Podcast
Questions and Answers
Which of the following is a primary mechanism by which catecholamines like norepinephrine are removed from the synaptic cleft to terminate their action?
Which of the following is a primary mechanism by which catecholamines like norepinephrine are removed from the synaptic cleft to terminate their action?
- Hydrolysis by acetylcholinesterase
- Re-uptake into the presynaptic neuron (correct)
- Diffusion away from the synapse
- Metabolism by butyrylcholinesterase
What is the expected effect of a drug that stimulates alpha-1 adrenergic receptors?
What is the expected effect of a drug that stimulates alpha-1 adrenergic receptors?
- Bronchodilation
- Vasoconstriction (correct)
- Increased heart rate
- Decreased digestion
Which autonomic nervous system primarily uses acetylcholine as its neurotransmitter?
Which autonomic nervous system primarily uses acetylcholine as its neurotransmitter?
- Central nervous system
- Somatic nervous system
- Sympathetic nervous system
- Parasympathetic nervous system (correct)
What is the expected outcome of beta-2 adrenergic receptor activation in the lungs?
What is the expected outcome of beta-2 adrenergic receptor activation in the lungs?
What effect would an alpha-2 adrenergic agonist have on norepinephrine release?
What effect would an alpha-2 adrenergic agonist have on norepinephrine release?
Which of the following is NOT a typical response associated with sympathetic nervous system activation?
Which of the following is NOT a typical response associated with sympathetic nervous system activation?
A drug that mimics the effects of sympathetic stimulation is classified as what type of agent?
A drug that mimics the effects of sympathetic stimulation is classified as what type of agent?
After administering epinephrine to a patient, which of the following effects is primarily mediated by its action on beta-1 adrenergic receptors?
After administering epinephrine to a patient, which of the following effects is primarily mediated by its action on beta-1 adrenergic receptors?
In the context of adrenergic drug mechanisms, what characterizes a 'direct' acting sympathomimetic?
In the context of adrenergic drug mechanisms, what characterizes a 'direct' acting sympathomimetic?
What therapeutic benefit is expected from the administration of mirabegron, a beta-3 adrenergic agonist?
What therapeutic benefit is expected from the administration of mirabegron, a beta-3 adrenergic agonist?
How does epinephrine help in the case of anaphylactic shock?
How does epinephrine help in the case of anaphylactic shock?
In what clinical scenario is the use of norepinephrine as a vasoconstrictor primarily indicated?
In what clinical scenario is the use of norepinephrine as a vasoconstrictor primarily indicated?
Why is epinephrine administered intramuscularly or subcutaneously rather than orally?
Why is epinephrine administered intramuscularly or subcutaneously rather than orally?
Activation of which receptor is likely to cause increased renin secretion from the kidneys?
Activation of which receptor is likely to cause increased renin secretion from the kidneys?
Which of following is the primary effect of activating beta-3 adrenergic receptors?
Which of following is the primary effect of activating beta-3 adrenergic receptors?
What physiological change is associated with the activation of alpha-1 adrenergic receptors in the eye?
What physiological change is associated with the activation of alpha-1 adrenergic receptors in the eye?
Which type of adrenergic receptor is primarily responsible for causing smooth muscle relaxation in the walls of the gastrointestinal tract and urinary bladder?
Which type of adrenergic receptor is primarily responsible for causing smooth muscle relaxation in the walls of the gastrointestinal tract and urinary bladder?
What is a significant contraindication for the use of epinephrine, particularly concerning the cardiovascular system?
What is a significant contraindication for the use of epinephrine, particularly concerning the cardiovascular system?
Xylometazoline is a decongestant that works by stimulating alpha adrenergic receptors in the nasal mucosa. Which adrenergic receptor subtypes does it primarily target?
Xylometazoline is a decongestant that works by stimulating alpha adrenergic receptors in the nasal mucosa. Which adrenergic receptor subtypes does it primarily target?
A patient with which pre-existing condition should be monitored closely if prescribed a beta-2 adrenergic agonist?
A patient with which pre-existing condition should be monitored closely if prescribed a beta-2 adrenergic agonist?
Prazosin is an alpha-1 adrenergic antagonist. What therapeutic effect would be expected from its use?
Prazosin is an alpha-1 adrenergic antagonist. What therapeutic effect would be expected from its use?
What distinguishes norepinephrine from epinephrine in terms of receptor activation?
What distinguishes norepinephrine from epinephrine in terms of receptor activation?
Which mechanism primarily explains why epinephrine can precipitate ventricular fibrillation when administered intravenously?
Which mechanism primarily explains why epinephrine can precipitate ventricular fibrillation when administered intravenously?
What is the underlying mechanism of action for indirect-acting sympathomimetics?
