Pharmacology of Adrenergic Agents

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Questions and Answers

What are the different types of adrenergic agents mentioned in the content?

Adrenopositive agents and Adrenonegative agents

Which adrenergic receptor does Epinephrine primarily act on?

α2 adrenoreceptor

α1 adrenoreceptor

β adrenoreceptor (correct)

β2 adrenoreceptor

Norepinephrine, Epinephrine, and Isoprenaline are examples of __________.

Catecholamines

Epinephrine causes bronchodilation.

False Signup and view all the answers

What effect does Isoprenaline have on Mean Blood Pressure (MBP)?

reduces Signup and view all the answers

What effect does Epinephrine have on Systolic Blood Pressure (SBP) in a dose-dependent manner?

Increases Signup and view all the answers

Phenylephrine causes vasoconstriction in nasal mucosa as a ____________ action vasoconstrictor.

local Signup and view all the answers

Selective alpha 2 adrenoreceptor agonists can have a very fast-acting hypotensive effect.

True Signup and view all the answers

Match the following clinical uses with the respective drug:

Acute rhinitis, nose bleeding, paroxysmal ventricular tachycardia

Coronary artery disease, tachycardia, thyrotoxicosis

Glaucoma

Phenylephrine = 1 Propranolol = 2 Timolol = 3 Signup and view all the answers

What is the clinical use of carvedilol?

Chronic heart failure, CAD, hypertension Signup and view all the answers

What is the mechanism of toxicity of beta blockers?

All of the above Signup and view all the answers

Central nervous system toxicity, including convulsions and coma, is commonly seen with beta blockers.

True Signup and view all the answers

Beta blockers may cause ____, hypotension, and bradycardia as cardiac disturbances in poisoning.

first degree heart block Signup and view all the answers

Match the following toxicology treatment with their associated actions:

Atropine = May be ineffective for beta blocker-associated bradycardia Glucagon IV = Administered for bradycardia resistant to basic supportive measures Vasopressors = Often needed to manage shock from beta blocker overdose Signup and view all the answers

Study Notes

Adrenopositive Agents

Adrenopositive agents are also known as adrenomimetic or sympathomimetic agents
Examples include Epinephrine, Isoprenaline, Norepinephrine, and Clonidine
These agents stimulate adrenergic receptors, leading to various physiological effects

Alpha 1 Adrenergic Receptors

Found in smooth muscle, especially in blood vessels, eyes, and urinary bladder
Stimulation leads to:
- Contraction of smooth muscle in blood vessels, eyes, and urinary bladder
- Vasoconstriction, increasing diastolic blood pressure and heart preload
- Mydriasis, increasing intraocular pressure

Alpha 2 Adrenergic Receptors

Found in pancreatic beta cells, nerve endings, and eyes
Stimulation leads to:
- Decreased insulin secretion from pancreatic beta cells
- Decreased norepinephrine release from nerve endings
- Decreased intraocular fluid secretion from eyes

Beta 1 Adrenergic Receptors

Found in heart, kidneys, and adipose tissue
Stimulation leads to:
- Increased heart rate and contractility
- Increased conduction velocity in the heart
- Increased renin release from kidneys
- Lipolysis in adipose tissue

Beta 2 Adrenergic Receptors

Found in smooth muscle, especially in lungs, blood vessels, and uterus
Stimulation leads to:
- Relaxation of smooth muscle in lungs, blood vessels, and uterus
- Bronchodilation, decreasing airway resistance
- Vasodilation, decreasing diastolic blood pressure and heart preload
- Tocolytic effect, inhibiting uterine contractions

Adrenonegative Agents

Adrenonegative agents are also known as adrenergic blockers or sympatholytics
Examples include Propranolol, Doxazosin, and Clonidine
These agents block adrenergic receptors, leading to various physiological effects

Alpha 1 Adrenoreceptor Antagonists

Examples include Doxazosin and Prazosin
Clinical use: treatment of hypertension and symptoms of benign prostatic hyperplasia

Beta Adrenoreceptor Antagonists (BAB)

Examples include Propranolol and Metoprolol
Clinical use: treatment of hypertension, angina pectoris, cardiac arrhythmias, and thyrotoxicosis
Side effects: bradycardia, decreased exercise tolerance, and rebound effect upon sudden withdrawal### Beta Adrenoreceptor Antagonists
Nonselective beta blockers (BAB) may mask initial symptoms of insulin overdose, including tachycardia, tremor, and anxiety.
Cardioselective BAB are safer for patients with diabetes mellitus (DM).

Side Effects and Interactions

Side effects of BAB include bradycardia, AV block, risk of bronchial obstruction, sexual dysfunction, and Raynaud syndrome.
Interactions: Non-selective action may affect the effects of adrenopositive agents.

Nonselective Beta Adrenoreceptor Antagonists

Examples: Timolol eye drops, which reduce intraocular fluid secretion in the ciliary body and decrease intraocular pressure.
Clinical use: Glaucoma.
Target structures in the eye: three muscles (pupil dilator, pupil constrictor muscle, ciliary muscle) and ciliary body epithelium.

Selective Beta 1 Adrenoreceptor Antagonists

Examples: Metoprolol, Bisoprolol, which are highly selective β1 adrenoblockers.
Clinical use: Coronary artery disease (CAD), hypertension, atrial fibrillation, chronic heart failure (CHF), and prophylaxis of migraine attacks.
Lipophilic BAB cause vasoconstriction.
Cardioslectivity β1: less impact on β/vascular smooth muscle, bronchi, uterus, and electrolyte balance (lower risk of hyperkalemia).

Selective Alpha 1, Nonselective Beta Adrenoreceptor Antagonists

Examples: Carvedilol, which has cardiodepressant and antioxidant properties, and reduces peripheral vascular resistance.
Clinical use: Chronic heart failure, CAD, and hypertension.
BAB effect on renin is not clinically important, as it will compensate.

Raynaud Syndrome

Characterized by episodic stenosis of limb arteries and arterioles, usually provoked by cold or stress.
Manifested as sudden paleness or cyanosis of the fingers and toes, including the earlobe and nose.
β2 blockage causes peripheral vasoconstriction, leading to limb freezing.

Beta Adrenoreceptor Antagonist Toxicology

Mechanism of toxicity: All beta blockers antagonize beta1 adrenoreceptors, decreasing heart rate and cardiac contractility.
Nonselective beta blockers also antagonize beta2 receptors, leading to bronchoconstriction, hypoglycemia, and hyperkalemia.

Clinical Presentation

Cardiac disturbances: first-degree heart block, hypotension, and bradycardia.
Central nervous system toxicity: convulsions, coma, and respiratory arrest.
Bronchospasm: most common in patients with preexisting asthma or chronic bronchospastic disease.
Hypoglycemia and hyperkalemia may occur.

Treatment

Emergency and supportive measures: maintain an open airway, assist ventilation, and treat coma, seizures, hypotension, hyperkalemia, and hypoglycemia.
Specific drugs and antidotes: glucagon, calcium chloride, high-dose insulin euglycemic therapy, sodium bicarbonate, and vasopressors.

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Quiz about adrenergic agents, including selective and nonselective agonists, and their effects on the autonomic nervous system.