Adrenergic System And Drugs
Question 1. What Are Sympathomimetics? Classify Them. Describe Pharmacological Actions, Therapeutic Uses, And Side Effects Of Adrenaline.
Or
Classify Sympathomimetic Amines. Describe The Pharmacological Actions And Therapeutic Uses Of Adrenaline.
Or
Classify Sympathomimetic Drugs. Describe The Therapeutic Uses And Adverse Effects Of Adrenaline.
Or
Classify Sympathomimetics Drugs. Write Uses Of Adrenaline.
Answer:
Sympathomimetics are also known as adrenergic drugs. These are drugs with action similar to that of adrenaline or sympathetic stimulation.
Classification Of Sympathomimetics Or Adrenergic Drugs
1. On The Basis of their Mechanism of Action
- Direct-acting sympathomimetics: They act directly as agonists on α and/or β adrenoreceptors, for Example. are adrenaline, noradrenaline, isoprenaline, phenylephrine, methoxamine, xylometazoline, salbutamol, and many more
- Indirect-acting sympathomimetics: They act on adrenergic neurons to release noradrenaline which then acts on the adrenoreceptors, for Example. tyramine and amphetamine
- Mixed-action sympathomimetics: They act directly as well as indirectly, for Example. ephedrine, amphetamine, mephentermine
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2. On the Basis of their Chemical Structure
- Catecholamines: Sympathomimetics with catechol nuclei are called catecholamines, for Example. adrenaline, noradrenaline,
- Non-catecholamines: Sympathomimetics that lack catechol nuclei are called non-catecholamines, for Example, tyramines, ephedrine, amphetamine, phenylephrine, salbutamol, etc.
3. Classification of Adrenergic Drugs Based on Their Therapeutic Uses
- Pressor Agents: Noradrenaline, Phenylephrine, Ephedrine, Dopamine, Methoxamine, Mephentermine.
- Cardiac Stimulants: Adrenaline, Dobutamine, Isoprenaline
- Bronchodilators: Isoprenaline, Salbutamol, Salmeterol, Formoterol, Bambuterol
- Nasal Decongestants: Phenylephrine, Naphazoline, Xylometazoline, Oxymetazoline, Pseudoephedrine
- CNS Stimulants: Amphetamine, Methamphetamine, Dexamphetamine
- Anorectics: Fenflramine, Sibutramine, Dexfenflramine
- Uterine relaxants and vasodilators: Ritodrine, Salbutamol, Isoxsuprine, Terbutaline.
Pharmacological Actions Of Adrenaline
- Heart: Adrenaline is a cardiac stimulant. It increases heart rate, increases myocardial contractility, increases conduction velocity, and increases cardiac output as well as oxygen consumption. It also increases the excitability and can lead to cardiac arrhythmias.
- Blood vessels: It leads to the constriction of blood vessels of the skin and mucous membranes which have α1 receptors. It also leads to the constriction of mesenteric, renal, pulmonary, and splanchnic blood vessels. It dilates blood vessels of skeletal muscles and coronary blood vessels which have β2 effect.
- Blood pressure: Due to its action on α1 receptors in the heart and blood vessels it leads to an initial rise in blood pressure and this is followed by a gradual fall in blood pressure, due to the action on β2 receptors in skeletal muscles which causes vasodilatation.
- Respiratory system: It leads to the rapid relaxation of bronchial smooth muscle due to its action on β2 receptors and has a short duration of action. It also stops the release of inflammatory mediators from mast cells. Due to its vasoconstrictor effect, it reduces secretion and relieves mucosal congestion due to the vasoconstrictor effect produced by α1 receptors.
- Gastrointestinal: Adrenaline causes gut relaxation, decreases motility, and constricts sphincters.
- Eye: Adrenergic drugs cause contraction of radial muscles of the iris thus causing mydriasis. They decrease the aqueous formation and thus decrease intraocular tension.
- CNS: Adrenaline at its therapeutic doses does not cross the blood-brain barrier and so effects on CNS are very less.
