title: A new method of producing monoclinic paracetamol suitable for direct compression.
abstract: OBJECTIVE
  To develop a technique of obtaining monoclinic polymorph of paracetamol suitable for direct compression without excipients.
  
  
  METHODS
  Preparation of spongy monoclinic paracetamol was based on quench-cooling of paracetamol solutions in water-acetone mixtures sprayed into a vessel with liquid nitrogen followed by removal of solvents by freeze-drying. X-ray powder diffraction was used to study annealing of quench-cooled solutions in "paracetamol-acetone-water" and "acetone-water" systems and to find optimum conditions for obtaining fine particles of pure monoclinic paracetamol. Samples were characterized by electron microscopy; compression properties were measured.
  
  
  RESULTS
  The preparation technique gave fine monoclinic paracetamol powder containing agglomerates (30-200 μm) composed of flat particles (linear sizes 1-10 μm, the thickness 60-150 nm). The spongy sample was suitable for direct compression without excipients, stable on storage, and mechanically robust. Mechanically stable tablets pressed from the spongy sample were better soluble in water than commercially available tablets of paracetamol with excipients.
  
  
  CONCLUSIONS
  The proposed method gave spongy monoclinic paracetamol samples with improved properties. For inexpensive paracetamol, the method may not yield economic advantage. However, the same method based on freeze-drying solutions in mixed aqueous-organic solvents can be used to prepare new improved forms of other molecular solids for pharmaceutical applications.
authors.affiliation: REC-008 "Molecular Design and Ecologically Safe Technologies", Novosibirsk State University, ul. Pirogova 2, Novosibirsk 630090, Russia.
authors.forename: Andrey G
authors.initials: AG
authors.lastname: Ogienko
authors.forename: Elena V
authors.initials: EV
authors.lastname: Boldyreva
authors.forename: Andrey
authors.initials: A
authors.lastname: Yu Manakov
authors.forename: Vladimir V
authors.initials: VV
authors.lastname: Boldyrev
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Yunoshev
authors.forename: Anna A
authors.initials: AA
authors.lastname: Ogienko
authors.forename: Svetlana A
authors.initials: SA
authors.lastname: Myz
authors.forename: Alexei I
authors.initials: AI
authors.lastname: Ancharov
authors.forename: Andrey F
authors.initials: AF
authors.lastname: Achkasov
authors.forename: Tatiana N
authors.initials: TN
authors.lastname: Drebushchak
mesh_terms: D000082:Acetaminophen / Q000737:chemistry*; D000096:Acetone / Q000737:chemistry; D018712:Analgesics, Non-Narcotic / Q000737:chemistry*; D002626:Chemistry, Pharmaceutical / Q000379:methods*; D005612:Freeze Drying; D016062:Porosity; D033362:Powder Diffraction; D012997:Solvents / Q000737:chemistry; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D018712:Analgesics, Non-Narcotic; D012997:Solvents; D014867:Water; D000096:Acetone; D000082:Acetaminophen