Isoprenaline in Cardiovascular Treatment

Questions and Answers

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?

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?

Clonidine (correct)

Mirabegron

Ritodrine

Salbutamol

Which of the following drugs is used as a uterine relaxant to suppress premature labor?

Terbutaline Signup and view all the answers

What role do β3 agonists, like mirabegron, play in the genitourinary system?

Relax the detrusor muscle of the bladder. Signup and view all the answers

Which action is performed by non-selective agonists like epinephrine in the treatment of asthma?

They stimulate both bronchial and vascular receptors. Signup and view all the answers

Which β2 agonist is noted to be more effective and less toxic than non-selective options?

Albuterol Signup and view all the answers

How do α2 agonists primarily decrease blood pressure?

By acting via the central nervous system. Signup and view all the answers

What is the primary therapeutic effect of isoprenaline that makes it useful in bradycardia?

Increases cardiac output and heart rate Signup and view all the answers

Which mechanism explains the rebound hyperemia associated with alpha agonist use as nasal decongestants?

Reflex increase in blood flow to the nasal mucosa Signup and view all the answers

Which sympathomimetic is specifically mentioned for inducing mydriasis during retinal examinations?

Phenylephrine Signup and view all the answers

In the treatment of glaucoma, why is dipivefrin considered safer than epinephrine?

It is a prodrug that minimizes systemic exposure to EPI Signup and view all the answers

Which of the following beta agonists is less likely to induce reflex tachycardia when increasing cardiac output?

Beta 2 agonist Signup and view all the answers

What effect do α1 receptor activation have in the context of nasal decongestants?

Decreased volume of nasal mucosa Signup and view all the answers

How do sympathomimetics assist in managing intraocular pressure in glaucoma?

By promoting aqueous humor outflow Signup and view all the answers

Which longer-acting alpha agonists are preferred for nasal decongestion over short-acting ones like phenylephrine?

Xylometazoline and Oxymetazoline Signup and view all the answers

What is the term for transmitter substances released by autonomic nerves in addition to their primary transmitter?

Co-transmitter Signup and view all the answers

Which of the following is NOT a subtype of alpha-1 receptors?

α1C Signup and view all the answers

What is the effect of activating alpha receptors on intracellular calcium levels?

Decreased intracellular calcium levels Signup and view all the answers

Which receptor subtype is found in the heart?

β1 Signup and view all the answers

What is the potency order of catecholamines for alpha receptors?

EPI > NE >> Isoprenaline Signup and view all the answers

What is the effect of beta receptor activation on adenylyl cyclase?

Activation of adenylyl cyclase Signup and view all the answers

Which of the following is NOT a location of beta-2 receptors?

Presynaptic nerve terminals Signup and view all the answers

What is the term for drugs that mimic the actions of norepinephrine (NE) and epinephrine (EPI)?

Sympathomimetics Signup and view all the answers

What happens to the filtration angle during epinephrine administration in angle-closure glaucoma?

It decreases, hindering aqueous humor outflow. Signup and view all the answers

In treating anaphylaxis, which receptors does epinephrine stimulate?

All three receptors: α, β1, and β2. Signup and view all the answers

Which condition is indicated for the use of sympathomimetics as a last resort to elevate blood pressure?

Severe hemorrhage. Signup and view all the answers

What secondary treatments are recommended for anaphylactic shock alongside epinephrine?

Glucocorticoids and antihistamines. Signup and view all the answers

Why is norepinephrine not used for hypotension in most types of shock?

It is ineffective in increasing peripheral resistance. Signup and view all the answers

Which drug is the first choice for oral administration in cases where blood pressure needs enhancement?

Oral ephedrine. Signup and view all the answers

Which condition indicates the use of midodrine over oral ephedrine for enhancing blood pressure?

Chronic hypotension. Signup and view all the answers

What is a consequence of inadequate treatment for hypotension with sympathomimetics?

Increased patient morbidity. Signup and view all the answers

Which of the following drugs primarily acts by inhibiting the reuptake of catecholamines, increasing their concentration in the synaptic cleft?

Cocaine Signup and view all the answers

Which of the following drugs is a non-selective β agonist, meaning it activates all β receptor subtypes?

Isoproterenol Signup and view all the answers

Which of the following drugs is a β3 agonist primarily used for treating bladder overactivity?

Mirabegron Signup and view all the answers

Which of the following drugs has a higher affinity for β2 receptors than β1 receptors?

Epinephrine Signup and view all the answers

Which of the following drugs is a selective α1 agonist with a higher affinity for α1 receptors than α2 or β receptors?

Phenylephrine Signup and view all the answers

Which of the following pairs of drugs both act as non-selective agonists, activating both α and β receptors?

Epinephrine and Norepinephrine Signup and view all the answers

Which of the following statements about α2 agonists is TRUE?

They can decrease blood pressure by inhibiting the release of norepinephrine. Signup and view all the answers

Which of the following drugs is NOT a direct-acting adrenergic agonist?

Tyramine Signup and view all the answers

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.