Preparation and evaluation of sustained release carbamazepine matrix tablets using Eudragit RS 100 and Tragacanth

Carbamazepine is a widely prescribed anticonvulsant antiepileptic drug which shows variable absorption and variable bioavailability.  It is advisable to prep. it in sustained release dosage form to improve patient compliance and to perform const. blood level with min. side effects.  Problems may be encountered with carbamazepine tablets prepd. by wet granulation if the granules are not thoroughly dried before processing.  Therefore, the present study deals with the application of direct compression technique to prep. sustained release carbamazepine matrix tablets.  Different levels (0 to 25 % wt.​/wt.) of Eudragit RS 100 and Tragacanth were tested to select the best level of matrix forming material that provides the most release prolonging effect, by direct compression technique using Avicel PH 102 and anhyd. lactose as directly compressible vehicles.  Directly compressed matrix tablets of carbamazepine were found to be complied with the USP​/NF 23 requirements for the uniformity of wt., diam., and acceptable mech. properties with respect to tensile strength and friability.  Examn. of the release characteristics of the drug from the directly compressed tablets as well as the detn. of the release mechanism were carried out.  It was found that, as the percentage of the polymer (either Eudragit or Tragacanth) in all formulations increased from 3.125​% to 18.75​% or 25​% wt.​/wt., the drug release decreased significantly.  Involvement of Eudragit RS 100 in the directly compressed matrix tablets gave more sustaining release of carbamazepine than inclusion of Tragacanth in both acidic medium (pH 1.2) and phosphate buffer medium (pH 6.8)​.  This was due to the difference between the physicochem. properties of natural polymer Tragacanth and synthetic polymer Eudragit.  Comparatively, the formula of carbamazepine tablet contg. 25 % wt.​/wt. Tragacanth showed similar release behavior to that of the com. Tegretol tablets.  The calcd. exponential release exponents (n values) indicated that release behavior of carbamazepine matrix tablets was anomalous (non-​Fickian) diffusion kinetics.