AAPS PharmSciTech

, Volume 9, Issue 1, pp 302–313 | Cite as

Controlled Release Matrix Tablets of Zidovudine: Effect of Formulation Variables on the In Vitro Drug Release Kinetics

  • Punna Rao Ravi
  • Udaya Kanth Kotreka
  • Ranendra Narayan Saha
Research Article/Themed Issue: Oral Controlled Release Development and Technology/Guest Editors: Stephen Howard and Jian-Xin Li


The purpose of this research was to design oral controlled release (CR) matrix tablets of zidovudine (AZT) using hydroxypropyl methylcellulose (HPMC), ethyl cellulose (EC) and carbopol-971P (CP) and to study the effect of various formulation factors on in vitro drug release. Release studies were carried out using USP type 1 apparatus in 900 ml of dissolution media. Release kinetics were analyzed using zero-order, Higuchi’s square root and Ritger–Peppas’ empirical equations. Release rate decreased with increase in polymer proportion and compression force. The release rate was lesser in formulations prepared using CP (20%) as compared to HPMC (20%) as compared to EC (20%). No significant difference was observed in the effect of pH of dissolution media on drug release from formulations prepared using HPMC or EC, but significant difference was observed in CP based formulations. Decrease in agitation speed from 100 to 50 rpm decreased release rate from HPMC and CP formulations but no significant difference was observed in EC formulations. Mechanism of release was found to be dependent predominantly on diffusion of drug through the matrix than polymer relaxation incase of HPMC and EC formulations, while polymer relaxation had a dominating influence on drug release than diffusion incase of CP formulations. Designed CR tablets with pH independent drug release characteristics and an initial release of 17–25% in first hour and extending the release up to 16–20 h, can overcome the disadvantages associated with conventional tablets of AZT.

Key words

controlled release matrix tablets release kinetics zidovudine 



The authors are grateful to Strides Arcolab Limited, Bangalore, India, for generous gift samples of AZT and IPCA laboratories, Mumbai, India, for providing gift samples of HPMC, EC and CP. The authors wish to thank University Grants Commission, New Delhi, India, for funding the project.


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Copyright information

© American Association of Pharmaceutical Scientists 2007

Authors and Affiliations

  • Punna Rao Ravi
    • 1
  • Udaya Kanth Kotreka
    • 1
  • Ranendra Narayan Saha
    • 1
  1. 1.Pharmacy GroupBirla Institute of Technology and SciencePilaniIndia

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