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

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


IUPAC nomenclature



Phenytoin is a hydantoin derivative anticonvulsant drug.


Physiochemical Properties

1 Molecular weight 252.27 g/mol
2 Physical appearance White crystalline powder
3 Melting point 296.5°C
4 Solubility Insoluble in cold water; soluble in acetic acid
5 Octanol/water partition coefficient 2.47
6 Presence of ring Imidazolidine, phenyl
7 Number of chiral centers Not present


Mechanism of Action

Phenytoin targets voltage-gated sodium channel and inhibits the positive feedback loop that results in neuronal propagation of high frequency action potential. In this way, seizures are prevented.


Structure Activity Relationship

SAR of hydantoins can be described as follows:

  • For the activity of the drug, a phenyl or other aromatic substituent is necessary.
  • Substitution with an alkyl group at position 5 will result in the sedative properties of drug.
  • Some hydantoins may also exhibit properties against chemically induced convulsions.
  • Many hydantoins are ineffective against electroshock induced convulsions.


Method of synthesis

Phenytoin can be synthesized by rearrangement on the reaction of urea and benzil.[1]


Therapeutic Uses

Phenytoin is used for:

  • Prevention and control of seizures

 Side Effects

Side effects of phenytoin are:


  • Nausea
  • Vomiting
  • Dizziness
  • Constipation
  • Insomnia
  • Drowsiness
  • Slow heartbeat
  • Unusual eye movements
  • Confusion
  • Slurred speech
  • Loss of coordination
  • Blurred vision
  • Increased hair growth
  • Increased thirst
  • Increased urination
  • Bone pain
  • Joint pain
  • Weak bones



Q.1 What are the correct statements related with the physicochemical properties of Phenytoin drug?

I. Molecular weight = 252.27 gm/mol

II. It appears as pale yellow crystals

III. It is very soluble in cold water

IV. Piperidine ring is present in the structure

a) I

b) I, II, IV

c) II, III

d) I. II. III. IV

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

i. Phenytoin A. 5,5-diphenylimidazolidine-2,4-dione
ii. Butabarbital B. (RS)-N’-(7-chloroquinolin-4-yl)-N,N-diethyl-pentane-1,4-diamine
iii. Favipiravir C. 5-butan-2-yl-5-ethyl-1,3-diazinane-2,4,6-trione
iv. Chloraquine D.  6-fluoro-3-hydroxypyrazine-2-carboxamide

 a) i-B, ii-C, iii-A, iv-D

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

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

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

Q.3 Steps for mechanism of action for drug phenytoin?

I. Neuronal propagation is inhibited

II. Inhibition of positive feedback loop of voltage-gated sodium channel

III. Seizures are prevented

IV. Meningitis is prevented

a) I – II – IV

b) I – II – III

c) II – I – III

d) II – I – IV

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

  • Phenytoin: Antiviral drug
  • Ritonavir: HIV protease inhibitor
  • Ritonavir: Guanosine nucleoside antiviral drug
  • Triazolam: Benzodiazepine sedative hypnotic





Q.5 Type of ring present in the structure of Phenytoin is?

a) Imidazolidine

b) Piperazine

c) Piperidine

d) Pyridine

Q.6 Starting chemicals required for the synthesis of phenytoin are?

I. Urea

II. Phenol

III. Benzil

IV. Sodium amide

a) I , III

b) III , II

c) II , IV

d) III , II

Q.7 Side effect of drug Phenytoin are?

a) Slow heartbeats

b) Loss of coordination

c) Increased growth of hairs

d) All of the above




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 Online FREE  GPAT  TEST: CLICK HERE

  Participate in Online FREE  Pharmacist  TEST: CLICK HERE 

Participate in Online FREE  Drug Inspector  TEST: CLICK HERE 













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

Leave a Reply

Your email address will not be published. Required fields are marked *

twelve − ten =

Free Video Lectures of Pharmacy Exams
Apply now

Developed By Connect Globes