What is the underlying mechanism of action for indirect-acting sympathomimetics?
Why is the rapid onset and short duration of action of epinephrine important in the treatment of acute conditions like anaphylaxis?
Why is the rapid onset and short duration of action of epinephrine important in the treatment of acute conditions like anaphylaxis?
Which effect of epinephrine would most directly contribute to resolving a patient's breathing difficulty during an anaphylactic reaction?
Which effect of epinephrine would most directly contribute to resolving a patient's breathing difficulty during an anaphylactic reaction?
In a patient experiencing cardiogenic shock, which adrenergic receptor is most important to stimulate to increase myocardial contractility and cardiac output?
In a patient experiencing cardiogenic shock, which adrenergic receptor is most important to stimulate to increase myocardial contractility and cardiac output?
What potential adverse effect is most concerning when administering epinephrine to an elderly patient with a history of cardiovascular disease?
What potential adverse effect is most concerning when administering epinephrine to an elderly patient with a history of cardiovascular disease?
Which drug is used to increase blood pressure in acute hypotensive states, and can only be given by slow intravenous infusion?
Which drug is used to increase blood pressure in acute hypotensive states, and can only be given by slow intravenous infusion?
Which receptor does Dobutamine activate?
Which receptor does Dobutamine activate?
Which of the following is a therapeutic use of adrenaline?
Which of the following is a therapeutic use of adrenaline?
A patient is administered a drug that selectively activates beta-2 adrenergic receptors. Which of the following physiological responses would be most anticipated?
A patient is administered a drug that selectively activates beta-2 adrenergic receptors. Which of the following physiological responses would be most anticipated?
A researcher is investigating a new drug that shows promise as a nasal decongestant. If the drug's mechanism of action involves activation of adrenergic receptors in the nasal mucosa, which receptor subtype would be the most appropriate target?
A researcher is investigating a new drug that shows promise as a nasal decongestant. If the drug's mechanism of action involves activation of adrenergic receptors in the nasal mucosa, which receptor subtype would be the most appropriate target?
A patient with pre-existing hypertension is prescribed a non-selective beta-adrenergic agonist for the treatment of severe asthma. Which potential adverse effect is most important to monitor in this patient?
A patient with pre-existing hypertension is prescribed a non-selective beta-adrenergic agonist for the treatment of severe asthma. Which potential adverse effect is most important to monitor in this patient?
A patient is admitted to the emergency room experiencing an acute asthma exacerbation. Which of the following adrenergic agonists, administered via inhalation, would be most appropriate for rapid relief of bronchoconstriction?
A patient is admitted to the emergency room experiencing an acute asthma exacerbation. Which of the following adrenergic agonists, administered via inhalation, would be most appropriate for rapid relief of bronchoconstriction?
An anesthesiologist is preparing to administer a local anesthetic with epinephrine. What is the primary rationale for including epinephrine in the local anesthetic solution?
An anesthesiologist is preparing to administer a local anesthetic with epinephrine. What is the primary rationale for including epinephrine in the local anesthetic solution?
A patient with a known history of benign prostatic hyperplasia (BPH) is prescribed an alpha-1 adrenergic agonist to treat hypotension. Which potential adverse effect should the patient be counseled to monitor for?
A patient with a known history of benign prostatic hyperplasia (BPH) is prescribed an alpha-1 adrenergic agonist to treat hypotension. Which potential adverse effect should the patient be counseled to monitor for?
A cardiac electrophysiologist is considering using isoproterenol during an electrophysiology study. What is the primary rationale for using this agent in this setting?
A cardiac electrophysiologist is considering using isoproterenol during an electrophysiology study. What is the primary rationale for using this agent in this setting?
A researcher is studying the effects of a novel compound on smooth muscle contraction in vitro. The compound increases intracellular calcium levels and causes contraction. Which adrenergic receptor subtype is most likely involved in this effect?
A researcher is studying the effects of a novel compound on smooth muscle contraction in vitro. The compound increases intracellular calcium levels and causes contraction. Which adrenergic receptor subtype is most likely involved in this effect?
During a surgical procedure, a patient develops severe hypotension. The anesthesiologist administers a low dose of epinephrine ($0.1 \mu g/kg$) intravenously. Surprisingly, the patient's blood pressure initially drops further before rising. What best explains this biphasic response?
During a surgical procedure, a patient develops severe hypotension. The anesthesiologist administers a low dose of epinephrine ($0.1 \mu g/kg$) intravenously. Surprisingly, the patient's blood pressure initially drops further before rising. What best explains this biphasic response?
Consider a hypothetical situation where scientists have genetically engineered humans to express functional alpha-2 adrenergic receptors on skeletal muscle fibers. How would administration of a selective alpha-2 agonist most likely affect these individuals?
