Polymorphism of paracetamol: A comparative study on commercial paracetamol samples.

Abstract

Paracetamol (acetaminophen) is an important analgesic and antipyretic drug which is used worldwide. Paracetamol shows polymorphism and exists in three forms. These are monoclinic (Form I, stable), orthorhombic (Form II, metastable) and Form III (unstable and not yet characterized). Most of the paracetamol drug samples belong to monoclinic form which is the most stable polymorph. Paracetamol is prepared by the reaction between 4-aminophenol and ethanoic anhydride and is purified. The product obtained is characterized by melting point and spectral techniques like IR and UV-Visible spectroscopy. Various commercial paracetamol tablets were collected, powdered and their melting points were determined. All the eleven drug samples analyzed are found to be belonging to the stable monoclinic form.