Trihexyphenidyl

IUPAC nomenclature

(RS)-1-Cyclohexyl-1-phenyl-3-(1-piperidyl)propan-1-ol.

Classification

Trihexyphenidyl is an acetylcholine antagonist. It is a muscarinic antagonist.

Physiochemical Properties

Mechanism of Action

• It is a selective M₁ muscarinic acetylcholine receptor antagonist.
• It partially blocks cholinergic activity in the central nervous system and reduces the symptoms of Parkinson’s disease.
• It also increases the bioavailability of dopamine which initiates and smoothly control the voluntary muscle movement. [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. Acetophenone and piperidine undergoes Mannich condensation in presence of formaldehydeto produce 3-piperidinopropiophenone.

ii. The latter compound undergoes Gringnard’s reaction with cyclohexylmagnesium chloride to give trihexyphenidyl.

Therapeutic Uses

Trihexyphenidyl is used for:

• Treatment of symptoms of Parkinson’s disease

Side Effects

Side effects of Trihexyphenidyl are:

• Dry mouth
• Dizziness
• Constipation
• Blurred vision
• Nervousness
• Nausea
• Flushing

MCQ

Q.1 “RS)-1-Cyclohexyl-1-phenyl-3-(1-piperidyl)propan-1-ol” is the IUPAC nomenclature of which drug?

a) Trihexyphenidyl

b) Propantheline

c) Oxybutynin

d) Oxazepam

Q.2 Melting point of Trihexyphenidyle is?

a) 152-162°C

b) 129-130°C

c) 205.5°C

d) 258.5°C

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

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

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

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

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

Q.4 Mechanism of action of Trihxyphenidyl is based on?

a) Blocking the Muscarinic acetylcholine receptors

b) Blocking the nicotinic acetylcholine receptors

c) Increasing the bioavailability of dopamine

d) Both a) and c)

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

• Either R₁ or R₂ must be heterocyclic or carbocyclic.
• The R₃ group can be hydrogen, hydroxyl, hydroxymethyl or amide..
• 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.

a) TFTF

b) FTFT

c) TTTT

d)FFTF

Q.6 Steps involved in the synthesis of trihexyphenidyl from acetophenone in the correct sequence is?

I. Mannich condensation with piperidine

II. Grignard’s reaction with cyclohexylmagnesium chloride

III. Reaction with hydrazine

a) I – II – III

b) I – III

c) I – II

d) II – I – III

 Q.7 The drug trihexyphenidyl is mainly used for?

a) Parkinson’s disease

b) Hypertension

c) Depression

d) Constipation

For More Standard and Quality Question Bank you can Join Our Test Series Programme for GPAT, NIPER JEE, Pharmacist Recruitment Exam, Drug Inspector Recruitment Exams, PhD Entrance Exam for Pharmacy

Participate in  Free Online Test for GPAT, Pharmacist,Drug Inspector

ANSWERS

1-a

2-d

3-b

4-d

5-c

6-c

7-a

REFERENCES