SAR of Antihistamine

>> YOUR LINK HERE: ___ http://youtube.com/watch?v=tpEhMLV2AhE

This video contains the General structural activity of H1 antihistamine agents. The points are as follows: • The diaryl substitution pattern is present in both the first and second generation antihistamines and is essential for significant H1-receptor affinity • Most H1 antagonists contain substituents in one of the aryl rings (usually phenyl ring) and these influence potency • In many first generation antihistamines, the terminal nitrogen atom is a simple dimethylamino moiety • The amine may also be part of a heterocyclic structure e.g. Piperazines, some propylamines • The amino moiety is basic, with pKa ranging from 8.5 to 10 and thus suppose to be protonated when bound to the receptor. The moiety also important in the development of stable, solid dosage forms through salt formation • The carbon chain of typical H1 antagonists consists of two or three atoms. So that the distance between the centre of the aromatic rings and aliphatic nitrogen may be 5-6 A • In some series, branching of the carbon chain results in reduced antihistaminic activity. There are exceptions, promethazine, which has greater activity than its non-branched counterpart • The X connecting moiety may be saturated carbon-oxygen moiety or simply a carbon or nitrogen atom • Generally, the first and second generation antihistamines are more lipophilic than the H2 antagonists • #AmitLunkad

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