40 Questions
What is the effect of adrenaline on blood vessels at high doses?
Constriction of arterioles in skin, mm, and viscera
What is the primary mechanism of inactivation of catecholamines?
Inactivation by COMT post-synoptically and by MAO in the neuron
Which of the following is NOT a characteristic of catecholamines?
They can penetrate the blood-brain barrier
What is the effect of adrenaline on the cardiovascular system at low doses?
+ve inotropic and +ve chronotropic effect
What is the effect of the fight or flight response on respiration?
Increase in depth and rate of respiration
Which of the following is a characteristic of non-catecholamines?
They are lipophilic and can penetrate the blood-brain barrier
What is the effect of adrenaline on blood pressure?
Increase in systolic blood pressure and decrease in diastolic blood pressure
Which of the following is an example of a direct non-selective agonist?
Adrenaline
What is the effect of the fight or flight response on muscle glycogen?
Increase in muscle glycogen
What is the effect of adrenaline on renal blood flow?
Increase in renal blood flow
What is the effect of epinephrine on glycogenolysis?
Increase hepatic glycogenolysis
What is the main indication for the use of noradrenaline?
Shock
What is the effect of isoprenaline on peripheral resistance?
Decrease peripheral resistance
What is the action of dopamine on D1 receptors?
Vasodilation
What is the side effect of epinephrine on the central nervous system?
Headache, anxiety, and tremor
What is the effect of epinephrine on insulin release?
Decrease insulin release
What is the effect of noradrenaline on heart rate?
Decrease heart rate
What is the effect of isoprenaline on bronchial smooth muscle?
Bronchodilation
What is the side effect of noradrenaline on the cardiovascular system?
Hypertension
What is the action of dopamine on D2 receptors?
Similar to alpha-2 receptor
What is the main mechanism of indirect acting agonists?
They potentiate the endogenous norepinephrine and epinephrine
Which of the following adrenergic agonists is used to control withdrawal symptoms from opiates?
Clonidine
What is the main side effect of clonidine?
Lethargy
Which of the following adrenergic agonists has a slow onset bronchodilator effect?
Ephedrine
What is the mechanism of desensitization of adrenergic receptors?
Sequestration of the receptors
Which of the following adrenergic agonists is used topically as a nasal or oral decongestant?
Phenylephrine
What is the main use of phenylephrine in ophthalmology?
To produce mydriasis
Which of the following adrenergic agonists has a short half-life?
Pseudoephedrine
Which of the following is a side effect of adrenergic agonists?
Tachycardia
Which of the following classes of adrenergic agents has utility in the management of hypertension?
α2 Agonist
Which of the following is NOT an indication for fenoldopam?
Bradycardia
What is the mechanism of action of alpha-1 receptors?
G-protein coupled - PLC - IP3+DAG - Ca++
Which of the following beta-agonists is used in premature labor?
Terbutaline
What is the primary indication for dobutamine?
Acute heart failure
What is the primary side effect of oxymetazoline?
Rebound congestion
What is the mechanism of action of beta-2 agonists?
G-protein coupled - AC - cAMP
What is the primary indication for fenoldopam?
Hypertension
What is the primary side effect of SABA?
All of the above
Which of the following is a long-acting beta-2 agonist?
Salmeterol
What is the primary indication for oxymetazoline?
Nasal congestion
Study Notes
Adrenergic Agonists
- Adrenergic agonists are substances that stimulate the adrenergic receptors in the body, which can lead to a variety of physiological responses.
Synthesis and Release
- Catecholamines are synthesized in the adrenal medulla and nerve endings.
- They are inactivated by COMT post-synaptically and by MAO in the neuron.
- They have a short duration of action.
Actions and Receptors
- Adrenergic receptors are categorized into α, β, and dopamine receptors.
- α receptors are further divided into α1 and α2 receptors.
- β receptors are divided into β1, β2, and β3 receptors.
- Dopamine receptors are divided into D1 and D2 receptors.
Direct Acting Agonists (Non-Selective)
-
Adrenaline (Epinephrine)
- Acts on α and β receptors
- At low doses, it has β effects (vasodilation)
- At high doses, it has α effects (vasoconstriction)
- Indications: anaphylaxis, bronchospasm, cardiac arrest, dental use, epistaxis, and intraocular surgery
- Side effects: CNS (headache, anxiety, tremor), CVS (hypertension, dysrhythmia, angina pectoris), respiratory (pulmonary edema), metabolic (hyperglycemia)
-
Noradrenaline (Norepinephrine)
- Acts on α receptors
- Increases peripheral resistance and systolic blood pressure
- Indications: shock
- Contraindications: peripheral vascular diseases, hypertension, asthma
- Side effects: same as epinephrine, plus sloughing and necrosis at the injection site
-
Isoprenaline
- Synthetic catecholamine
- Non-selective β-1 and β-2 agonist
- Acts on the heart (increases contractility and rate) and respiratory system (bronchodilation)
- Side effects: same as epinephrine
-
Dopamine
- Acts on D1 and D2 dopamine receptors
- Indications: cardiogenic and septic shock, hypotension, oliguria, bradycardia, and severe heart failure
- Side effects: hypertension, dysrhythmias are short-lived
Direct Acting Agonists (Selective)
-
Dobutamine
- Synthetic catecholamine
- β1 agonist
- Increases cardiac contractility and heart rate
- Indications: acute heart failure, cardiac surgery
- Side effects: increases oxygen demand of the myocardium
-
SABA (Short-Acting Beta-2 Agonist)
- Albuterol, metaproterenol, and terbutaline
- β2 agonist
- Bronchodilator (inhaler)
- Terbutaline injection relaxes the uterus, used in premature labor
- Side effects: tremor, restlessness, anxiety, tachycardia (if given orally)
-
LABA (Long-Acting Beta-2 Agonist)
- Salmeterol, indacaterol, and formoterol
- β2 agonist
- Long-acting (12 hours)
- Indications: asthma and COPD
- Used in combination with other asthma medications as inhaled corticosteroids
-
Oxymetazoline
- α1 and α2 agonist
- Ophthalmic and nasal decongestant
- Side effects: irritation, sneezing (nasal administration), headaches, and sleep disturbances
-
Phenylephrine
- Selective α1 agonist
- Vasoconstrictor (increases systolic and diastolic blood pressure)
- Uses: hypotension in patients with rapid heart rate, paroxysmal supraventricular tachycardia, topical decongestant, and ophthalmic solution for mydriasis
- Side effects: large doses cause hypertensive headache and cardiac irregularities
-
Clonidine
- Selective α2 agonist
- Used to treat hypertension by inhibiting sympathetic vasomotor center, decreasing sympathetic outflow
- Used to control withdrawal symptoms from opiates, benzodiazepines, and tobacco
- Side effects: lethargy, sedation, xerostomia
Indirect Acting Agonists
- They potentiate the endogenous nor-epinephrine and epinephrine by increasing release, inhibiting re-uptake, or inhibiting degradation.
- Examples: amphetamine, tyramine, cocaine, and MAO/COMT inhibitors.
Mixed Agonists
- They induce release of nor-epinephrine and activate adrenergic receptors.
- Examples: ephedrine and pseudoephedrine
- They have α1 and β effects, and penetrate the CNS
- Uses: ephedrine is used in hypotension, and pseudoephedrine is used in nasal and sinus congestion.
Adrenergic Agonists Adverse Effects
- Arrhythmias
- Hyperactivity
- Insomnia
- Tremors
- Tachycardia
- Headache
- Nausea
This quiz covers the sympathetic nervous system, including the fight or flight response, synthesis and release, actions and receptors, and effects on the body.
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