- Metabolism: It causes an increase in blood glucose levels by stimulating liver glycogenolysis; reducing the secretion of insulin and by decrease in uptake of glucose by peripheral tissues.
Therapeutic Uses Of Adrenaline
- Anaphylactic shock: Adrenaline acts as a life-saving drug in anaphylactic shock and also in Type I hypersensitivity reaction. It should be given as 0.3 to 0.5 ml of 1:1000 solution and is given IM.
- Allergy: It reverses the manifestations of allergic disorders.
- Adrenaline along with the lignocaine due to its vasoconstrictor effect causes late absorption of local anesthetic and prolongs the duration of local anesthesia.
- Bronchial asthma: Adrenaline acts as a powerful bronchodilator in bronchial asthma. It is very useful during acute attacks. It should be given 0.3 to 0.5 ml of 1:1000 solution SC
- Hemostatic: Adrenaline acts as a local hemostatic for the control of bleeding from tooth extraction and also in various other surgical procedures.
- Cardiac arrest: Adrenaline is used in the treatment of cardiac arrest which happens due to drowning or electrocution. Adrenaline is given IV in 1:10000 concentration with other supportive measures.
- Glaucoma: Adrenaline is used in glaucoma as it shows poor penetration when it is applied locally in the eye, so it should be given as a prodrug.
Side Effects Of Adrenaline
- It leads to tachycardia, palpitation, headache, restlessness, tremor, and a rise in blood pressure.
- It also leads to cerebral hemorrhage and cardiac arrhythmias.
- At high concentrations, it can cause acute pulmonary edema.
- On IV administration it can cause a sudden rise in blood pressure, ventricular tachycardia, anginas, myocardial infarction, and strokes.
- It also leads to hyperglycemia, hyperlactatemia, and hypokalemia.
Question 2. Classify And Mention Uses Of Sympathomimetics.
Answer:
Sympathomimetics mimics the action of adrenaline or sympathetic stimulation.
Classification Of Sympathomimetics Or Adrenergic Drugs
1. On The Basis of their Mechanism of Action
- Direct-acting sympathomimetics: They act directly as agonists on α and/or β adrenoreceptors, for Example. are adrenaline, noradrenaline, isoprenaline, phenylephrine, methoxamine, xylometazoline, salbutamol, and many more
- Indirect-acting sympathomimetics: They act on adrenergic neurons to release noradrenaline which then acts on the adrenoreceptors, for Example. tyramine and amphetamine
- Mixed-action sympathomimetics: They act directly as well as indirectly, for Example. ephedrine, amphetamine, mephentermine
2. On the Basis of their Chemical Structure
- Catecholamines: Sympathomimetics with catechol nuclei are called catecholamines, for Example. adrenaline, noradrenaline,
- Non-catecholamines: Sympathomimetics that lack catechol nuclei are called non-catecholamines, for Example, tyramines, ephedrine, amphetamine, phenylephrine, salbutamol, etc.
3. Classification of Adrenergic Drugs Based on Their Therapeutic Uses
- Pressor Agents: Noradrenaline, Phenylephrine, Ephedrine, Dopamine, Methoxamine, Mephentermine.
- Cardiac Stimulants: Adrenaline, Dobutamine, Isoprenaline
- Bronchodilators: Isoprenaline, Salbutamol, Salmeterol, Formoterol, Bambuterol
- Nasal Decongestants: Phenylephrine, Naphazoline, Xylometazoline, Oxymetazoline, Pseudoephedrine
- CNS Stimulants: Amphetamine, Methamphetamine, Dexamphetamine
- Anorectics: Fenflramine, Sibutramine, Dexfenflramine
- Uterine relaxants and vasodilators: Ritodrine, Salbutamol, Isoxsuprine, Terbutaline.
Pharmacological Actions Of Adrenaline
- Heart: Adrenaline is a cardiac stimulant. It increases heart rate, increases myocardial contractility, increases conduction velocity, and increases cardiac output as well as oxygen consumption. It also increases the excitability and can lead to cardiac arrhythmias.
