Drugs that bind to these receptors and augment the system are called sympathomimetics, while those that bind to these receptors and inhibit or prevent the binding of endogenous ligands are called sympatholytics.

1. SYMPATHOMIMETIC
AGENTS
Adrenergic agents
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PRESENTED BY: Ms. Sapna Rani
ASSISTANT PROFESSOR
PHARMACOLOGY
MMCP, MM(DU)

2. NERVOUS SYSTEM
CENTRALNERVOUS SYSTEM PERIPHERALNERVOUS SYSTEM
AUTONOMIC NERVOUS SYSTEM
SOMATIC
NERVOUS SYSTEM
SYMPATHETIC SYSTEM PARASYMPATHETIC
SYSTEM
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3. Drugs that partially or completely mimic the
actions of norepinephrine (NE) or epinephrine
(Epi).
Definition of
Sympathomimetic drugs

4. SYNTHESI
S
TYROSINE
DOPA
DOPAMINE
NA
ADRENALINE
Tyrosine hydroxylase
DOPA decarbxylase
Dopamine β-
hydroxylase
N-methyltransferase
Phenylalanine
Phenylalanine
hydroxylase

5. Mechanism: Norepinephrine Release
and Recycling

6. Where are the adrenergic
receptors?
Receptor α1 α2 β1 β2 β3
localization Blood
vessel
s
CNS Heart Lungs Adipose
tissue
Prostatic
urethra &
eye α1A
Blood
vessels
Kidney-
juxta
glomerular
cells
Uterus
GIT GIT
Bladder

7. Adrenergic receptors, Subtypes,
agonists and antagonists
Receptors Agonists Antagonists
α1a
Phenylephrine/ Methoxamine Prazosin/terazocine
α1b
Phenylephrine/Methoxamine Prazosin/terazocine
α2a
Oxymetazoline/ Clonidine Yohimbine/ Rauwolscine
α2b
Oxymetazoline/ Clonidine Yohimbine/ Rauwolscine
β1 Dobutamine/ Xamoterol Atenolol, acebutolol
β2 Terbutaline/ Salbutamol
β3 BRL 37344
D1 Fenoldopam
D2 Bromocriptine, Lysoride

8. SYMPATHOMIMETICS
CLASSIFICATION
3 types of classifications
1. based on their chemical groups
2. Mode of action
3. Therapeutic classification
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9. Classification on the basis of their Chemical structure
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Catecholamines:
Sympathomimetics with catechol nucleus are called
catecholamines.
Adrenaline, NA, DA, Isoprenaline, Dobutamine
Non-Catecholamines :
Tyramine, Ephedrine, Amphetamine, Salbutamol
HO
HO
C C N

