Chronic Bachelor

Chloramphenicol - An SAR Review

Have you ever thought of why some drugs in particular anti-biotics disappear after a brief stay. Though in majority of instances it's due to scrupulous use of them by us leading to development of resistant strains against them quickly there are also some structures that resist any modification of structure. One such drug is Chloramphenicol. It has existed as a bachelor from the day of its introduction till now. While other anti - biotics ( Penicillin's and Cephalosporins ) have generated second and even some, third generations our drug of interest has been as a bachelor without a family of its own. We take a second look at it and analyze why it had been a bachelor.

• Replacement o the -NO₂ group with a number of other substituents including CN, CONH₂, NH₂, OH results in loss of anti bacterial activity
• The phenyl group has been replaced with other aromatic or alicyclic groups such as naphthyl, pyridyl, thienyl, cyclohexyl etc. Only the nitro thienyl compound has antibacterial activity and it was less potent.
• Only the d - threo compounds of the 4 stereo isomers is anti bacterial activity.
• The primary alcohol group seems to be imperative. Alteration of any kind leads to loss of activity.
• The propanediol side chain too is non alterable.
• Replacement of the di - chloro acetyl group with other halogens such as bromine resulted in loss of potency.

So what do you make of it? Simply vague ? The structure is so sensitive that it results in loss of action on alteration of any of its structural parameters . What has this led to is the non availability of new potent structures to combat the resistance generated against Chloramphenicol by the ever mutating bacteria.

It took nearly 10 years to develope norfloxin from naldixic acid which subsequently led to the now "At the Peak" family of anti biotics FluroQuinolones. It just was that simple that incorporation of an fluorine moiety at the C6 position resulted in development of FluroQuinolones. So why not our bachelor may too flourish in the years to come and make up for the present loss. Hope so, for the betterment of mankind.

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Intuitive Pharmacol™

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