- Blood vessels: It leads to the constriction of blood vessels of the skin and mucous membranes which have α1 receptors. It also leads to the constriction of mesenteric, renal, pulmonary, and splanchnic blood vessels. It dilates blood vessels of skeletal muscles and coronary blood vessels which have β2 effect.
- Blood pressure: Due to its action on α1 receptors in the heart and blood vessels it leads to an initial rise in blood pressure and this is followed by a gradual fall in blood pressure, due to the action on β2 receptors in skeletal muscles which causes vasodilatation.
- Respiratory system: It leads to the rapid relaxation of bronchial smooth muscle due to its action on β2 receptors and has a short duration of action. It also stops the release of inflammatory mediators from mast cells. Due to its vasoconstrictor effect, it reduces secretion and relieves mucosal congestion due to the vasoconstrictor effect produced by α1 receptors.
- Gastrointestinal: Adrenaline causes gut relaxation, decreases motility, and constricts sphincters.
- Eye: Adrenergic drugs cause contraction of radial muscles of the iris thus causing mydriasis. They decrease the aqueous formation and thus decrease intraocular tension.
- CNS: Adrenaline at its therapeutic doses does not cross the blood-brain barrier and so effects on CNS are very less.
- Metabolism: It causes an increase in blood glucose levels by stimulating liver glycogenolysis; reducing the secretion of insulin and by decrease in uptake of glucose by peripheral tissues.
Therapeutic Uses Of Adrenergic Drugs
- Anaphylactic shock and allergic disorders.
- Hypotensive state: Vasopressor agent can be used.
- Neurogenic or cardiogenic shock: Dopamine or dobutamine is preferred.
- Congestive heart failure: Short-term use in the decompensated state, i.e. dopamine and dobutamine.
- Cardiac arrest: IV adrenaline is used.
- Partial or complete heart block: Ephedrine or isoprenaline can be used.
- Along with local anesthetic adrenaline is used.
- Control of local bleeding: Adrenaline, Phenylephiderine, and ephedrine is used.
- Nasal decongestant in cold rhinitis: Phenylephiderine, xylometazoline, oxymetazoline are used.
- StokesAdam syndrome: IV adrenaline is used
- Bronchial asthma: Beta-2 agonist.
- Mydriatics: Phenylephiderine decreases intraocular tension.
- Obesity: Anorectics like fenfluramine can be used for a short period.
- Uterine relaxant: Isoxsuprine, salbutamol, turbutaline.
- Insulin hypoglycemia: Adrenaline may be used.
- Parkinsonism and hypokinetic children: Amphetamines can be used.
Question 3. Give Description Of Uses Of Adrenaline.
Answer:
The following are the therapeutic uses of adrenaline:
- Anaphylactic shock: Adrenaline acts as a life-saving drug in anaphylactic shock and also in Type I hypersensitivity reaction. It should be given as 0.3 to 0.5 ml of 1:1000 solution and is given IM.
- Allergy: It reverses the manifestations of allergic
disorders. - Adrenaline along with the lignocaine due to its vasoconstrictor effect causes late absorption of local anesthetic and prolongs the duration of local anesthesia.
- Bronchial asthma: Adrenaline acts as a powerful bronchodilator in bronchial asthma. It is very useful during acute attacks. It should be given 0.3 to 0.5 ml of 1:1000 solution SC.
- Hemostatic: Adrenaline acts as a local hemostatic for the control of bleeding from tooth extraction and also in various other surgical procedures.
- Cardiac arrest: Adrenaline is used in the treatment of cardiac arrest which happens due to drowning or electrocution. Adrenaline is given IV in 1:10000 concentration with other supportive measures.
- Glaucoma: Adrenaline is used in glaucoma as it shows poor penetration when it is applied locally in the eye, so it should be given as a prodrug.
Question 4. Describe Vasopressor Drugs.
Or
Write A Short Note On Vasopressor Drugs.
Or
Write Short Note On Vasopressor Agents.
