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

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


IUPAC nomenclature



  • H1-receptor antihistamine
  • Piperazine antihistamine


Physiochemical Properties

1 Molecular weight 374.9 g/mol
2 Physical appearance Solid or oil
3 Melting point 190oC
4 Solubility 428 mg/L in water
5 Octanol/water partition coefficient 2.7
5 Presence of ring Piperazine, phenyl
6 Number of chiral centers 1

Mechanism of Action

i. Hydroxyzine acts as an inverse agonist for H1 receptors.

ii. This inverse agonism is responsible for efficacy of the drug in the treatment of histaminic edema, flare and pruritus.

iii. Sedative properties of the drug allows activity as an anxiolytic.

iv. Anti-emetic properties are secondary to activity at the off-targets.

Structure Activity Relationship

Structure activity of piperizine antihistamines can be summarized as:

  • These are the derivatives of ethylene diamines.
  • The connecting moiety is CHN group
  • Primary structural difference is nature of para aromatic ring substituent
  • These are moderately potent.
  • Slow onset of action
  • Low incidence of drowsiness
  • They also exhibit peripheral and central antimuscarinic activity.

Method of synthesis

Alkylation of 1-(4-chlorobenzhydryl)piperazine with 2-(2-hydroxyethoxy)ethylchloride gives hydroxyzine.[1]

Medicinal Uses

Hydroxyzine is used for treatment of:

  • Itching
  • Anxiety
  • Histaminic edema
  • Flare
  • Pruritus
  • Chronic urticaria
  • Management of agitation caused due to alcohol withdrawl
  • Motion sickness
  • Nausea
  • Vomiting


Side Effects

Side effects of Hydroxyzine are:

  • Dizziness
  • Blurred vision
  • Dry mouth
  • Constipation
  • Mood changes
  • Restlessness
  • Hallucinations
  • Tremors
  • Difficulty urination
  • Seizures
  • Irregular heartbeats
  • Fainting
  • Allergic reactions



Q.1 Correct statements from the following related with the physicochemical properties of drug Hydroxyzine are?

I. Molecular weight: 374.9 gm/mol

II. Appearance: Solid or oil

III. Melting Point:190 oC

IV. Solubility: Insoluble in water

a) I, II, III

b) I, III, IV

c) II, IV

d) I, II, III, IV

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

i. Hydroxyzine A. (RS)-6-(Difluoromethoxy)-2-[(3,4-dimethoxypyridin-2-yl)methylsulfinyl]-1H-benzo[d]imidazole
ii. Dimethindene B. N,N-Dimethyl-2-[3-(1-pyridin-2-ylethyl)-1H-inden-2-yl]ethan-1-amine
iii. Doxylamine C. (RS)-N,N-dimethyl-2-(1-phenyl-1-pyridin-2-yl-ethoxy)-ethanamine
iv. Pentoprazole D. 11-(1-Methylpiperidin-4-ylidene)-6,11-dihydro-5H-benzo[5,6]cyclohepta[1,2-b]pyridine

 a) i-D, ii-B, iii-C, iv-A

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

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

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

Q.3 Mechanism of action of drug Hydroxyzine involves?

I. Antagonist for H1 receptor

II. Inverse agonist for H1 receptor

III. Also anxiolytic activity

a) I, III

b) I, IV

c) I, II, III

d) II, III

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

  • Hydroxizine: H1-receptor antihistamine drug
  • Enflurane: Sedative-hypnotics
  • Tripelenamine: H1-antagonist
  • Dexamethasone: Corticoids





Q.5  The connecting link in the structure of piperazine antihistamines is?

a) CHN

b) CHO

c) Acetic anhydride

d) None of the above

Q.6 Type of rings present in the structure of Hydroxyzine?

I. Phenyl

II. Piperazine

III. Piperidine

IV. Benzodiazepine

a) I, IV

b) I, II

c) II, III

d) II

Q.7 Side effect of drug Hydroxyzine is/are?

a) Constipation

b) Dry mouth

c) Tremors

d) All of the above






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


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