists enhance norepinephrine release while stimulating adrenoceptors.

Epinephrine Actions

Interacts with both α and β receptors, strengthening myocardial contractility and accelerating heart rate.
Constricts arterioles in skin and viscera; dilates vessels to liver and skeletal muscle.
Facilitates bronchodilation and inhibits allergy mediator release.
Induces hyperglycemia through glycogenolysis and glucagon release; initiates lipolysis via β receptor activation in adipose tissue.
Used in emergencies for bronchospasm and anaphylactic shock, restoring cardiac rhythm in arrest, and prolonging local anesthetic effects.

Norepinephrine and Adrenergic Transmission

Dopamine transforms into norepinephrine, which is stored in vesicles.
Norepinephrine release occurs upon calcium influx triggered by action potentials.
Binds to postsynaptic receptors or presynaptic receptors, influencing intracellular signaling pathways.
Metabolized by catechol-O-methyltransferase (COMT) or recaptured via a sodium-chloride-dependent transporter for reuptake.

Adrenergic Receptor Classification

Adrenergic receptors include α and β receptors, each with subtypes: α1, α2, β1, β2, and β3.
α1 receptors mediate smooth muscle constriction through intracellular signaling; α2 receptors control norepinephrine release, providing feedback inhibition.
β receptors exhibit a higher response to isoproterenol, with specific tissues favoring certain receptor types, such as heart predominating with β1 receptors.

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Description

Explore the effects of Mirabegron on blood pressure and its interactions with other medications. This quiz covers the pharmacological mechanisms of adrenergic drugs like amphetamine and the role of substances like tyramine. Test your knowledge on important drug interactions and cardiovascular effects.