Answer:
Vasopressor agents or drugs are those which increase blood pressure. Vasopressor drugs are Noradrenaline, Phenylephrine, Ephedrine, Methoxamine, Dopamine, and Mephentermine.
- Noradrenaline: This drug is a catecholamine. It acts on α1, α2, and β1 adrenergic receptors i.e. the drug is α1, α2, and β1 agonist. It mainly acts on the system.
The drug has a direct cardiac effect and it leads to the constriction of all the blood vessels. The drug increases systolic, diastolic, and pulse pressure.
It is only administered by IV infusions. It raises blood pressure in hypotensives it can decrease blood flow to the vital organs by widespread vasoconstriction. - Phenylephrine and methoxamine: Both drugs are selective α1 agonists. These drugs are directly acting α1 agonists and lead to vasoconstriction which causes an increase in peripheral vascular resistance and there is increase in blood pressure.
Topically phenylephrine is used as a nasal decongestant and in the eye it produces mydriasis. Methoxamine is occasionally used pressor agent. - Ephedrine: The drug has a direct action on α1, α2, β1, and β2 receptors and it also releases noradrenaline from sympathetic nerve endings.
Due to its action on α1 receptors, it acts as a vasoconstrictor, nasal decongestant, and as mydriatic.
Due to its action on β1 receptors, it acts as a cardiac stimulant, and due to its action on β2 receptors, it acts as a bronchodilator. IV ephedrine is used to treat hypotension because of spinal anesthesia. - Dopamine: The drug is dopaminergic as well as adrenergic, i.e. it is an α1, α2, and β1 agonist. At its moderate doses dopamine produces positive ionotropic but little chronotropic effect on the heart.
Its vasoconstriction effect occurs only at high doses. This increases afterload and reduces blood flow to renal, mesenteric, and other vital organs. It is used in patients with cardiogenic and septic shock and also in patients with severe heart failure along with renal impairment. - Mephentermine: The drug is an α1 agonist and also releases noradrenaline. It directly acts on α1 agonists and leads to vasoconstriction which causes an increase in peripheral vascular resistance and there is an increase in blood pressure.
It also raises cardiac output as well as systolic and diastolic blood pressure. It is used to prevent and treat hypotension due to spinal anesthesia and surgical procedures, shock in myocardial infarction, and other hypotensive states.
Question 5. List At Least Two Drugs From Beta Adrenoceptor Stimulants. Describe Pharmacological Actions And Therapeutic Uses Of These Class Of Drugs.
Answer:
Beta Adrenoceptor Stimulants
- Adrenaline.
- Noradrenaline.
Pharmacological Actions
- Heart:
- Adrenaline: It increases heart rate, the force of contraction, and conduction thus increasing the cardiac output.
- Noradrenaline: It does not increase the heart rate but produces bradycardia due to the reflux mechanism.
- BP:
- Adrenaline: It increases systolic BP and decreases diastolic BP.
- Noradrenaline: It increases systolic and diastolic BP because beta 2 action is very weak.
- Respiration:
- Adrenaline: It is a potent bronchodilator
- Noradrenaline: It does not cause bronchodilatation.
- GIT:
- Adrenaline and noradrenaline cause gut relaxation decrease motility and cause constriction of the sphincter.
- Bladder: It causes muscle relaxation, constriction of the sphincter, and inhibition of micturition.
- Eye: Contraction of the radial muscle of the iris causes mydriasis.
Therapeutic Uses Of Adrenaline
The following are the therapeutic uses of adrenaline:
- Anaphylactic shock: Adrenaline acts as a life-saving drug in anaphylactic shock and also in Type I hypersensitivity reaction. It should be given as 0.3 to 0.5 ml of 1:1000 solution and is given IM.
- Allergy: It reverses the manifestations of allergic disorders.
Adrenaline along with the lignocaine due to its vasoconstrictor effect causes late absorption of local anesthetic and prolongs the duration of local anesthesia. - Bronchial asthma: Adrenaline acts as a powerful bronchodilator in bronchial asthma. It is very useful during acute attacks. It should be given 0.3 to 0.5 ml of 1:1000 solution SC
- Hemostatic: Adrenaline acts as a local hemostatic for the control of bleeding from tooth extraction and also in various other surgical procedures.