Consider a hypothetical situation where scientists have genetically engineered humans to express functional alpha-2 adrenergic receptors on skeletal muscle fibers. How would administration of a selective alpha-2 agonist most likely affect these individuals?
Flashcards
Autonomic Nervous System
Autonomic Nervous System
Controls involuntary body activities
Sympathetic Nervous System
Sympathetic Nervous System
This system prepares the body for 'fight or flight'
Sympathetic Neurotransmitters
Sympathetic Neurotransmitters
Catecholamines neurotransmitters include epinephrine and norepinephrine
Parasympathetic Nervous System
Parasympathetic Nervous System
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Acetylcholine
Acetylcholine
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Adrenergic Receptors
Adrenergic Receptors
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Alpha-1 Receptors
Alpha-1 Receptors
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Alpha-2 Receptors
Alpha-2 Receptors
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Beta-1 Receptors
Beta-1 Receptors
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Beta-2 Receptors
Beta-2 Receptors
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Beta-3 Receptor
Beta-3 Receptor
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Sympathomimetics
Sympathomimetics
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Direct-Acting Sympathomimetic
Direct-Acting Sympathomimetic
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Indirect-Acting Sympathomimetic
Indirect-Acting Sympathomimetic
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Adrenaline (Epinephrine)
Adrenaline (Epinephrine)
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Sympatholytics
Sympatholytics
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Epinephrine Administration
Epinephrine Administration
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Anaphylactic shock
Anaphylactic shock
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Angioedema
Angioedema
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Septic shock treatments
Septic shock treatments
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Noradrenaline
Noradrenaline
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Noradrenaline Use
Noradrenaline Use
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Study Notes
- Adrenergic drugs are also known as sympathomimetics.
Case Scenario
- A 6-year-old with a bee sting developed edema with breathing difficulty.
- Paramedics gave epinephrine intramuscularly and transported the child to the hospital.
- The hospital administered oxygen and dexamethasone intravenously.
- The child had a prior allergic reaction to a bee sting that didn't require hospitalization.
- The edema subsided, and the child was discharged.
Autonomic Nervous System
- Controls involuntary body activities.
- Sympathetic response is associated with stress, fight or flight.
- Parasympathetic response is associated with peace, rest, and digest.
- Neurotransmitters for the sympathetic nervous system are catecholamines like epinephrine and norepinephrine.
- The neurotransmitter for the parasympathetic nervous system is acetylcholine.
Sympathetic Nervous System
- Postganglionic neurotransmitter is norepinephrine (NE).
- Adrenergic receptors mediate effects like mydriasis, decreased salivation, bronchodilation, tachycardia, decreased digestion, and decreased urination.
Catecholamines
- Action termination involves re-uptake (80%) and metabolism (20%).
- Re-uptake includes neuronal and granular uptake.
- Metabolism includes monoamine oxidase (MAO) and catechol-O-methyl transferase (COMT).
Adrenergic Receptors
- Includes alpha (α) and beta (β) receptors.
- Alpha receptors include subtypes Alpha-1 (α₁) and Alpha-2 (α₂).
- Beta receptors include subtypes Beta-1 (β₁), Beta-2 (β₂), and Beta-3 (β₃).
Alpha1 Receptors (α₁)
- Gq coupled receptors increase calcium release
- Results in pupillary dilation, smooth muscle contraction
- Causes vasoconstriction, pyloric sphincter contraction, and urinary sphincter contraction.
Alpha2 Receptors (α₂)
- Gi coupled receptors decrease cAMP levels and are inhibitory.
- Norepinephrine binds to alpha2 receptors, decreasing further norepinephrine release, resulting in negative feedback.
Beta1 Receptors (β₁)
- Gs coupled receptors increase cAMP.
- Increase heart rate and contractility.
- Stimulate renin release.
Beta2 Receptors (β₂)
- Gs coupled receptors increase cAMP and cause smooth muscle relaxation.
- Cause bronchodilation, vasodilation, gluconeogenesis, and glycogenolysis.
- Decrease peristalsis/digestion and cause increased urination.
Beta3 Receptors (β₃)
- Gs coupled receptors increase cAMP.
- Found in smooth muscle of the urinary bladder which mediates detrusor muscle relaxation and improves filling capacity.
- Involved in the regulation of lipolysis and thermogenesis.
Receptor Sites and Functions
- α₁ receptors cause vasoconstriction of most blood vessels and contraction of sphincters, but relaxation of GI and UB walls.
- α₂ receptors inhibit norepinephrine (NA) release, reduce sympathetic outflow, and relax GI and UB walls.
