title: Colon Cancer and Specific Ways to Deliver Drugs to the Large Intestine.
abstract: BACKGROUND
  It has been postulated that colon cancer is the third cause of cancer death worldwide. Recently, colon-targeted drug delivery systems have been developed for improving systemic drug delivery and treatment of local colon associated diseases. Using such drug delivery systems increases the drug's effectiveness and results in reduced systemic side effects. Drug delivery systems formulated for the colon requires that the triggering of drug release mechanism is designed based on the colon's physiological conditions. However, improving the site specificity and drug release kinetics of colon-targeted drug delivery systems is desired and is currently under active research.
  
  
  OBJECTIVE
  This review discusses colon cancer along with various colon-targeted drug delivery systems such as pro-drug formation, pH-sensitive polymers, hydrogels, time-dependent release systems, bio-adhesive and nanoparticle systems. The aim is to understand the effect of using colon-targeted drug delivery systems on therapeutic effectiveness of the drug by improving its degradation and bioavailability. Colon targeting holds a great promise as a therapeutic approach but it still requires more innovation.
  
  
  CONCLUSIONS
  The distribution of the drugs in the colon suffers from problems related to the pH, retention time, micro-flora, and degrading enzymes of gastrointestinal tract. Moreover, these drug delivery systems are capable of overcoming some of the limitations in common targeting approaches. A precise assessment of such systems needs the use of various assaying protocols in order to characterize their traits and clarify their design rationales.
authors.affiliation: Department of Pharmaceutical Biomaterials and Medical Biomaterials Research Centre, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran. Iran.
authors.forename: Hossein
authors.initials: H
authors.lastname: Derakhshankhah
authors.affiliation: Department of Pharmaceutical Biomaterials and Medical Biomaterials Research Centre, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran. Iran.
authors.forename: Zhila
authors.initials: Z
authors.lastname: Izadi
authors.affiliation: Institute of Biochemistry and Biophysics, University of Tehran, Tehran. Iran.
authors.forename: Loghman
authors.initials: L
authors.lastname: Alaei
authors.affiliation: Department of Pharmaceutical Biomaterials and Medical Biomaterials Research Centre, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran. Iran.
authors.forename: Alireza
authors.initials: A
authors.lastname: Lotfabadi
authors.affiliation: Institute of Biochemistry and Biophysics, University of Tehran, Tehran. Iran.
authors.forename: Ali Akbar
authors.initials: AA
authors.lastname: Saboury
authors.affiliation: Department of Pharmaceutical Biomaterials and Medical Biomaterials Research Centre, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran. Iran.
authors.forename: Rassoul
authors.initials: R
authors.lastname: Dinarvand
authors.affiliation: Department of Biological Sciences, Kharazmi University, Tehran. Iran.
authors.forename: Adeleh
authors.initials: A
authors.lastname: Divsalar
authors.affiliation: Institute of Biochemistry and Biophysics, University of Tehran, Tehran. Iran.
authors.forename: Arefeh
authors.initials: A
authors.lastname: Seyedarabi
authors.affiliation: Institute of Biochemistry and Biophysics, University of Tehran, Tehran. Iran.
authors.forename: Ebrahim
authors.initials: E
authors.lastname: Barzegari
authors.affiliation: Institute of Biochemistry and Biophysics, University of Tehran, Tehran. Iran.
authors.forename: Mina
authors.initials: M
authors.lastname: Evini
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D003110:Colonic Neoplasms / Q000188:drug therapy*; D004305:Dose-Response Relationship, Drug; D016503:Drug Delivery Systems; D004354:Drug Screening Assays, Antitumor; D006801:Humans; D007420:Intestine, Large / Q000187:drug effects*; D015394:Molecular Structure; D011355:Prodrugs / Q000494:pharmacology*; D013329:Structure-Activity Relationship
chemical_list: D000970:Antineoplastic Agents; D011355:Prodrugs
keywords: Colon drug delivery system; colon cancer; colonic drug
  absorption; colonic floral enzymes; colonic micro-flora; targeted drug release