- Cardiac arrest: Adrenaline is used in the treatment of cardiac arrest which happens due to drowning or electrocution. Adrenaline is given IV in 1:10000 concentration with other supportive measures.
- Glaucoma: Adrenaline is used in glaucoma as it shows poor penetration when it is applied locally in the eye, so it should be given as a prodrug.
Therapeutic Uses of Noradrenaline
It raises blood pressure in hypotensives.
Question 6. Write Basis Of Use Of Dopamine In Shock.
Or
Explain Why Dopamine Is Used In The Treatment Of Shock.
Answer:
Dopamine is adrenergic alpha and beta 1 but not beta 2 agonist. In IV low-dose dopamine dilates the blood vessel and increases GFR and sodium secretion.
At a normal dose, it increases the cardiac output and systolic blood pressure with little effect on diastolic blood pressure. It cannot penetrate the blood-brain barrier so no CNS effects.
Hence, it is safe in shock. Dopamine can be used in all types of shocks like cardiogenic, septic, and in severe CHF. Its normal dose is 0.2 to 1 mg/min IV.
The dopamine increases blood pressure and causes urine output hence it is used in the shock.
Question 7. Classify Sympathomimetic Drugs. Describe Pharmacological Actions, Therapeutic Uses, Adverse effects, And Contraindications Of Adrenaline.
Or
Classify Sympathomatic Agents. Describe Pharmacological Action, Therapeutic Uses, And Contraindications For Adrenaline
Answer:
Pharmacological Actions Of Adrenaline
- Heart: Adrenaline is a cardiac stimulant. It increases heart rate, increases myocardial contractility, increases conduction velocity, and increases cardiac output as well as oxygen consumption. It also increases the excitability and can lead to cardiac arrhythmias.
- Blood vessels: It leads to the constriction of blood vessels of the skin and mucous membranes which have α1 receptors. It also leads to the constriction of mesenteric, renal, pulmonary, and splanchnic blood vessels. It dilates blood vessels of skeletal muscles and coronary blood vessels which have β2 effect.
- Blood pressure: Due to its action on α1 receptors in the heart and blood vessels it leads to an initial rise in blood pressure and this is followed by a gradual fall in blood pressure, due to the action on β2 receptors in skeletal muscles which causes vasodilatation.
- Respiratory system: It leads to the rapid relaxation of bronchial smooth muscle due to its action on β2 receptors and has a short duration of action. It also stops the release of inflammatory mediators from mast cells. Due to its vasoconstrictor effect, it reduces secretion and relieves mucosal congestion due to the vasoconstrictor effect produced by α1 receptors.
- Gastrointestinal: Adrenaline causes gut relaxation, decreases motility, and constricts sphincters.
- Eye: Adrenergic drugs cause contraction of radial muscles of the iris thus causing mydriasis. They decrease the aqueous formation and thus decrease intraocular tension.
- CNS: Adrenaline at its therapeutic doses does not cross the blood-brain barrier and so effects on CNS are very less.
- Metabolism: It causes an increase in blood glucose levels by stimulating liver glycogenolysis; reducing the secretion of insulin and by decrease in uptake of glucose by peripheral tissues.
Therapeutic Uses Of Adrenergic Drugs
- Anaphylactic shock and allergic disorders.
- Hypotensive state: Vasopressor agent can be used.
- Neurogenic or cardiogenic shock: Dopamine or dobutamine is preferred.
- Congestive heart failure: Short-term use in the decompensated state, i.e. dopamine and dobutamine.
- Cardiac arrest: IV adrenaline is used.
- Partial or complete heart block: Ephedrine or isoprenaline can be used.
- Along with local anesthetic adrenaline is used.
- Control of local bleeding: Adrenaline, Phenylephiderine, and ephedrine is used.
