Abstract: OBJECTIVE To prepare clenbuterol hydrochloride sustained-release bilayer tablets and study its pharmaceutical characteristics in vivo and in vitro. METHODS HPMC and EC mixed matrix were used to prepare clenbuterol hydrochloride sustained-release bilayer tablets by direct compression technique and wet granulation technique. The release characteristics in vitro and pharmacokinetics in dogs of clenbuterol hydrochloride sustained-release bilayer tablets were investigated.RESULTS The drug dissolution of sustained-release bilayer tablets was consistent with Higuchi equation. The peak levels (Cmax) after administration of sustained-release bilayer tablets and reference tablets were (5.86±0.33) and (11.43±0.64) ng·mL-1 at (3.17±0.73) and (2.02±0.35) h, respectively. The mean elimination half lives (t1/2) were found to be (11.90±1.42) and (6.18±0.81) h, respectively. AUC0-t were calculated to be (65.08±2.63) and (68.00±2.89) ng·h·mL-1, respectively.CONCLUSION The clenbuterol hydrochloride sustained-release bilayer tablets exhibited both sustained-and rapid-release characteristics in vitro. The calculated MRT of sustained-release bilayer tablets was significantly more than that of reference tablets. There existed correlation between thein vitro release and in vivo absorption.