CHLORPHENIRAMINE Synthesis, SAR, MCQ,Structure,Chemical Properties and Therapeutic Uses

CHLORPHENIRAMINE Synthesis, SAR, MCQ,Structure,Chemical Properties and Therapeutic Uses


IUPAC nomenclature



  • H1-receptor antihistamine
  • Alkylamine antihistamine


Physiochemical Properties

1 Molecular weight 274.79 g/mol
2 Physical appearance White crystalline solid
3 Melting point 130-135oC
4 Solubility 160 mg/ml
5 Octanol/water partition coefficient 3.38
5 Presence of ring Pyridine , phenyl
6 Number of chiral centers 1


Mechanism of Action

i. Chlorpheniramine binds to histamine H1 receptors and blocks the action of endogenous histamine.

ii. Due to this, there is relief in the negative symptoms produced by histamine.


Structure Activity Relationship

Structure activity of alkyl amines antihistamines can be summarized as:

  • E- and Z- isomers in alkenes shows large difference in activity, where, E-isomers are more potent than Z-
  • The two aromatic rings have different binding environments at the receptors.
  • 5-6 angstrom distance is required between aromatic ring and tertiary aliphatic amine for biding at the receptor.
  • S­-enantiomers have greater affinity for H1 histamine receptors [1]


Method of synthesis

i. Pyridine undergoes alkylation by 4-chlorobenzylcloride to give 2-(4-chlorobenzyl)pyridine.

ii. Alkylation of the last with 2-dimethylaminoethylchloride in presence of sodium amide gives chlorpheniramine. [2]

Medicinal Uses

Chlorpheniramine is used for treatment of:

  • Allergies
  • Hay fever
  • Common cold
  • Watery eyes
  • Runny nose
  • Sneezing
  • Cold symptoms
  • Itchy 

Side Effects

Side effects of Chlorpheniramine are:

  • Seizures
  • Loss of consciousness
  • Hallucinations
  • Drowsiness
  • Dizziness
  • Allergic reactions




Q.1 Which of the following statements related with the physical properties of drug Chlorpheniramine?

I. Molecular weight: 343.9 gm/mol

II. Physical appearance: White crystalline solid

III. Melting point: 178oC

IV. Octanol/water partition coefficient: 3.38

a) I, II, IV

b) II, IV

c) III, IV

d) I, V

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

i. Chlorpheniramine A. 3-(4-Chlorophenyl)-N,N-dimethyl-3-pyridin-2-yl-propan-1-amine
ii. Loxapine B. 8-chloro-6-(4-methylpiperazin-1-yl)benzo[b][1,4]benzoxazepine
iii. Cevimeline C. (N-Methyl-8-azabicyclo[3.2.1]oct-3-yl) 2-hydroxy-2-phenylacetate
iv. Homatropin D. (2R,2R)-2′-Methylspiro[4-azabicyclo[2.2.2]octane-2,5′-[1,3]oxathiolane].

 a. i-A, ii-B, iii-D, iv-C

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

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

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

Q.3 Mechanism of action of Chlorpheniramine includes?

I. It binds with Histamine H1 receptor and produces antagonistic effects.

II. Permanent relief in negative symptoms produced due to histamine

III. Binding with alpha-adrenergic receptors

a) I

b) II, III

c) I, III

d) III

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

  • Chlorpheniramine: Alkylamine antihistamine drug
  • Naproxen: Alylating agent
  • Diclofenac: DMARDs
  • Sevoflurane: Inhalational anesthetics





Q.5 Which of the following statement is true related with the SAR of alkyl amine antihistamine drugs?

a) E- and Z- isomers in alkenes have no difference in activity

b) Z-isomers are less potent than E-isomers

c) E- and Z- isomers are inactive

d) S-enantiomers are inactive

Q.6 The correct sequence for the steps for synthesis of drug Chlorpheniramine from pyridine can be?

I. Alkylation by 4-chlorobenzylchloride

II. Alkylation with 2-dimethylaminoethylchloride

 III. Oxidation

a) I – II

b) I – III

c) III – II – I

d) II – I – III

Q.7 Side effect of drug Chlorpheniramine?

a) Drowsiness

b) Seizures

c) Blurred vision

d) All of the above



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[1] Lemke TL, Williams DA, editors. Foye’s principles of medicinal chemistry. Lippincott Williams & Wilkins; 2012 Jan 24.

[2] Vardanyan R, Hruby V. Synthesis of essential drugs. Elsevier; 2006 Mar 10.


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