Abstract
Celecoxib is a selective COX-2 inhibitor non-steroidal anti-inflammatory drug (NSAID) used in the treatment of osteoarthritis, rheumatoid arthritis, and to reduce numbers of colon and rectum polyps in patients with familial adenomatous polyposis. Celecoxib is practically inslouble in GIT pH. Consequently, it suffers from low and variable bioavailability following oral administration of solutions (64-88%) and capsules (20-40%) In the present study, gastroretentive controlled release single-unit floating capsules of Celecoxib were designed and evaluated. Various grades of low and high viscosity polymers of HPMC 4000 and 15.000 cps and NaCMC were used for formulation of Celecoxib capsules. For the purpose of enhancing the poor dissolution rate of Celecoxib, co-adsorption with Tween 80 onto surface of Florite® was investigated in this study. Thus, controlled release limited by drug solubility was percluded and delivery of active material was controlled by the formulation. In the present study conventional capsules containing Celecoxib using HPMC and NaCMC were developed and evaluated. Floating capsules containing Celecoxib, co-adsorption with Tween 80 onto surface of Florite and Aerosil 200 in different ratios were also formulated and investigated for the release of the drug from these capsules. The results obtained of this study showed that Celecoxib capsules containing HPMC 15000cps as a swelling matrix has a good floating behaviour and retarding effect on the drug release. Also, different concentrations of sodium bicarbonate confirmed and maintained the floating properties of the prepared formulations without affecting the drug release. From DSC and X-ray diffraction studies it was found that crystalline Celecoxib was converted into the amorphous form in the presence of Florite® at (1:5 w/w drug: carrier ratio) in the adsorbate and co-adsorbate with Tween 80. The loaded and ground mixtures of Celecoxib with either Florite® or Aerosil 200 increased the dissolution rate of the drug. Furthermore, co-adsorbate of the drug with Florite® and Tween 80 at these ratios of (1:5:3 and 1:5:5) gave the highest percentage released of Celecoxib (reached about 100% at 30 and 45 min., respectively).
Highlights
For the past three decades, oral controlled release dosage forms have been developed due to their important therapeutic advantages
The results obtained of this study showed that Celecoxib capsules containing HPMC 15000cps as a swelling matrix has a good floating behaviour and retarding effect on the drug release
Besides being able to continually and sustainedly deliver drugs to the small intestinal absorption window, the improvements provided from gastroretentive drug delivery systems (GRDDSs) include: achieving a greater and prolonged therapeutic effect and reducing the frequency of administration periods, providing a more effective treatment of local stomach disorders, and minimizing both lowertract inactivation of the drug and drug effects on the lower intestinal flora (Berner and Louie- Helm, 2002; Shell et al, 2003)
Summary
For the past three decades, oral controlled release dosage forms have been developed due to their important therapeutic advantages. By the introduction of a variety of controlled delivery systems, the inconvenience of conventional tablets or capsules that resulted in a transient overdose, followed by a long period of dosing was overcome One of these delivery systems is the gastroretentive drug delivery systems (GRDDSs). Recent improvements in the field of size-increasing (swelling/expanding) drug delivery systems led to devices that caneasily be swallowed but rapidly increase in size once they reach the stomach, assuring prolonged gastric residence times. Their performance is independent of the filling state of the stomach and, after predetermined time intervals, they break into smaller pieces, guaranteeing their removal from the stomach. Floating and bioadhesion to achieve retention have been combined in tablets consisting of blends of HPMC and Carbopol (Nur and Zhang, 2000) and tablets containing sotalol HCl, sodium carboxymethyl cellulose (as the bioadhesive polymer), HPC (as the matrix-forming polymer), and carbonate (as the gas generator) (Jiménez-Castellanos et al, 1994)
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