Evaluation of natural and pregelatinized forms of three tropical starches as excipients in tramadol tablet formulation

Abstract

In the present study, tropical starches from three botanical sources, namely millet starch obtained from the grains of Pennistum glaucum (L) R Br (family Poaceae), sorghum starch from the grains of Sorghum bicolor L. Moench (family Gramineae) and cocoyam starch from the tubers of Colocasia esculenta (L) Schott (family Araceae), have been modified and evaluated as directly compressible excipients in tramadol tablet formulations. The starches were extracted from the relevant plant parts, modified by pregelatinization followed freeze-drying and used as directly compressible excipients in tramadol tablets, and the tablet properties compared with those made with the natural forms of the starches. The results indicate that starches from the three botanical sources vary in their properties and pregelatinization led to the modification of the physicochemical and material properties of the starches. The pregelatinized starches exhibited better flowability and compressibility than the natural starches. Tramadol tablets prepared with freeze-dried pregelatinized starches generally exhibited higher crushing strength but lower friability than those prepared with the natural starches. The rankings of the crushing strength and the disintegration and dissolution times was cocoyam > millet > sorghum starches, with tramadol tablets containing freeze-dried pregelatinized starches exhibiting significantly (p < 0.01) higher disintegration and dissolution times than tablets made with the natural forms of starches. The freeze-dried pregelatinized starches were suitable as directly compressible excipients and provided controlled release of tramadol indicating their potential application in formulations where slower drug release is desired.