Interaction of tertiary amines and quaternary ammonium compounds with gastrointestinal mucin

The binding property of some tertiary amines (chlorpromazine, promethazine and imipramine) and quaternary ammonium compounds (propantheline, mepenzolate and butylscopolamine) for gastric mucin was investigated. All tertiary amines tested bound gastric mucin to varying extents, and the binding of chlorpromazine was especially strong. Moreover, the absorption behaviors of chlorpromazine in rat intestinal loops was significantly inhibited in the presence of gastric mucin. On the contrary, all quaternary ammonium compounds tested did not bind gastric mucin and the absorption of propantheline was not affected in the presence of gastric mucin. These results suggested that gastrointestinal mucin produced a significant effect on the bioavailability of these tertiary amines after oral administration.