Preparations of agglomerated crystals of polymorphic mixtures and a new complex of indomethacin-epirizole by the spherical crystallization technique

Abstract

Agglomerated crystals of indomethacin and epirizole were prepared by the spherical crystallization technique. The solvent used was ethanol-water-chloroform, ethyl acetate-water, or ethyl acetate-aqueous sodium chloride. From the ethanol-chloroform-water system, we obtained agglomerated crystals of a polymorphic mixture of the beta form of indomethacin (original form, gamma) and amorphous epirizole. When the mole percent of epirizole loaded into the system was less than 63 and 38% for the ethyl acetate-water and ethyl acetate-aqueous sodium chloride systems, respectively, the agglomerated crystals consisted of a polymorphic mixture of the alpha form of indomethacin and amorphous epirizole. When the respective mole percent of epirizole loaded was more than 65 and 43% in the aforementioned systems, a new complex of indomethacin-epirizole (molecular ratio equal to 2:1) was obtained. Recovery of complex from the drugs loaded in the ethyl acetate-aqueous sodium chloride system was higher than that in the ethyl acetate-water system, as a result of a salting-out effect. The solubility of indomethacin in the agglomerated complex in a solution of 30% aqueous ethanol and in disintegration test solution no. 2 (composition, 0.05 M KH2PO4 plus 0.0236 M, NaOH, pH 6.8), specified in the Japanese Pharmacopeia X (JPX), was higher than in the physical mixture (molecular ratio of indomethacin to epirizole equal to 2:1). In the ethanol solution, indomethacin was transformed into the gamma form during dissolution, and a decrease in solubility occurred. The process of dissolution of the tablet of the agglomerated complex was described by zero-order kinetics.(ABSTRACT TRUNCATED AT 250 WORDS)