Mefenamic acid

IUPAC nomenclature

2-(2,3-dimethylphenyl)aminobenzoic acid

Classification

• NSAID
• Anthranylic acid derivatives

Physiochemical Properties

Mechanism of Action

• Mefenamic acid binds with COX-1 and COX-2 and inhibits the action of prostaglandin synthetase.
• Due to this, the level of prostaglandins decreases and the symptoms of pain are temporarily reduced.

Structure Activity Relationship

General SAR for anthranylic acid derivatives can be summarized as follows:

• Activity decreases when substitution on anthranilic acid ring.
• Activities due to substitution on the N-aryl ring follows the general order m > o > p.
• For disubstitution products, activity was found to be maximum when o and m positions are substituted near to each other on the N-aryl ring.
• Substitutions on the N-aryl ring with such groups which leads the ring to be noncoplanar with the anthranilic acid ring increases the binding of the drug and hence, increases the activity (meclofenamic acid being more active than flufenamic acid).
• NH-moiety of the anthranilic ring is important for the activity of the drug, and replacement of NH- moiety with O, CH₃, S, SO₂, N-CH₃ or N-COCH₃ groups decreases the activity of drug.
• Position of the acidic function is important for the activity and not the nature of acidic function. [1]
• Replacement of carboxylic acid function with isosteric tetrazole function has no significant effect on the activity of compound.[1]

Method of synthesis

Potassium salt of 2-bromobenzoic acid is reacted with ,3-dimethylaniline in the presence of copper(II) acetate to give mefenamic acid. [2]

Therapeutic Uses

Mefenamic acid is used for:

• Short-term treatment for mild to moderate pain
• Decreasing menstrual pain 

Side Effects

Side effects of mefenamic acid are:

• Skin rash
• Changes in vision
• Shortness of breath
• Weight gain
• Swelling
• Stomach bleeding
• Nausea
• Jaundice
• Pale skin
• Difficulty in urination
• Anemia
• Skin reactions
• Indigestion
• Nausea
• Tremors
• Stomach pain
• Confusion
• Diarrhea
• Constipation
• Drowsiness
• Dizziness
• Headache

MCQs

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

a) 2-(2,3-dimethylphenyl)aminobenzamide

b) 2-(2,3-dimethylphenyl)aminobenzoic acid

c) 4-hydroxy-2-methyl-1,1-dioxo-N-pyridin-2-ylthieno[2,3-e]thiazine-3-carboxamide

d) 4-hydroxy-2-methyl-1,1-dioxo-N-pyridin-2-ylthieno[2,3-e]thiazine-3-Carboxylic acid

Q.2 Which amongst the following statements is/are incorrect related to the SAR of Anthranylic acid derivatives?

I. Activity decreases when substitution on anthranilic acid ring.

II. Activities due to substitution on the N-aryl ring follows the general order m > o > p.

III. For disubstitution products, activity was found to be minimum when o and m positions are substituted near to each other on the N-aryl ring.

IV. Substitutions on the N-aryl ring with such groups which leads the ring to be noncoplanar with the anthranilic acid ring increases the binding of the drug and hence, increases the activity

a) I

b) III

c) I, II

d) IV

Q.3 Mefenemic acid can be synthesized by the reaction of 2,3-dimethylbenzamine in presence of copper(II)acetate with?

a) Potassium 2-bromo-benzoate

b) Saccharine

c) Mulch’s reagent

d) All of the above

Q.4 Side effects of drug mefenamic acid is/are?

a) Skin rash

b) Abdominal pain

c) Easy bleeding

d) All of the above

Q.5 Match the following drugs with the correct number of the chiral carbons they have in their structure:

 a) i-A, ii-C, iii-D, iv-B

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

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

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

Q.6 An example of drug from class NSAIDs?

a) Methotrexate

b) Glycopyrrolate

c) Mefenamic acid

d) Salbutamol 

Q.7 The type of ring system found in Mefenamic acid?

I. Phenyl

II. Pyridine

III. Anthracene

IV. Thiophene

a) I, III

b)II, III, IV

c) I

d) II, IV

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ANSWERS

1-b

2-b

3-a

4-d

5-c

6-c

7-c

REFERENCES