- Nasal decongestant in cold rhinitis: Phenylephiderine, xylometazoline, oxymetazoline are used.
- StokesAdam syndrome: IV adrenaline is used
- Bronchial asthma: Beta-2 agonist.
- Mydriatics: Phenylephiderine decreases intraocular tension.
- Obesity: Anorectics like fenfluramine can be used for a short period.
- Uterine relaxant: Isoxsuprine, salbutamol, turbutaline.
- Insulin hypoglycemia: Adrenaline may be used.
- Parkinsonism and hypokinetic children: Amphetamines can be used.
Adverse Effects Of Adrenaline
- On SC or IM administration it causes transient restlessness palpitation, anxiety, headache, pallor, and tremors.
- On IV administration it causes the following adverse effects, i.e.
- Cerebral hemorrhage
- Sudden rise in blood pressure
- Ventricular tachycardia/fibrillation
- Angina
- Myocardial infarction.
Contraindication
Adrenaline is contraindicated in hypertensive, hyperthyroid, and in angina patients.
Adrenaline mixed with the local anesthetic should be used very cautiously for dental anesthesia in patients with heart disease.
It should not be given during anesthesia with halothane and to patients receiving beta-blockers as cerebral hemorrhage due to its unopposed action on vascular alpha-1 receptors.
Question 8. Write A Short Note On Uses And Adverse Effects Of Adrenaline.
Or
Write In Brief On Uses And Adverse Effects Of Adrenaline.
Answer:
Therapeutic Uses Of Adrenaline
- Anaphylactic shock: Adrenaline acts as a life-saving drug in anaphylactic shock and also in Type I hypersensitivity reaction. It should be given as 0.3 to 0.5 ml of 1:1000 solution and is given IM.
- Allergy: It reverses the manifestations of allergic disorders.
- Adrenaline along with the lignocaine due to its vasoconstrictor effect causes late absorption of local anesthetic and prolongs the duration of local anesthesia.
- Bronchial asthma: Adrenaline acts as a powerful bronchodilator in bronchial asthma. It is very useful during acute attacks. It should be given 0.3 to 0.5 ml of 1:1000 solution SC
- Hemostatic: Adrenaline acts as a local hemostatic for the control of bleeding from tooth extraction and also in various other surgical procedures.
- Cardiac arrest: Adrenaline is used in the treatment of cardiac arrest which happens due to drowning or electrocution. Adrenaline is given IV in 1:10000 concentration with other supportive measures.
- Glaucoma: Adrenaline is used in glaucoma as it shows poor penetration when it is applied locally in the eye, so it should be given as a prodrug.
Adverse Effects Of Adrenaline
- On SC or IM administration it causes transient restlessness palpitation, anxiety, headache, pallor, and tremors.
- On IV administration it causes the following adverse effects, i.e.
- Cerebral hemorrhage
- Sudden rise in blood pressure
- Ventricular tachycardia/fibrillation
- Angina
- Myocardial infarction.
Question 9. Classify Adrenergic Drugs According To Their Therapeutic Uses. How Will You Manage A Patient Of Anaphylactic Shock?
Answer:
Classification Of Adrenergic Drugs Based On Their Therapeutic Uses
- Pressor Agents: Noradrenaline, phenylephrine, ephedrine, dopamine, methoxamine, phentermine
- Cardiac Stimulants: Adrenaline, Dobutamine, Isoprenaline
- Bronchodilators: Isoprenaline, Salbutamol, Salmeterol, Formoterol, Bambuterol
- Nasal Decongestants: Phenylephrine, Naphazoline, Xylometazoline, Oxymetazoline, Pseudoephedrine
- CNS Stimulants: Amphetamine, Methamphetamine, Dexamphetamine
- Anorectics: Fenfluramine, Sibutramine, Dexfenfluramine
- Uterine relaxants and Vasodilators: Ritodrine, Salbutamol, Isoxsuprine, Terbutaline.
