title: Dissolution studies on ampicillin embonate and amoxycillin embonate.
abstract: The dissolution behaviour of slightly water-soluble embonic acid salts of ampicillin and amoxycillin was studied quantitatively as a function of solution pH (1.15-8.00) using the rotating disk method combined with reversed-phase high-performance liquid chromatography. The dissolution rate of ampicillin embonate was greater than that of amoxycillin embonate at all pH values investigated. The graphs of pH-intrinsic rate of dissolution of the antibiotics from the salts were U-shaped, the minimum being close to the respective isoelectric points of the parent antibiotics. Embonic acid was not detectable below pH 5; above pH 5 the dissolution rate of embonic acid increased as a function of pH.
authors.affiliation: Division of Pharmaceutical Chemistry, University of Helsinki, Finland.
authors.forename: T
authors.initials: T
authors.lastname: Saesmaa
authors.forename: A M
authors.initials: AM
authors.lastname: Tötterman
mesh_terms: D000658:Amoxicillin / Q000737:chemistry*; D000667:Ampicillin / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009284:Naphthols / Q000737:chemistry; D012995:Solubility
chemical_list: D009284:Naphthols; D000667:Ampicillin; C004368:pamoic acid; D000658:Amoxicillin