Sympatholytic/ Adrenergic Antagonist drugs by Sunny Shivankar b.pharm 2nd yr, Gurunanak college of pharmacy, Nagpur

1. Adrenergic Receptor antagonist/
~ presented By
CombinedBlockerz
Anti – Adrenergic Drugs/
Sympatholytics
Alpha Adrenergic Antagonist
~ By
Sunny shivankar
B.Pharm 2nd year
Gurunanak college of pharmacy

2. Antagonist :
A substance that acts against and block an
action. Antagonist is an opposite of agonist.
• Adrenergic Antagonist :
These are those drugs which inhibit the effect of
sympathomimetic agents by blocking the adrenergic
receptor (alpha/beta / both).
Eg. Tolazoline, phentolamine, phenoxybenzamine, etc.
• Types of Adrenergic Antagonist/Blockers:
1. Alpha Adrenergic blockers
2. Beta Adrenergic blockers

3. Alpha Adrenergic Antagonist :
These are those drugs which blocks the alpha
receptor and antagonises the effects produced by the
drugs acting on alpha receptors.
Classification:

4. Mechanism of Adrenergic Antagonist

5. General effects of Adrenergic Antagonist:
 Vasodilator- Reduce periferal resistance = decrease cardiac output
(Fall in BP)
 Reflex tachycardia – due to fall in mean arterial pressure
 Nasal stiffness and miosis – due to blockage of alpha receptors in
nasal blood vessels and Contractions of pupil
 Increase in intestinal motility – loose motions may occur
 Renal blood flow decrease – blood volume increase
 Decrease in tone of smooth muscle of sphincter and prostate
 Prazosine is found to decrease in LDL and increase triglycerides
HDL

6. Alpha Adrenergic Antagonist(Non-Selective)
A) Imidazoline Derivative
1. Tolazoline
• Mechanism of action: It is competitive inhibitor of a-
recepto. Its structure is similar to that of a-agonist so,
it bind reversibly with the a- receptor (in place of a-
agonist) and block the effect of a-receptor.
• Properties : It a white crystalline powder freely
soluble in water.
1. Used as a Vasodilator.
2. It cause stimulation Of gastric acid secretion.
3.Also used to antagonize the effect of clonidine.
• Uses:
IUPAC name : 2-Benzyl-2-Imidazoline

7. Synthesis of Tolazoline
 It is prepared by the reaction of 1 mole of benzyl cyanide 1 mole
of ethylene diamine in presence of carbon disulphides.

8. Alpha Adrenergic Antagonist(Non-Selective)
A) Imidazoline Derivative
2. Phentolamine
• Mechanism of action: It is a competitive
alpha adrenergic antagonist and has an
similar affinity to both alpha 1 and alpha
2 receptor.
• Properties : It is a white crystalline powder,
slightly hygroscopic and freely soluble in
water.
• Uses :
1. It is used to control hypertensives condition
of patients in pheochromocytoma
2. It is used as vasodilatory to inhibit the
vasoconstriction.
IUPAC name : 3-[N–(2–Imidazolin-2ylmethyl)
-4 toluidino]phenol

9. Alpha Adrenergic Antagonist(Non-Selective)
 Beta - Haloalkylamine
1. Phenoxybenzamine
• Mechanism of action: It is an irreversible alpha
blocker and blocks both alpha 1 and alpha 2
receptors.
• Properties : It is colourless crystalline
compound, soluble in alcohol, water, and
chloroform.
• Uses :
1. Used in the treatment of hypertension caused
by pheochromocytoma
2. Used in treatment of urinary retention.
3. Used in the treatment of peripheral vascular
disease like Reynoud’s syndrome.
IUPAC name :N-Benzyl-N-(2- Chloroethyl)
1-phenoxypropan-2-amine

10. Alpha Adrenergic Antagonist(Non-Selective)
 Ergot Alkaloids
1.Dihydroergotamine
• Mechanism of action: It is an antagonist of
alpha adrenergic receptor.
• Uses :
1. It is used in the treatment of migraine.
2. Used in treatment of overdose of headache.
3. Used in combination of heparin in the prophylaxis
of thrombosis.
4. It is also used as vasoconstrictor. IUPAC name: (5’a,10a)-5'-Benzyle-12'-hydroxy-2’-
methyl-3’,6’,18-trioxo-9,10-dihydroergotaman

11. Adrenergic Blocking Agents (Non-Selective)
 Ergot Alkaloids
2. Methysergide
• Mechanism of action:
It is an antagonist of alpha adrenergic
receptor. It is potent serotonin antagonist.
• Uses :
1. Used as a prophylactic in the treatment of
severe recurrent migraine.
2. It has weak vasoconstrictive and oxytocic
effects. IUPAC name: N-[(2S)-1-Hydroxy-2-butanyl]-1,6
-dimethyl-9,10-didehydroergoline-8-carboxamide

12. Alpha Adrenergic Antagonist (Selective)
 Alpha 1 Selective antagonist : It belongs to class of piperazinyl quinazoline, a
selective alpha 1 adrenergic antagonist. It has affinity for alpha 1 receptor which is 1000
times more than that of alpha 2 receptor.
• Properties : It is white or almost white
powder. It is freely soluble in water.
• Uses :
1. Management of hypertension.
2. Treatment of heart failure.
3. Treatment of Reynoud’s syndrome.
4. Symptomatic treatment of urinary obstruction.
IUPAC name: 4-(4-amino-6,7-dimethoxy-2-
quinazolinyl)-1-(-2-Furanyl carbonyl) piperazine
• Prazosine

13. Alpha Adrenergic Antagonist (Selective)
 Alpha 2- Selective Antagonist :
IUPAC name:
17α-hydroxyyohimban-16α-
carboxylic acid methyl ester
1. Yohimbine
• Mechanism of action:
It is a selective alpha 2 Adrenergic
Antagonist.
• Uses :
It increases the heart rate and blood
pressure due to blockage of alpha 2
Adrenergic receptor in the CNS. It is used
to treat male erectile impotence.

14. Thankyou..!!!
Reference –
• Textbook of medicinal chemistry V.
Algarswami
• Medicinal chemistry (Pee Vee)
• YouTube
• Google