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Questions and Answers
What is a significant advantage of dopamine over isoproterenol in terms of heart oxygen demand?
What is a significant advantage of dopamine over isoproterenol in terms of heart oxygen demand?
- Dopamine has no effect on oxygen demand.
- Dopamine produces a greater increase in heart rate.
- Dopamine causes less increase in oxygen demand. (correct)
- Dopamine lowers systolic blood pressure.
Which of the following directly contributes to the decrease in total peripheral resistance caused by dopamine?
Which of the following directly contributes to the decrease in total peripheral resistance caused by dopamine?
- Vasodilator effect of dopamine. (correct)
- Elevated blood pressure.
- Increased cardiac output.
- Increased diastolic pressure.
Which drug is useful in treating hypertension and works as an α2 agonist?
Which drug is useful in treating hypertension and works as an α2 agonist?
- Clonidine (correct)
- Mirabegron
- Ritodrine
- Salbutamol
Which of the following drugs is used as a uterine relaxant to suppress premature labor?
Which of the following drugs is used as a uterine relaxant to suppress premature labor?
What role do β3 agonists, like mirabegron, play in the genitourinary system?
What role do β3 agonists, like mirabegron, play in the genitourinary system?
Which action is performed by non-selective agonists like epinephrine in the treatment of asthma?
Which action is performed by non-selective agonists like epinephrine in the treatment of asthma?
Which β2 agonist is noted to be more effective and less toxic than non-selective options?
Which β2 agonist is noted to be more effective and less toxic than non-selective options?
How do α2 agonists primarily decrease blood pressure?
How do α2 agonists primarily decrease blood pressure?
What is the primary therapeutic effect of isoprenaline that makes it useful in bradycardia?
What is the primary therapeutic effect of isoprenaline that makes it useful in bradycardia?
Which mechanism explains the rebound hyperemia associated with alpha agonist use as nasal decongestants?
Which mechanism explains the rebound hyperemia associated with alpha agonist use as nasal decongestants?
Which sympathomimetic is specifically mentioned for inducing mydriasis during retinal examinations?
Which sympathomimetic is specifically mentioned for inducing mydriasis during retinal examinations?
In the treatment of glaucoma, why is dipivefrin considered safer than epinephrine?
In the treatment of glaucoma, why is dipivefrin considered safer than epinephrine?
Which of the following beta agonists is less likely to induce reflex tachycardia when increasing cardiac output?
Which of the following beta agonists is less likely to induce reflex tachycardia when increasing cardiac output?
What effect do α1 receptor activation have in the context of nasal decongestants?
What effect do α1 receptor activation have in the context of nasal decongestants?
How do sympathomimetics assist in managing intraocular pressure in glaucoma?
How do sympathomimetics assist in managing intraocular pressure in glaucoma?
Which longer-acting alpha agonists are preferred for nasal decongestion over short-acting ones like phenylephrine?
Which longer-acting alpha agonists are preferred for nasal decongestion over short-acting ones like phenylephrine?
What is the term for transmitter substances released by autonomic nerves in addition to their primary transmitter?
What is the term for transmitter substances released by autonomic nerves in addition to their primary transmitter?
Which of the following is NOT a subtype of alpha-1 receptors?
Which of the following is NOT a subtype of alpha-1 receptors?
What is the effect of activating alpha receptors on intracellular calcium levels?
What is the effect of activating alpha receptors on intracellular calcium levels?
Which receptor subtype is found in the heart?
Which receptor subtype is found in the heart?
What is the potency order of catecholamines for alpha receptors?
What is the potency order of catecholamines for alpha receptors?
What is the effect of beta receptor activation on adenylyl cyclase?
What is the effect of beta receptor activation on adenylyl cyclase?
Which of the following is NOT a location of beta-2 receptors?
Which of the following is NOT a location of beta-2 receptors?
What is the term for drugs that mimic the actions of norepinephrine (NE) and epinephrine (EPI)?
What is the term for drugs that mimic the actions of norepinephrine (NE) and epinephrine (EPI)?
What happens to the filtration angle during epinephrine administration in angle-closure glaucoma?
What happens to the filtration angle during epinephrine administration in angle-closure glaucoma?
In treating anaphylaxis, which receptors does epinephrine stimulate?
In treating anaphylaxis, which receptors does epinephrine stimulate?
Which condition is indicated for the use of sympathomimetics as a last resort to elevate blood pressure?
Which condition is indicated for the use of sympathomimetics as a last resort to elevate blood pressure?
What secondary treatments are recommended for anaphylactic shock alongside epinephrine?
What secondary treatments are recommended for anaphylactic shock alongside epinephrine?
Why is norepinephrine not used for hypotension in most types of shock?
Why is norepinephrine not used for hypotension in most types of shock?
Which drug is the first choice for oral administration in cases where blood pressure needs enhancement?
Which drug is the first choice for oral administration in cases where blood pressure needs enhancement?
Which condition indicates the use of midodrine over oral ephedrine for enhancing blood pressure?
Which condition indicates the use of midodrine over oral ephedrine for enhancing blood pressure?
What is a consequence of inadequate treatment for hypotension with sympathomimetics?
What is a consequence of inadequate treatment for hypotension with sympathomimetics?