Management Of Anaphylactic Shock
- Summon ambulance
- Always check whether respiratory distress is due to other causes
- Assess the degree of cardiovascular collapse by checking pulse and blood pressure
- Assess the degree of airway obstruction
- Stop the administration of the drug
- The patient should be kept supine
- Assess breathing difficulty by checking for stridor, wheezing
- Administer oxygen to the patient with a face mask
- Give antihistamine chlorpheniramine maleate 10 mg
- Administer hydrocortisone 20 mg
- Monitor consciousness, airway, breathing, circulation, pulse, and blood pressure
- Raise legs if blood pressure is low
- Adrenaline 1:1000, 0.5 ml IM is given immediately
- Repeat IM adrenaline every 5 minutes while waiting for the ambulance
- Administer 100% oxygen
- CPR if cardiac arrest occurs
- If the BP fall is rapid, 1:10,000 adrenalin may be infused IV slowly.
Question 10. Write Short Note On Nasal Decongestant.
Answer:
- Nasal decongestants are adrenergic drugs.
- The nasal decongestants are phenylephrine, xylometazoline oxymetazoline, naphazoline, pseudoephedrine, and phenylpropanolamine.
- Nasal decongestants are alpha agonists which on topical application as a dilute solution produce local vasoconstriction and relieve nasal congestion.
- Nasal decongestants are used in allergic rhinitis, common cold, sinusitis, etc.
- If used chronically the nasal decongestants can lead to rebound congestion.
- Topical decongestants produce adverse effects such as atrophic rhinitis, anosmia, and local irritation. If these are absorbed systemically they can cause hypertension.
- Pseudoephedrine as well as phenylephrine are used combined with antihistaminics in anticold formulations.
- The imidazoline compounds, i.e. naphazoline, xylometazoline and oxymetazoline are selective α2 agonist. These have a long duration of action.
- Regular use of nasal decongestants should be avoided because mucosal ciliary function is impaired.
Question 11. Classify Adrenergic Drugs According To Their Therapeutic Uses.
Answer:
Classification of Adrenergic Drugs Based on Their Therapeutic Uses
- Pressor Agents: Noradrenaline, Phenylephrine, Ephedrine, Dopamine, Methoxamine, Mephentermine.
- Cardiac Stimulants: Adrenaline, Dobutamine, Isoprenaline
- Bronchodilators: Isoprenaline, Salbutamol, Salmeterol, Formoterol, Bambuterol
- Nasal Decongestants: Phenylephrine, Naphazoline, Xylometazoline, Oxymetazoline, Pseudoephedrine
- CNS Stimulants: Amphetamine, Methamphetamine, Dexamphetamine
- Anorectics: Fenflramine, Sibutramine, Dexfenflramine
- Uterine relaxants and vasodilators: Ritodrine, Salbutamol, Isoxsuprine, Terbutaline.
Question 12. Classify Sympathomimetics. Write Contraindication And Therapeutic Uses Of Adrenaline. Add A Short Note On the Adrenaline And Lignocaine Combination.
Answer:
Classification Of Sympathomimetics Or Adrenergic Drugs
1. On The Basis of their Mechanism of Action
- Direct-acting sympathomimetics: They act directly as agonists on α and/or β adrenoreceptors, for Example. are adrenaline, noradrenaline, isoprenaline, phenylephrine, methoxamine, xylometazoline, salbutamol, and many more
- Indirect-acting sympathomimetics: They act on adrenergic neurons to release noradrenaline which then acts on the adrenoreceptors, for Example. tyramine and amphetamine
- Mixed-action sympathomimetics: They act directly as well as indirectly, for Example. ephedrine, amphetamine, mephentermine
2. On the Basis of their Chemical Structure
- Catecholamines: Sympathomimetics with catechol nuclei are called catecholamines, for Example. adrenaline, noradrenaline,
- Non-catecholamines: Sympathomimetics that lack catechol nuclei are called non-catecholamines, for Example, tyramines, ephedrine, amphetamine, phenylephrine, salbutamol, etc.
3. Classification of Adrenergic Drugs Based on Their Therapeutic Uses
- Pressor Agents: Noradrenaline, Phenylephrine, Ephedrine, Dopamine, Methoxamine, Mephentermine.