10. 2. Mode of action
Direct receptor agonists:
alpha agonists 1& 2
beta agonists 1& 2
alpha & beta agonists
Indirectly acting :
reuptake inhibitors
release promoters
metabolism inhibitors
Both direct and indirect:
Ephedrine
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11. THERAPEUTIC CLASSIFICATION OF ADRENERGIC
DRUGS:
I. Vasopressors:
Noradrenaline, Phenylephrine, Ephedrine
II. Cardiac stimulants:
Adrenaline, Dobutamine, Isoprenaline
III. Bronchodilators: ADRENALINE
Isoprenaline,Salbutamol, Terbutaline
IV. Nasal decongestants:
Phenylephrine, Naphazoline, Xylometazoline
V. Anorectics: Fenfluramine, Sibutramine, Dexfenfluramine
VI. Uterine relaxants :
Ritodrine, Salbutamol, Isoxsuprine,Terbutaline
VII: CNS stimulants:
Isoprenaline
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12. ADRENALINE PHARMACOLOGICAL ACTIONS
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13. 1. CARDIOVASCULAR SYSTEM:
Heart:
It is a powerful cardiac stimulant
It interacts with Beta1 receptors.
Increases heart rate
Increases force of contraction
Increases the cardiac output
Increases automaticity and conduction velocity
The cardiac work and oxygen requirement is
markedly increased
Increase in the excitability and tendency to cause
arrhythmias.
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14. Blood vessels of the skin and mucous membranes
predominantly contain alpha1 receptors. It causes
vasoconstriction.
B. BLOOD VESSELS :
Both vasoconstriction (alpha) and vasodilatation
(Beta 2) can occur depending on the drug, its dose
and vascular bed.
Constricts renal, mesenteric, pulmonary and
splanchnic blood vessels.
Dilates the blood vessels of skeletal muscles and
coronaries.
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15. C. Blood Pressure:
Biphasic response with Adrenaline.
The initial rise in BP due to predominant alpha1
action on blood vessels and beta1 actions on
heart.
Followed by fall in BP due to beta2 mediated
vasodilatation in skeletal muscles.
Dales vasomotor reversal:
Administration of Adrenaline after the alpha1
blockade produces a fall in BP.
This is referred as vasomotor reversal.
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16. 2. Respiration :
Adrenaline relaxes bronchial smooth muscle ( Beta2).
It inhibits the release of mediators from mast cells (beta2).
It reduces secretions and relives mucosal congestion by
vasoconstrictor action.
3. Eye :
Poor penetration into cornea.
Hence its administered as pro-drug Dipivefrin
Mydriasis occurs due to contraction of radial muscles of
iris (alphal)
Reduced aqueous formation.
Facilitation of trabecular outflow
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17. 4. GIT:
Relaxation occurs through activation of both alpha and beta
receptors.
Peristalsis is reduced and sphincters are constricted.
5. Bladder:
Trigone contraction (alpha)
Difficulty in urination
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18. Administration and preparations:
orally inactive
EPI administered SC - absorbed slowly
By IM route absorbed -- more rapidly.
IV route - Arrhythmias
Does not cross the BBB
EPI is rapidly inactivated in the body by COMT and MAO.
It appears in the urine as VMA and metanephrine.
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19. Adrenaline Uses: ABCDE
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A: In Anaphylactic shock Injection 0.5 ml 1:1000, I.M.
B: Bronchial Asthma 0.5ml SC 1 in 1000
C: Cardiac arrest IV 1 in 10,000
D: To increase the duration of action of local anaesthetic
along with local anaesthetics 1in 20,000- 1,00,000
E: Epistaxis: 1in 10,000 for local haemostatic action
G: Glaucoma Dipivefrin

20. ADVERSE EFFECTS:
Tachycardia, restlessness, palpitation, headache,
tremor and rise in blood pressure.
cerebral haemorrhage, ventricular tachycardia
/fibrillation, angina, myocardial infarction
CONTRA INDICATIONS
Angina pectoris,
congestive cardiac failure,
Arrhythmias, Hypertension,
hyperthyroidism,
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21. NORADRENALINE
Catecholamine and neurotransmitter
Acts on alpha1, alpha2 and beta1 receptors
Vasoconstrictor- Hypertension
Reflex bradycardia
Intravenous administration
Used for emergency restoration of blood
pressure in shock.
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22. DOPAMINE
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Acts on dopamine, beta and alpha receptors.
Dilates renal, mesenteric blood vessels
Increase urine output
Increases cardiac output without increasing
heart rate
IV Dopamine : cardiogenic shock
used in renal failure, cardiac surgery & septic
shock

23. Dobutamine
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beta1- action
increased force of cardiac contraction and output,
without significant change in heart rate.
IV in cardiogenic shock and cardiac failure

24. ISOPRENALINE:
Acts on Beta1 and Beta 2 receptors
No action on alpha receptors
Cardiac stimulant ( increase the HR and contraction)
Smooth muscle relaxant
Used in: Heart block, Shock, asthma
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25. Ephedrine:
Bronchial asthma
Nasal decongestion
Mydriasis
Hypotension in spinal shock
Narcolepsy
Nocturnal enuresis
Stokes adams syndrome
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26. Amphetamines
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d-amphetamine, methamphetamine &
hydroxy-amphetamine
Uses:
Narcolepsy
Attention deficit syndrome/ hyper activity
disorder
Obesity