Pharmacology Lecture 6: Adrenergic Agonists

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Questions and Answers

What is the primary effect of phenylephrine on blood pressure?

It causes hypotension

It raises both systolic and diastolic blood pressures (correct)

It decreases blood pressure

It has no significant effect on blood pressure

Which receptor does oxymetazoline primarily stimulate?

α receptors (correct)

α1 receptors

β2 receptors

β1 receptors

What is a common side effect associated with clonidine?

Increased heart rate

Insomnia

Hypertension

Sedation (correct)

What effect does phenylephrine have on the heart when given parenterally?

Induces reflex bradycardia Signup and view all the answers

What is the primary therapeutic use of albuterol?

Bronchodilation Signup and view all the answers

Which of the following is a side effect of oxymetazoline?

Nervousness Signup and view all the answers

What is a critical consideration when discontinuing clonidine treatment?

It may cause rebound hypertension Signup and view all the answers

How is terbutaline primarily administered for managing asthma symptoms?

Metered-dose inhaler Signup and view all the answers

What is the primary action of indirect-acting adrenergic agonists?

They cause the release of epinephrine or norepinephrine. Signup and view all the answers

Which of the following statements about amphetamine is correct?

Amphetamine can increase blood pressure significantly. Signup and view all the answers

What is a common misconception about the effects of amphetamine?

Amphetamine increases only central nervous system activity. Signup and view all the answers

Why is tyramine significant in pharmacology, even though it is not clinically useful?

It is found in certain fermented foods. Signup and view all the answers

What is NOT a method by which indirect-acting adrenergic agonists operate?

Directly stimulating postsynaptic receptors. Signup and view all the answers

What physiological effect can amphetamine have aside from its central stimulant action?

Increased blood pressure. Signup and view all the answers

Which condition could potentially lead to elevated levels of tyramine?

Consumption of aged cheese. Signup and view all the answers

What characteristic distinguishes indirect-acting adrenergic agonists from direct-acting ones?

They enhance the effects of endogenous neurotransmitters. Signup and view all the answers

What is the primary effect of epinephrine on renal blood flow?

Decreases renal blood flow Signup and view all the answers

What receptor-mediated effect leads to bronchodilation when epinephrine is administered?

β2 action Signup and view all the answers

How does epinephrine influence blood glucose levels?

Increases glycogenolysis and glucagon release Signup and view all the answers

What is a significant therapeutic use of epinephrine?

Short-term relief for bronchospasm Signup and view all the answers

What effect does epinephrine have on diastolic blood pressure?

Significantly decreases diastolic pressure Signup and view all the answers

What is the role of epinephrine in lipolysis?

Stimulates lipolysis via β receptor activity Signup and view all the answers

Which of the following is a reason why selective β2 agonists are preferred for chronic asthma treatment?

They have a longer duration of action Signup and view all the answers

What is a key difference between the actions of epinephrine and albuterol in asthma treatment?

Albuterol is preferred for long-term control Signup and view all the answers

What occurs when a patient taking MAOIs consumes substances normally oxidized by MAO?

Serious vasopressor episodes Signup and view all the answers

How does cocaine uniquely affect norepinephrine in the synaptic space?

It blocks the sodium-chloride dependent transporter Signup and view all the answers

What is a characteristic of ephedrine and pseudoephedrine as mixed-action adrenergic agents?

Directly stimulate both α and β receptors Signup and view all the answers

What effect does ephedrine have on blood pressure?

It raises both systolic and diastolic blood pressure Signup and view all the answers

What is the significance of ephedrine and pseudoephedrine not being catechols?

They are poor substrates for COMT and MAO Signup and view all the answers

What is one of the effects of cocaine on catecholamines in a patient?

Magnified effects from small doses Signup and view all the answers

In terms of pharmacological effects, how do ephedrine and pseudoephedrine compare to epinephrine?

They have similar effects but are less potent Signup and view all the answers

Which action is a characteristic of cocaine's pharmacological properties?

It enhances sympathetic nervous system activity Signup and view all the answers

What is a common side effect of terbutaline when used as a uterine relaxant?

Tremor Signup and view all the answers

Which condition is a contraindication for the use of mirabegron?

Uncontrolled hypertension Signup and view all the answers

What is a characteristic of long-acting β agonists (LABAs) like salmeterol and formoterol?

