In simple aqueous media, the extent of adsorption of various phenothiazine derivatives by kaolin, talc, and activated charcoal is significant. Adsorption by talc and kaolin is dependent upon pH of the medium, while adsorption by activated charcoal is less affected by pH. Adsorption of promazine hydrochloride by all three adsorbents is sensitive to the electrolyte concentration of the medium. A variety of evi- dence suggests that adsorption of the phenothiazine derivatives by activated charcoal is a result of physical forces related to the tendency of the solute to accumulate at the air-water interface. Adsorption of these compounds by talc and kaolin occurs through more complex mechanisms which cannot be completely elucidated from knowledge obtained in this experiment. The effects of pH and electrolyte concentration may be important to the previously observed action of adsorbents in modifying absorption of promazine from the gastrointestinal tract.
PREVIOUS publication (1) presented a partial
A report of results obtained in this experiment.
Various medicinally active phenothiazinc derivatives were found to be adsorbed to a significant extent by kaolin, talc, and activated charcoal. The purpose of this report is to describc various aspects of the adsorption process in further detail and to present results of studies concerned with attempts to elucidate the mechanisms of the adsorption interaction. In addition, there is interest in adsorption as a potential mcans of altering drug absorption from the gastrointestinal tract (2, 3). Certain factors have been studied for their ability to produce release of the absorbed material from the surface of the adsorbate coinplex. In viwo experiments have involved the use of promazine hydrochloride, Thus, several experiments reported here feature this cornpound.
Results obtained for promazine hydrochloride should be qualitatively similar for other phenothiazine derivatives.
EXPERIMENTAL
Preparation of Compounds for Study.--The phenothiazine derivatives uscd in this study wcrc obtained from various sources of supply.' Each