Comparison of hydrophilic natural gums and cellulosic polymers in formulation of sustained-release matrix tablets of terbutalin sulfate

Abstract

The short half-life of terbutaline sulphate (TBS) requires frequent dosing for controlling chronic pulmanary disorders, such as night asthma. The purpose of the present study was to prepare sustained-release (SR) tablets of TBS to decrease the number of doses frequency and to promote the paitent compliances. It was also desirable to evaluate the capability of natural gums for preparation of SR oral dosage forms in comparison with the cellulosic polymers. SR tablets of TBS (7.5 mg) were prepared using either natural gums; Guar (G) or Xanthan (X) and cellulosic polymers; hydroxypropyl methylcellulose (H) or carboxymethyl cellulose (C) by direct compression method. Different ratios of 0:100, 20:80, 40:60, 60:40 of C : H, G : X, X : H or H : G were used. After evaluation of physical characteristics of tablets, release rate were compared with the standard tablets (Bricanyl^® SR) in phosphate buffer solution (pH 7.4). All tablets met the official physical properties. Tablets with 80:20 ratio of polymers, H₈X₂ and G₈X₂ had smaller DE_8% (Dissolution Efficiency) and higher MDT (Mean Dissolution Time)_.  In the ratio of 60:40 and 40:60 formulations H₄X₆ and H₆X₄ had the highest MDT, and the smallets DE_8%. Formulation H₄X₆ released the drug with zero-order kinetics while H₆X₄ followed a Higuchi pattern such as standard tablet. It is concluded that formulation containing Guar and Xanthan (G₈X₂) released the drug with a zero-order kinetic and was the most similar formulation to the standard.