- Cardiac Stimulants: Adrenaline, Dobutamine, Isoprenaline
- Bronchodilators: Isoprenaline, Salbutamol, Salmeterol, Formoterol, Bambuterol
- Nasal Decongestants: Phenylephrine, Naphazoline, Xylometazoline, Oxymetazoline, Pseudoephedrine
- CNS Stimulants: Amphetamine, Methamphetamine, Dexamphetamine
- Anorectics: Fenflramine, Sibutramine, Dexfenflramine
- Uterine relaxants and vasodilators: Ritodrine, Salbutamol, Isoxsuprine, Terbutaline.
Therapeutic Uses Of Adrenaline
- Anaphylactic shock: Adrenaline acts as a life-saving drug in anaphylactic shock and also in Type I hypersensitivity reaction. It should be given as 0.3 to 0.5 ml of 1:1000 solution and is given IM.
- Allergy: It reverses the manifestations of allergic disorders.
- Adrenaline along with the lignocaine due to its vasoconstrictor effect causes late absorption of local anesthetic and prolongs the duration of local anesthesia.
- Bronchial asthma: Adrenaline acts as a powerful bronchodilator in bronchial asthma. It is very useful during acute attacks. It should be given 0.3 to 0.5 ml of 1:1000 solution SC
- Hemostatic: Adrenaline acts as a local hemostatic for the control of bleeding from tooth extraction and also in various other surgical procedures.
- Cardiac arrest: Adrenaline is used in the treatment of cardiac arrest which happens due to drowning or electrocution. Adrenaline is given IV in 1:10000 concentration with other supportive measures.
- Glaucoma: Adrenaline is used in glaucoma as it shows poor penetration when it is applied locally in the eye, so it should be given as a prodrug.
Contraindications Of Adrenaline
- Adrenaline is contraindicated in hypertensive, hyperthyroid, and in angina patients.
- Adrenaline mixed with the local anesthetic should be used very cautiously for dental anesthesia in patients with heart disease.
- It should not be given during anesthesia with halothane.
- Patients receiving beta-blockers can cause hypertensive crisis and cerebral hemorrhage due to their unopposed action on vascular alpha-1 receptors.
Adrenaline And Lignocaine Combination
Adrenaline is added to lignocaine because of the following reasons:
1. Infiltration block: The duration of action of lignocaine is proportional to the time of contact with the nerve.
When lignocaine is infiltrated around the injury site (by subcutaneous route), some of it may enter the subcutaneous blood vessels. It has two implications:
- Lignocaine goes away from the nerves of the injury site. Thus, its action quickly diminishes.
- The lignocaine which has entered the blood vessel may go to the heart and brain causing systemic toxicity, i.e. cardiotoxicity and neurotoxicity.
The addition of adrenaline cause vasoconstriction and thus lignocaine is not able to enter the blood vessels resulting in:
- Prolongation of the duration of action
- Less systemic toxicity
- Adrenaline provides a bloodless field for surgery.
2. Spinal anesthesia: Adrenaline is added to lignocaine for spinal anesthesia to increase the duration and intensity of the block. It acts by:
- Decreasing the spinal blood flow may reduce the clearance of lignocaine from CSF
- Acting on the α2A; receptors, it may reduce the tiring of neurons and inhibit the release of pain mediators like substance P or neurokinin-1.
Question 13. Enumerate Three Indications For The Use Of Adrenaline.
Answer:
Following are the three indications for the use of adrenaline:
- Anaphylactic shock: Adrenaline acts as a life-saving drug in anaphylactic shock and also in Type I hypersensitivity reaction. It should be given as 0.3 to 0.5 ml of 1:1000 solution and is given IM.
- Allergy: It reverses the manifestations of allergic disorders.
- Bronchial asthma: Adrenaline acts as a powerful bronchodilator in bronchial asthma. It is very useful during acute attacks. It should be given 0.3 to 0.5 ml of 1:1000 solution SC.
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