DARU Journal of Pharmaceutical Sciences 2008. 16(3):136-142.

pH-independent release of propranolol hydrochloride from HPMC-based matrices using organic acids


Background and purpose of the study: Propranolol HCl, a widely used drug in the treatment of cardiac arrhythmias and hypertension, is a weak basic drug with pH-dependent solubility that may show release problems from sustained release dosage forms at higher pH of small intestine. This might decrease drug bioavailability and cause variable oral absorption. Preparation of a sustained release matrix system with a pH-independent release profile was the aim of the present study.

Methods: Three types of organic acids namely tartaric, citric and fumaric acid in the concentrations of 5, 10 and 15 % were added to the matrices prepared by hydroxypropyl methylcellulose (HPMC) and dicalcium phosphate. The drug release studies were carried out at pH 1.2 and pH 6.8 separately and mean dissolution time (MDT) as well as similarity factor (¦2) were calculated for all formulations.

Results and discussion: It was found that incorporation of 5 and 10 % tartaric acid in tablet formulations with 30 % HPMC resulted in a suitable pH-independent release profiles with significant higher ¦2 values (89.9 and 87.6 respectively) compared to acid free tablet (58.03). The other two acids did not show the desirable effects. It seems that lower pKa of tartaric acid accompanied by its higher solubility were the main factors in the achievement of pH-independent release profiles.


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