Which of the following drugs primarily acts by inhibiting the reuptake of catecholamines, increasing their concentration in the synaptic cleft?
Which of the following drugs primarily acts by inhibiting the reuptake of catecholamines, increasing their concentration in the synaptic cleft?
Which of the following drugs is a non-selective β agonist, meaning it activates all β receptor subtypes?
Which of the following drugs is a non-selective β agonist, meaning it activates all β receptor subtypes?
Which of the following drugs is a β3 agonist primarily used for treating bladder overactivity?
Which of the following drugs is a β3 agonist primarily used for treating bladder overactivity?
Which of the following drugs has a higher affinity for β2 receptors than β1 receptors?
Which of the following drugs has a higher affinity for β2 receptors than β1 receptors?
Which of the following drugs is a selective α1 agonist with a higher affinity for α1 receptors than α2 or β receptors?
Which of the following drugs is a selective α1 agonist with a higher affinity for α1 receptors than α2 or β receptors?
Which of the following pairs of drugs both act as non-selective agonists, activating both α and β receptors?
Which of the following pairs of drugs both act as non-selective agonists, activating both α and β receptors?
Which of the following statements about α2 agonists is TRUE?
Which of the following statements about α2 agonists is TRUE?
Which of the following drugs is NOT a direct-acting adrenergic agonist?
Which of the following drugs is NOT a direct-acting adrenergic agonist?
Study Notes
Autonomic Nerves and Co-Transmitters
- Most autonomic nerves release co-transmitters alongside their primary transmitter.
- Dopamine is an example of a co-transmitter in adrenergic transmission.
- Catecholamines interact with specialized receptors called adrenergic receptors (adrenoceptors).
Adrenergic Receptor Subtypes
- Adrenoceptors are divided into alpha (α) and beta (β) receptors, rationalized by Raymond Ahlquist in 1948.
- Alpha receptors are further categorized into α1 and α2.
- α1 receptors have three subtypes: α1A, α1B, α1D.
- α2 receptors have three subtypes: α2A, α2B, α2C.
- Beta receptors are segmented into β1, β2, and β3.
Receptor Activation and Mechanisms
- Activation of α receptors decreases intracellular calcium while increasing inositol 1,4,5-triphosphate and diacylglycerol; it inhibits adenylyl cyclase, lowering cyclic AMP (cAMP).
- β receptor activation increases cAMP by stimulating adenylyl cyclase.
Locations of Adrenergic Receptors
- α1 receptors: Found in smooth muscles.
- α2 receptors: Located on presynaptic nerve terminals, platelets, lipocytes, and smooth muscles.
- β1 receptors: Present in the heart, lipocytes, brain, and presynaptic adrenergic/cholinergic terminals.
- β2 receptors: Located in smooth and cardiac muscles.
- β3 receptors: Primarily in lipocytes.
Sympathomimetics
- Drugs that mimic norepinephrine (NE) and epinephrine (EPI) are called sympathomimetics.
- Examples: Isoprenaline activates all β receptor subtypes; α receptor potency is EPI > NE.
Mechanisms of Sympathomimetics
- Some sympathomimetics act directly on adrenergic receptors (e.g., NE, EPI).
- Others act indirectly by displacing stored catecholamines (e.g., amphetamine) or inhibiting reuptake (e.g., tricyclic antidepressants, cocaine).
Examples of Adrenergic Agonists
- α1 agonists: EPI, NE, Phenylephrine, methoxamine, oxymetazoline, metaraminol.
- α2 agonists: Clonidine, oxymetazoline, guanfacine, dexmedetomidine.
- β1 agonists: EPI, NE, isoproterenol, dobutamine.
- β2 agonists: Procaterol, terbutaline, salbutamol, albuterol (short-acting and long-acting).
- β3 agonists: Mirabegron for overactive bladder.
Clinical Uses of Sympathomimetics
- Hypertension: α2 agonists (e.g., clonidine) reduce blood pressure via CNS effects.
- Uterine Relaxation and Overactive Bladder: β2 agonists delay premature labor; β3 agonist mirabegron increases bladder capacity.
- Asthma: β2 agonists (e.g., salbutamol, terbutaline) are effective bronchodilators. Non-selective agonists like isoprenaline can be used but less frequently due to cardiovascular effects.
- Nasal Decongestion: α agonists help reduce nasal mucosa volume, with phenylephrine preferred for nasal sprays.
- Ophthalmic Uses: Phenylephrine induces mydriasis for retinal examination; topical EPI lowers intraocular pressure in glaucoma patients.
- Anaphylaxis: EPI is the primary treatment for anaphylactic shock, acting on all three receptor types (α, β1, β2).
- Hypotension: Sympathomimetics may be used as a last resort to elevate blood pressure in emergencies, with norepinephrine commonly infused for systemic hypotension.
Cautions in Use
- Non-selective agonists can lead to increased heart rate and myocardial oxygen demand.
- EPI should be used cautiously in patients with angle-closure glaucoma due to potential adverse effects.
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Description
This quiz assesses understanding of isoprenaline's effects on the heart, including its use in treating bradycardia and heart block, and its role in asthma treatment. It explores the differences between non-selective beta agonists and beta 2 agonists.
