SAR of Anilides

SAR of Anilides

General structure of anilides is represented as follows:

a. Aryl group

• The clinically useful local anaesthetics of this type possess a phenyl group attached to the sp2 carbon atom through a nitrogen bridge.

• Placement of substituents on the phenyl ring with a methyl group in the 2 (or) 2 and 6-position enhances the activity. In addition, the methyl substituent provides steric hindrance to hydrolysis of the amide bond and enhances the coefficient of distribution.

• Any substitution on the aryl ring that enhances zwitterion formation will be more potent.

b. Substituent X

• ‘X’ may be carbon, oxygen, or nitrogen among them lidocaine series (X = O) has provided more useful products.

c. Amino alkyl group

• The amino function has the capacity for salt formation and is considered as the hydrophilic portion of the molecule.

• Tertiary amines (diethyl amine, piperidine) are more useful because the primary and secondary amines are more irritating to tissues.