HOMATROPIN (HYOSCINE) Synthesis, SAR, MCQ,Structure,Chemical Properties and Therapeutic Uses

HOMATROPIN (HYOSCINE) Synthesis, SAR, MCQ,Structure,Chemical Properties and Therapeutic Uses

Homatropin

IUPAC nomenclature

(N-Methyl-8-azabicyclo[3.2.1]oct-3-yl) 2-hydroxy-2-phenylacetate.

 

Classification

Homatropin is a acetylcholine antagonist-muscarinic antagonist.

Physiochemical Properties

S. NO. PHYSICAL AND CHEMICAL PROPERTIES
1 Molecular weight 275.34 g/mol
2 Physical appearance White to fine-white crystalline powder
3 Melting point 99.5°C.
4 Solubility Water solubility is 5.57 mg/ml
5 Presence of ring Benzene and aza bicyclooctane rings present
6 Number of chiral centers 4
 

Mechanism of Action

  • Homatropin blocks muscarinic receptors and cholinergic signaling pathways.
  • It blocks the responses from iris sphincture muscle and cause pupil to become unresponsive to light upon dilation or mydriasis.
  • Homatropin also blocks the accommodation muscle of the ciliary body to cholinergic stimulation.[1]

Structure Activity Relationship

  • Either R1 or R2 must be heterocyclic or carbocyclic.
  • The R3 group can be hydrogen, hydroxyl, hydroxymethyl or amide.
  • Most potent derivatives has X as an ester.
  • X can also be either oxygen or absent completely.
  • The N substituent can be quaternary ammonium salt or tertiary amine or both with different alkyl groups.
  • Maximum potency obtained when the distance between the ring substituted carbons is 2 carbon units.

 

Method of synthesis

i. Tropin and 2-phenyl-2-(vinyloxy)acetyl chloride undergoes esterification reaction to give 8-methyl-8aza-bicyclo[.2.1]octan-3-yl 2-phenyl-2-(vinyloxy)acetate.

ii. The latter compound undergoes acidic hydrolysis to give Homatropin.

 

 

Therapeutic Uses

Homatropin is used for:

  • Before eye examination
  • After eye surgeries
  • Treatment of certain eye conditions

  Side Effects

Side effects of homatropin are:

  • Eye irritation
  • Redness of eye
  • Burning in eye
  • Stinging in eye
  • Blurred vision

MCQ

Q.1 Correct statements related with the Physicochemical properties of Homacycline are?

I. Molecular weight = 496 gm/mol

II. Physical appearance : present in viscous liquid form

III. Melting point = 99.5°C

IV. Solubility: very soluble in water

a) I, III

b) I, II, IV

c) II, IV

d) I

Q.2 Match the following of the drugs with their correct IUPAC names.

i. Methacholine A. 2-(Acetyloxy)-N,N,N-trimethylpropan-1-aminium.
ii. Homatropin B. (RS)-(8-Methyl-8-azabicyclo[3.2.1]oct-3-yl) 3-hydroxy-2-phenylpropanoate
iii. Procyclidine C. (N-Methyl-8-azabicyclo[3.2.1]oct-3-yl) 2-hydroxy-2-phenylacetate
iv. Atropin D. 1-cyclohexyl-1-phenyl-3-pyrrolidin-1-ylpropan-1-ol

 a) i-B, ii-A, iii-D, iv-C

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

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

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

Q.3 Correct steps for the mechanism of action of the drug Homatropin?

I. Antagonizing muscarinic receptors

II. Agonizing muscarinic receptors

III. Blocks the responses from iris sphincture muscle and cause pupil to become unresponsive to light upon dilation or mydriasis.

a) I – III

b) II – III

c) III – I

d) III – II

Q.4 Correct sequence for True/false for the classification of the drug can be?

  • Methacoline: Cholinergic antagonist
  • Procyclidine: Muscarinic antagonist
  • Homatropin: Cholinergic agonist
  • Atropin: Muscarinic antagonist

a) FTFT

b) TTTF

c) TFTF

d) FFTT

Q.5  Maximum potency obtained when the distance between the ring substituted carbons is?

a) 1 carbon unit

b) 4 carbon unit

c) 2 carbon unit

d) 7 carbon unit

Q.6 The correct sequence for the steps for synthesis of drug Homatropin from 2-phenyl-2-(vinyloxy)acetyl chloride?

I. Reaction with trimethylamine

II. Reaction with acetic anhydride

III. Esterification with tropin

IV. Hydrolysis

a) I – II

b) I – III – II

c) I – III – II – IV

d) III – IV 

Q.7 Side effect of drug Homatropin?

a) Burning in eye

b) Redness of eye

c) Blurred vision

d) All of the above

 

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ANSWERS

1-a

2-b

3-a

4-a

5-c

6-d

7-d

 

REFERENCES

[1] Christensen RE, Pearce I. Homatropine hydrobromide: Effect of topical administration upon the intraocular pressure and aqueous facility values of normal and chronic simple glaucomatous eyes. Archives of Ophthalmology. 1963 Sep 1;70(3):376-80.

 

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