title: Additive-induced metastable single crystal of mefenamic acid.
abstract: OBJECTIVE
  To utilize additives to develop a strategy and a method to grow single crystals that allow structure determination of a metastable form of a drug.
  
  
  METHODS
  The metastable form of mefenamic acid (MFA) was grown in the presence of various amounts of the structurally similar additive flufenamic acid (FFA) in ethanol. Single crystal X-ray analysis was performed on the single crystals of MFA II that were formed. The solubility of MFA in the presence of FFA was measured to elucidate the mechanism of MFA II formation.
  
  
  RESULTS
  A supersaturated solution of MFA in ethanol produced the metastable form using FFA as an additive. Ethanol-water mixtures and toluene were also used to investigate the relationships between form produced and solvent since these two solvent systems do not produce MFA II.
  
  
  CONCLUSIONS
  Additives can be used to obtain the metastable form of pharmaceutical compounds, and the relationships between molecules and solvent as well as between host and guest molecules are critical to obtaining the desired form.
authors.affiliation: Department of Industrial and Physical Pharmacy, Purdue University, 575 Stadium Mall Drive, West Lafayette, Indiana 47907, USA.
authors.forename: Eun Hee
authors.initials: EH
authors.lastname: Lee
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Byrn
authors.forename: M Teresa
authors.initials: MT
authors.lastname: Carvajal
mesh_terms: D002851:Chromatography, High Pressure Liquid; D003460:Crystallization; D005439:Flufenamic Acid / Q000737:chemistry; D008528:Mefenamic Acid / Q000737:chemistry*; D008958:Models, Molecular; D012995:Solubility; D014961:X-Ray Diffraction
chemical_list: D008528:Mefenamic Acid; D005439:Flufenamic Acid