A Comparative Study of Modified Starches in Direct Compression Tabletting

Abstract

Starches have traditionally been used in the pharmaceutical industry as filler, binder and disintegrant. Pharmaceutical grade starches are derived mainly from maize grains and potato tubers. Current advances in tableting technology, especially the use of high-speed, multi-station rotary tablet press, and direct compression tableting techniques, have necessitated the use of excipients with good flow and compression characteristics. Some pharmaceutical grade starches are therefore modified to meet the flow and compression requirement for direct compression tableting. In Nigeria, there are abundant sources of starch. The processing technique for pharmaceutical grades starch is not far-fetched. Yet Nigeria imports all its starch requirement for drug production. This work was designed to establish a simple and effective technique for the derivation of pharmaceutical grade direct compression starch. The technique in view should be amenable to industrial application. It was also desired to establish any inherent differences between starches from the different sculenta, ource studied. The sources were maize, Zea mays; rice, Oryza sativa, cassava, Manihot esculenta and cocoyam, Xanthosoma sagittifolium. Extraction of starches was essentially by the wet-milling process. Modification involved heat and acid treatment. The flow and compression characteristics of the modified starches were evaluated. Star-X 1500, a commercial grade of direct compression starch was used as basis for comparison. The starches were used in the formulation of directly compressed ascorbic acid, hydrochloro thiazide and chloriquine phosphate tablets. These formulations are examples of high dose, poorly compressible, low dose, poorly soluble and high dose soluble tablet formulations respectively. Tablet properties evaluated included weight and drug content uniformity, hardness, friability, disintegration time and dissolution rate. The wet-milling process of starch extraction yielded white starch granules. The heat and acid treatment yielded products with excellent direct compression characteristics. The starch samples exhibited species speficity in terms of individual powder properties and the characteristics of tablets compressed from them. The modified starches may be ranked in order of increasing flowability as modified rice> cassava> cocoyam starch. The ranking on the basis of high compressibility is modified rice> cassava> maize> cocoyam starch. The hydrochlorothiazide and ascorbic acid tablets formulated with the modified starches met Pharmacopoeial requirements for weight uniformity, disintegration time and dissolution of such tablets. It was not possible to produce good chloroquine phosphate tablets by diredtion compression with the modified starches. This was attributed to the high dose nature of this drug.