They are highly efficacious in combination with corticosteroids. Signup and view all the answers

What cardiovascular effects are increased by concurrent use of monoamine oxidase inhibitors (MAOIs)?

Arrhythmias Signup and view all the answers

What is a potential result of administering adrenergic agents orally?

Tachycardia Signup and view all the answers

How long does a single dose of LABAs like salmeterol or formoterol provide bronchodilation?

12 hours Signup and view all the answers

Study Notes

Epinephrine Effects

Constricts arterioles in skin, mucous membranes, and viscera (α receptor effects).
Dilates vessels to liver and skeletal muscle (β2 receptor effects), increasing systolic blood pressure.
Decreases renal blood flow, leading to a slight decrease in diastolic pressure.
Induces bronchodilation via β2 receptors; inhibits histamine release from mast cells.
Causes hyperglycemia by increasing glycogenolysis and glucagon release, while decreasing insulin release.
Initiates lipolysis through β receptor activation in adipose tissue.

Therapeutic Uses of Epinephrine

First-line drug for bronchospasm during acute asthma and anaphylactic shock; respiratory function improves within minutes post-subcutaneous administration.
Selective β2 agonists like albuterol preferred for chronic asthma due to longer action and less cardiac stimulation.

Oxymetazoline

Stimulates α receptors on blood vessels in nasal mucosa and conjunctiva, causing vasoconstriction and reducing congestion.
Can cause side effects such as nervousness, headaches, and sleep disturbances regardless of administration route.

Phenylephrine

Direct-acting synthetic adrenergic that primarily targets α1 receptors; acts as a vasoconstrictor.
Raises both systolic and diastolic blood pressure; induces reflex bradycardia when parenterally administered.
Utilized for hypotension in hospitalized patients, can cause hypertensive headaches and cardiac irregularities.
Serves as a nasal decongestant via topical or oral applications.

Clonidine

An α2 agonist used primarily for hypertension and to alleviate withdrawal symptoms from opioids, tobacco, and benzodiazepines.
Acts centrally on presynaptic α2 receptors, decreasing sympathetic output.
Common side effects include lethargy, sedation, constipation, and xerostomia; abrupt cessation can lead to rebound hypertension.

Albuterol and Terbutaline

Short-acting β2 agonists used mainly as bronchodilators administered via metered-dose inhalers.
Albuterol is preferred for acute asthma management; terbutaline may suppress premature labor.
Side effects include tremors and potential tachycardia or arrhythmias when taken orally, especially in patients with heart conditions.

Salmeterol and Formoterol

Long-acting β agonists (LABAs) specific for β2 receptors; offer sustained bronchodilation over 12 hours.
Not recommended as monotherapy; effective when combined with corticosteroids.

Mirabegron

A β3 agonist that relaxes detrusor smooth muscle, increasing bladder capacity.
Intended for patients with overactive bladder; may elevate blood pressure and contraindicated in uncontrolled hypertension.

Indirect-Acting Adrenergic Agonists

Cause the release, inhibit reuptake, or prevent the degradation of epinephrine or norepinephrine, enhancing their effects without directly acting on postsynaptic receptors.

Amphetamine

Exhibits strong central stimulant actions but also raises blood pressure via α1 agonist and β1 stimulatory effects.

Tyramine

Found in fermented foods; a by-product of tyrosine metabolism.
Not clinically utilized but can cause significant vasopressor episodes in patients on MAOIs.

Cocaine

Unique anesthetic that blocks norepinephrine uptake, enhancing sympathetic activity.
Results in prolonged catecholamine effects and elevated blood pressure via α1 and β receptor activation.

Mixed-Action Adrenergic Agonists

Ephedrine and pseudoephedrine release stored norepinephrine and directly stimulate α and β receptors, leading to similar but less potent effects as epinephrine.
Not catechols; resistant to COMT and MAO degradation, resulting in prolonged action.
Effective for treating hypotension and induce bronchodilation, albeit slower and less potent than epinephrine.

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Description

Dive into the mechanisms of adrenergic agonists with a focus on epinephrine's impact on blood vessels and blood pressure. This quiz will help reinforce key concepts presented in Lecture 6, led by Dr. Salem Abukres. Test your understanding of α and β receptor effects in pharmacology.