title: [The solubility of drugs in molten suppository bases].
abstract: Solubility of 18 drugs used in rectal therapy in molten suppository base, (Massa suppositoriorum 15, Pharmacopeia of the G.D.R. Rosupol U, 37 degrees C) is determined. Separation of drug-saturated base from drug cristals is carried out in an air-heated centrifuge followed by a partition step between petroleum ether and an aqueous medium and photometrical determination of drug concentration. The procedure leads to results with relative standard deviation of 2% (medium value of 18 drugs). The investigation gave solubility values in the range between 0.002% (theobromine) and 26% (lidocaine), whereas benzoate, phenobarbital sodium and procaine hydrochloride are completely insoluble. Sodium salicylate has an unexpected high solubility (0.48%). The solubility is temperature depended and thus the solubility enthalpy can be determined. Relations between structure and solubility are discussed for pyrazolin-5-ones and purines. A correlation between solubilities in the base and in aqueous buffer (phosphate, pH 7.4) does not exist in the series studied.
authors.affiliation: Sektion Pharmazie, Ernst-Moritz-Arndt-Universität Greifswald.
authors.forename: P
authors.initials: P
authors.lastname: Pflegel
authors.forename: H
authors.initials: H
authors.lastname: Schöbel
authors.forename: T
authors.initials: T
authors.lastname: Klaus
authors.forename: U
authors.initials: U
authors.lastname: Raguse
mesh_terms: D002626:Chemistry, Pharmaceutical; D005079:Excipients; D004364:Pharmaceutical Preparations / Q000032:analysis*; D010783:Photometry; D012995:Solubility; D013488:Suppositories; D013696:Temperature; D013816:Thermodynamics
chemical_list: D005079:Excipients; D004364:Pharmaceutical Preparations; D013488:Suppositories
vernacular_title: Löslichkeit von Arzneistoffen in geschmolzener Suppositorienmasse.