A new method for obtaining fine powders of paracetamol for compression without excipients

Paracetamol (N(phydroxyphenyl)acetamide) is a widely used nonnarcotic analgesic having also anti inflammatory and antipyretic action. Several crystalline polymorphs of paracetamol are known. One of these (monoclinic form I) is thermodynamically stable and is readily prepared but cannot be compressed to tablets without excipients (fillers). Another polymorph (orthorhombic form II) can be readily compressed to tablets without excipients [1, 2] and is better soluble but its formation as a pure phase is not reproducible, and, what is worse, it is metastable and is spontaneously converted to the monoclinic form on storage [1]. The idea of obtaining compressible forms of paracetamol that would be stable on storage attracts considerable attention of the scientific community and pharmaceutical companies. For solving this problem, it has been proposed to use, instead of pure paracetamol, its mixtures with polyvinylpyrrolidone [3], carbohydrates [4], chitosan and sodium alginate [5] or mixed crystals based on oxalic acid, naphthalene and other compounds [6] or the inclusion compounds with hydroxypropylβcyclodextrin [7].