Trimeprazine

Or

Alimemazine

IUPAC nomenclature

10-(3-dimethylamino-2-methylpropylphenothiazine

Classification

• H1-receptor antihistamine
• Phenothiazine derivative antihistamine drug

Physiochemical Properties

Mechanism of Action

• Trimeprazine antagonizes the effect of histamine HA-receptors by competing with free histamine for binding at HA-receptor sites. This helps in reducing the negative symtoms occurring due to HA-receptor binding.

Structure Activity Relationship

Structure activity of phenothiazine derivatives antihistamines can be summarized as:

• There are 2-3branched alkyl chain between the ring system and the nitrogen atom.
• On unbranching, antipsychotic series of drugs can be obtained.

General structure activity of first generation H1-receptors antagonist can be summarized as:

• Ethylene chain gives maximum activity.
• Increasing or decreasing the chain length decreases the activity of drug, but promethazine is an exception.
• Chain may bepresent in saturated or unsaturated form, or sometimes a part of a ring system.
• Diaryl substitution is essential for significant H1 receptor affinity.
• Terminal nitrogen atom should be tertiary in nature.

Method of synthesis

Alkylation of phenothiazine with 1-dimethylamino-2-methyl-propylchloride gives trimeprazine. [1]

Medicinal Uses

Trimeprazine is used for treatment of:

• Itching
• Relieve in coughing

Side Effects

Side effects of Trimeprazine are:

• Dizziness
• Upset stomach
• Abdominal pain
• Trouble swallowing
• Seizures
• Dizziness
• Increased heartbeat
• Allergic reactions

MCQs

Q.1 What can be the correct IUPAC nomenclature of Trimeprazine?

a) 2-(diphenylmethoxy)-N,N-dimethylethanamine

b) 10-(3-dimethylamino-2-methylpropylphenothiazine

c) (RS)-1-[(4-chlorophenyl)- phenyl-methyl]-4- [(4-tert-butylphenyl) methyl] piperazine

d) (R)-(+)-2-([3-methyl-4-(2,2,2-trifluoroethoxy)pyridin-2-yl]methylsulfinyl)-imidazole

Q.2 Which amongst the following statements is/are incorrect related to the Phenothiazine derivative antihistamine drugs?

I. There are 2-3branched alkyl chain between the ring system and the nitrogen atom.

II. On unbranching, antipsychotic series of drugs can be obtained.

a) I

b) I, II

c) II

d) None

Q.3 Types of rings present in the structure of Trimeprazine?

I. Imidazole

II. Pyridine

III. Phenothiazine

IV. Phenyl

a) I, II

b) I, IV

c) II, IV

d) III

Q.4 Side effects of drug Trimeprazine is/are?

a) Allergic reactions

b) Trouble swallowing

c) Upset stomach

d) All of the above

Q.5 Match the following drugs with their correct molecular weight-

 a) i-A, ii-B, iii-C, iv-D

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

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

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

Q.6 An example of drug from class phenothiazine derivative antihistamine drug?

a) Trimeprizine

b) Besoprolol

c) Hydroxyamphetamine

d) Ephedrin 

Q.7 Octanol/water partition coefficient of Trimeprazine is?

a) 7.3

b) 5.3

c) 4.6

d) 1.6

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ANSWERS

1-b

2-d

3-d

4-d

5-c

6-a

7-c

REFERENCES