Antigenicity of chlorpromazine and clozapine to rabbits

Antigenicity of clozapine was studied in rabbits, comparing with that of chlorpromazine as control. The results indicate that chlorpromazine produces antibody in rabbit as revealed by passive hemagglutination test, giving the titer of 1 : 2, 000 or higher in all the five cases observed, though specific precipitin lines has not been obtained and PCA test proves to be negative. Clozapine failed to produce anti.clozapine antibody giving negative passive hemagglutination test, passive cutaneous anaphylaxis and precipitin reaction, in all forms tested. Some remarks were made on the possible close relation between the antigenicity of the drug and its affinity to protein.