Tolazoline

IUPAC nomenclature

2-Benzyl-4,5-dihydro-1H-imidazole.

Classification

Tolazoline is nonselective α-adrenergic antagonist.

Physiochemical Properties

Mechanism of Action

• Tolazoline has moderate α-adrenergic antagonist property and also having histamine agonist activity.
• It produces vasodilation through direct effect on peripheral vascular smooth muscles and indirect effects through release of endogenous histamine.
• It reduces pulmonary arterial pressure and vascular resistance.[1]

Structure Activity Relationship

• Molecules with 2,6-disubstitutions, which assume an orientation where the phenyl and imidazoline rings are in different plans are having the highest activity.
• Electronic effects have only influence on the actions at H_2; action on α-receptors are not influenced.
• Substitutions at 3, 4 or 5 positions of the phenyl ring preclude potent activity at H₂-receptor sites while the α-receptor activity is maintained. [2]

Method of synthesis

Heterecyclation of the ethyl ester of iminophezylacetic acid with the help of ethylenediamine give tolazoline.

Therapeutic Uses

Tolazoline is used for the treatment of:

• Reducing PVR
• Thrombophlebitis
• Thromboangitis obliterans
• Spasm
• Scleroderma
• Raynaud disease
• Persistant fetal circulation syndrome
• Peripheral vascular diseases
• Causalgia
• Arteriosclerosis obliterans

Side Effects

Side effects of Tolazoline are:

• Stomach bleeding
• Intestinal bleeding
• Decreased urine production
• Keidney failure
• Hypotension
• Fall in level of chlorine in blood
• Widening of blood vessels
• Vomiting
• Goose bumps
• Nausea
• Fast heartbeat
• Diarrhea
• Dilated pupils

 MCQs

Q.1 “2-Benzyl-4,5-dihydro-1H-imidazole” is the IUPAC nomenclature of which drug?

a) Metaraminol

b) Tolazoline

c) Prazosin

d) Dihydroergotamine

Q.2 Type of ring structure present in Tolazoline?

a) Imidazole ring

b) Benzene ring

c) Ergoline ring

d) Both a) and b)

Q.3 Match the following with correct classifications of the drugs.

 a) i-C, ii-B, iii-A, iv-D

b) i-D, ii-C, iii-B, iv-A

c) i-A, ii-D, iii-C, iv-B

d) i-B, ii-A, iii-D, iv-C

Q.4 Correct steps for the mechanism of action of the drug…..

I. Effect on peripheral smooth muscles.

II. Reduction in pulmonary and aterial blood pressure

III. Vasodilation

 a) II – I – III

b) III – II – I

c) III – I – II

d) I – III – II

Q.5   Correct sequence for True and False for the given statements related with the SAR of drug…..

• Molecules with 2,6-disubstitutions, which assume an orientation where the phenyl and imidazoline rings are in different plans are having the lowest activity.
• Electronic effects have only influence on the actions at H_2; action on α-receptors are not influenced.
• Substitutions at 3, 4 or 5 positions of the phenyl ring preclude potent activity at H₂-receptor sites while the α-receptor activity is maintained.

a) FTT

b)TFT

c)FFT

d) TTT

Q.6 Tolazoline can be produced through heterocyclation of ethyl ester of?

a) Paraaminophenol

b) Hydroxyphenyl acetone

c) Ethylenediamine

d) Iminophezylacetic acid

 Q.7 The drug Tolazoline is mainly used for?

a) Treatment of hypotension

b) During fall in level of chlorine in blood

c) Decreasing pulmonary vascular resistance

d) Treatment of intestinal bleeding

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ANSWERS

1-b

2-d

3-a

4-d

5-a

6-d

7-c

REFERENCES