AAPS PharmSciTech

, Volume 14, Issue 2, pp 870–879

Studies on Tolfenamic Acid–Chitosan Intermolecular Interactions: Effect of pH, Polymer Concentration and Molecular Weight

  • Sofia Ahmed
  • Muhammad Ali Sheraz
  • Ihtesham Ur Rehman
Research Article

DOI: 10.1208/s12249-013-9974-9

Cite this article as:
Ahmed, S., Sheraz, M.A. & Rehman, I.U. AAPS PharmSciTech (2013) 14: 870. doi:10.1208/s12249-013-9974-9

Abstract

Solid-state properties of tolfenamic acid (TA) and its complexes with chitosan (CT) have been studied. Effect of medium pH, molecular weight of polymer and its different concentrations on these TA–CT complexes were studied in detail. Low and medium molecular weight CT have been used in different ratios at pH ranging from 4 to 6 and freeze-drying technique has been employed to modify the appearance of crystalline TA. Physical properties of the formed complexes have been studied by employing X-ray diffraction, differential scanning calorimetry and scanning electron microscopy; chemical structure has been studied using Fourier transform infrared spectroscopy. The results showed that both forms of the polymer exhibited complete conversion in 1:8 ratio at pH 4, 1:4 at pH 5 and 1:1 at pH 6 indicating a marked effect of pH on drug–polymer complexation. The percent crystallinity calculations indicated low molecular weight CT slightly more effective than the other form. No changes in the complexes have been observed during the 12 week storage under controlled conditions. Both forms of CT at different pH values indicated retardation of recrystallization in TA during cooling of the melt from 1:1 ratios exhibiting formation of strong intermolecular hydrogen bonding between the drug and the polymer.

KEY WORDS

amorphous chitosan effect of pH and molecular weight freeze-drying recrystallization tolfenamic acid 

Copyright information

© American Association of Pharmaceutical Scientists 2013

Authors and Affiliations

  • Sofia Ahmed
    • 1
  • Muhammad Ali Sheraz
    • 1
  • Ihtesham Ur Rehman
    • 1
  1. 1.Department of Materials Science and Engineering, The Kroto Research InstituteUniversity of SheffieldSheffieldUK