Antiallergy and Antiasthmatic Drugs

The second generation of antihistamines includes stronger drugs that inhibit the release of histamine and other inflammatory mediators from several cell types. Examples of this group include terfenidine, 23 and loratadine, 24 [11], 

Loratadine (Claritin), 24, is prepared in good yield by the following reaction [12]  

Cetrizine, 25, is sold as Zyrtec and is widely used as an antiallergic and is most effective against rash/hives. Cetrizine is an orally active racemic compound [11]. 

Enprofylline, 28, is produced in a multistep process of conversion of aminopropyluracil, 29 [3]. 

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