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

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 DE8% (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 DE8%. 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.