A new generation starch product as excipient in pharmaceutical tablets. III. Parameters affecting controlled drug release from tablets based on high surface area retrograded pregelatinized potato starch.

This paper describes the general applicability of a new pregelatinized starch product in directly compressible controlled-release matrix systems. It was prepared by enzymatic degradation of potato starch followed by precipitation (retrogradation), filtration and washing with ethanol. The advantages of the material include ease of tablet preparation, the potential of a constant release rate (zero-order) for an extended period of time and the possibility to incorporate high percentages of drugs with different physicochemical properties. Constant release profiles are the result of solvent penetration into the tablet. For theophylline as test drug, constant release profiles could be realized up to a drug content of 75%. This illustrates the possibility to control the release of highly dosed drugs. Release rates from retrograded pregelatinized starch tablets can be enhanced or decreased to the desired profile by different parameters, like geometries of the tablet, compaction force and the incorporation of additional excipients. For procaine HCl it is demonstrated that larger tablets show slower release rates. The incorporation of soluble excipients like lactose and mannitol results for paracetamol in enhanced release rates. The delivery of bases and their salts can be modified by the incorporation of organic acid or alkaline excipients, as is demonstrated for lidocaine and procaine HCl.