title: [Studies on the solubility and the distribution behaviour of butaperazine dihydrogen maleate (author's transl)].
abstract: The present paper deals with the study of those parameters of butaperazine dihydrogen maleate, the knowledge of which is of importance in planning dosage forms for oral use. The solubility of the free butaperazine base in artificial intestinal juice (2.03 mg / 100 ml) was determined by means of the pKa values (pKa = 3.58 and pKa = 8.14). The total solubility decreases as the pH value of the dissolving medium increases, because the concentration of the base limits the solubility of the drug. Only the base can be distributed between n-heptane and an aqueous phase. The actual distribution coefficients are very high and explain the high solubility in fat. The water-lipid transfer was also estimated quantitatively. The highest velocities of transfer were observed at a pH value somewhat less than 7.0, as it is commonly measured in the small intestine. At pH 8.0, the low solubility of butaperazine became the velocity-limiting factor of the transfer. The velocities of the back transfer suggest that it is not wise to study the distribution behaviour of butaperazine in a three-phase model if the transfer at a buffer pH 7.4 is the centre of interest.
mesh_terms: D005750:Gastric Juice / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007419:Intestinal Secretions / Q000378:metabolism; D007700:Kinetics; D008055:Lipids; D008954:Models, Biological; D010640:Phenothiazines / Q000378:metabolism*; D012995:Solubility; D014867:Water
chemical_list: D008055:Lipids; D010640:Phenothiazines; D014867:Water
vernacular_title: Untersuchungen zur Löslichkeit und dem Verteilungsverhalten von Butaperazindibimaleinat.