Sustained release drug system is any drug or dosage form modification that prolongs the therapeutic activity of the drug. Ideally a sustained release oral dosage form is designed to release rapidly some predetermined fraction of the total dose in to GI tract. This fraction (loading dose) is an amount of drug, which will produce the desired pharmacological response as promptly as possible and the remaining fraction of the total dose (maintenance dose) is then release at a constant rate. The rate of the drug absorption from the entire maintenance dose into the body should equal to the rate of the drug removal from the body by all the processes over the time for which the desired intensity of pharmacological response is required. We sincerely hope that this book will helpful to student as well as industry and academic professionals involved in pharmaceutical and other related science.

Novel drug delivery systems (NDDS) have recently gained importance for delivering a variety of therapeutic agents for both local and systemic administration. Delivery of drugs directly to targeted sites of action provides several advantages over non-specific delivery of drugs. Oral colon targeted drug delivery system is one of that NDDS which directly deliver a drug in to the colon for local treatment of a variety of colonic diseases as well as systemic absorption of proteins and peptides. The Metronidazole is the drug of choice in the treatment of the diseases like Amoebiasis, Giardiasis, Trichomonosis and Bacterial Vaginosis. The aim of the present research was to design, development and optimization of swellable rupturable system taking account of local action of the Metronidazole drug in the lower gastrointestinal tract to kill the bacteria in the disease conditions like Amoebiasis, Giardiasis and Trichomonosis.