- β₁ receptors increase cardiac properties and renin release in the kidney.
- β₂ receptors cause vasodilation, bronchodilation, relaxation of GI/UB walls, and increase liver glycogenolysis and aqueous humor.
Adrenergic Drugs
- Sympathomimetics produce effects like (mimic) sympathetic stimulation.
- Sympatholytics have the opposite effects of sympathetic stimulation.
Classification of Sympathomimetics
- Direct-acting: act directly on receptors.
- Mixed-acting: have both direct and indirect actions.
- Indirect-acting: act by releasing or inhibiting the reuptake of norepinephrine.
Sympathomimetics Classified by Mechanism of Action
- Nonselective direct sympathomimetics: adrenaline (α & β), noradrenaline (α & β1), dopamine (D1, β1, α1), xylometazoline (α1, α2), isoprenaline (β).
- Selective direct sympathomimetics: dobutamine (β₁), salbutamol (β₂), mirabegron (β₃), phenylephrine (α₁), clonidine (α₂), fenoldopam (D1).
- Mixed sympathomimetics: ephedrine (α & β) causes release of noradrenaline.
- Indirect sympathomimetics: amphetamine, cocaine, selegiline, and entacapone
Adrenaline (Epinephrine)
- Chemistry: a catecholamine; unstable in alkaline solutions.
- Pharmacokinetics: poorly absorbed orally (ineffective); given parenterally.
- Short duration of action and does not cross the blood-brain barrier.
- Metabolism: inactivated in the liver by MAO and COMT.
- Excretion: in the urine (7 metabolites).
Epinephrine - Routes of Administration
- Subcutaneous or intramuscular injection into the anterolateral aspect of the thigh.
- Via nebulizer for inhalation.
- Intravenous route is dangerous and used in resuscitation.
- Dosage forms: injectable solutions, prefilled auto-injectors, prefilled syringes.
Epinephrine - Therapeutic Uses
- Acute anaphylactic shock
- It is the life-saving drug
- Administer 0.5 ml (1:1000) intramuscularly, can be repeated
- Causes bronchodilation, increases blood pressure, and decreases histamine release.
- considered a physiological antagonist
- Other drugs can be given: corticosteroids & antihistamine
- Cardiac Arrest: in I.C.U during cardiopulmonary resuscitation (CPR)
- Post-intubation & infectious Croup (Epinephrine Inhalation).
- Acute asthma attack: only for cases associated with anaphylaxis or angioedema, or away from a medical facility with life-threatening symptoms.
Epinephrine - Pharmacodynamics
- Activates all α and β adrenergic receptors.
- Cardiovascular system
- Increases heart rate (+ve chronotropic) and contractility (+ve inotropic) (β₁), increasing cardiac output.
- Causes vasodilation of skeletal muscle blood vessels (β₂).
- Respiratory system
- Relaxation of bronchial smooth muscle (β2).
- Decrease bronchial secretion(a1).
- Metabolic Effect
- Hyperglycemia (↑glucose)Stimulates hepatic glycogenolysis (β2).
- ↑renin secretion (Kidney) (β1)
- Lipolysis: ↑ free fatty acids in blood (ẞ3).
Epinephrine - Effects
- Blood pressure increases.
- Bronchial smooth muscle relaxation (β2).
- Myadriasis due to contraction of dilator pupillae muscle (a1).
- GIT/urinary: wall relaxation (β2), sphincter contraction (a1).
- Elevated renin secretion.
- Increased lipolysis.
Epinephrine - Side Effects
- Cerebral hemorrhage with marked increase in blood pressure.
- Anginal pain due to increased cardiac work.
- Cardiac arrhythmia.
- Acute pulmonary edema.
Epinephrine - Contraindications
- Hypertension
- Ischemic heart disease (IHD)
- Cardiac arrhythmia or with digitalis
- Cardiac outflow obstruction (aortic stenosis, HOCM): contraction against a narrow outlet leads to acute heart failure.
- Thyrotoxicosis where patient has sympathetic over-activity due to increased sensitivity of ẞ receptors.
Noradrenaline (Norepinephrine)
- A natural catecholamine with pharmacokinetics like adrenaline.
- Activates all α (mainly) and β1 receptors with little activity on β2-receptors.
- Increases both systolic & diastolic blood pressure.
- Used as a vasoconstrictor in acute hypotensive states (e.g., septic shock).
- Given by slow intravenous infusion.
Questions and Answers
- Q1: Which of the following is a therapeutic use of noradrenaline?
- A: Acute hypotensive state.
- Q2: Dobutamine activates which of the following receptor(s)?
- B: β1 receptor.
- Q3: Which of the following is a therapeutic use of adrenaline?
- B: Acute Anaphylactic shock.
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