1458

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The present study was proposed to formulate an oral delivery device, in the form of a bi-layer tablet in which first layer is formulated to obtain a prompt release of one drug i.e. hydrochlorothiazide, with the aim of reaching a high serum concentration in a short period of time. The second layer is a prolonged-release hydrophilic matrix containing another drug i.e. captopril, which is designed to maintain an effective plasma level for a prolonged period of time. The immediate release layer and sustained release layer was optimized separately and then constituted in bilayer tablet. Different viscosity grades of HPMC (i.e. HPMC K4M, K15M, and K100M), Xanthan gum and combination of HPMC and Xanthan gum were used as matrix forming material for sustaining release of captopril. Sustained release layer was optimized by swelling studies and dissolution studies of prepared matrices. Drug release from tablets containing Xanthan gum was slightly faster as compared to HPMC formulations. In case of HPMC matrix tablet the drug release depends on concentration and viscosity grade of polymer used. Immediate release layer was formulated using different concentration of disintegrants like Croscarmellose sodium and Crospovidone. Disintegration time and drug release were taken as the basis to optimize the immediate release layer. Crospovidone in the concentration of 4 % gives fasted disintegration in 13 sec. Bilayer tablet was prepared from optimized formulation of immediate and sustained release layer. Prepared bilayer tablet formulations were subjected to stability studies for thirty days which showed stability with regards to release pattern.
Keywords: Bilayer tablet; Matrix tablet; HPMC; Xanthan gum; Direct compression.

INTRODUCTION
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...d hydrochlorothiazide combination therapy may include improved compliance and synergistic reductions in blood pressure with an accomplished reduction in side effects10.
On the basis of these considerations, in the present study it was proposed to formulate an oral delivery device, in the form of a bi-layer tablet in which first layer was formulated to obtain a prompt release of hydrochlorothiazide, with the aim of reaching a high serum concentration in a short period of time. The second layer was a prolonged-release hydrophilic matrix containing captopril, which was designed to maintain an effective plasma level for a prolonged period of time. The combination of a fast release pulse with a slow release pattern could allow for an easier and more flexible optimization of the fast and slow dose fractions as a function of the pharmacokinetics and metabolism of the drug.

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