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1 gastroretentive drug delivery systems

  1. 1. Presented By : Akash Aher (M.pharm -2nd semester) Guided by : Dr.G.S Asane (Dept. of pharmaceutics)
  2. 2. Contents  Introduction  Need of Gastric retention  Advantages  Limitation  Physiology of Stomach  Approaches of Gastric retention  Evaluation of GRDDS  Conclusion
  3. 3. Introduction  Oral drug administration has been the predominant route for drug delivery.  Gastric residence time is time which a drug resides in stomach.  Depends upon fluid and food intake.  GRDDS are designed to delay gastric emptying.
  4. 4. Gastro retention is done for:  Drugs that absorb from stomach ( Levodopa, Furosemide).  Acting locally in stomach (Antacids, Antiulcer and Enzymes).  Antibiotic therapy.  Poorly soluble at alkaline pH.( Diazepam, Salbutamol)  Degrade in colon. (Captopril, Ranitidine, Metronidazole)  Narrow window of absorption
  5. 5. Fig.no-1
  6. 6. Gastric retention is unsuitable for:  Drugs having limited acid solubility. (Phenytoin)  Instable in gastric conditions. ( Erythromycin)  Extensive first pass metabolism. Factors affecting gastric retention of dosage forms  Density  Size  Shape
  7. 7. Advantages  Improved drug absorption, because of increased GRT and more time spent by the dosage form at its absorption site.  Controlled delivery of drugs.  Minimizing mucosal irritation by releasing drugs slowly at a controlled rate.  Treatment of gastrointestinal disorders such as gastro- esophageal reflux, providing local action.  Ease of administration and better patient compliance.
  8. 8. Limitations-  Retention in the stomach is not desirable for drugs that cause gastric lesions (e.g. Non- steroidal anti-inflammatory drugs NSAIDs).  Drugs that are degraded in acidic environment of stomach (e.g. Insulin).  Drugs that undergo a significant first-pass metabolism (e.g. Nifedipine).  Drugs that have very limited acid solubility (e.g. Phenytoin).
  9. 9. Review of Stomach & GIT A tube about nine meters long that runs through the middle of the body from the mouth to the anus and includes ;  throat (pharynx),  esophagus,  stomach,  small intestine - duodenum - jejunum - ileum  large intestine . Fig.no-2
  10. 10. Gastrointestinal dynamics  These are the four motility phases within the stomach during fasting stage.  The dosage form should be capable of withstanding the housekeeping action of phase III.
  11. 11. Approaches for gastric retention  Floating drug delivery systems  Mucoadhesive systems  Swellable Systems  High density systems. Fig.no-3
  12. 12. Fig.no-4
  13. 13. Floating drug delivery systems  These are low density systems.  Have ability to float over gastric contents.  The drug is must have sufficient structure to form a cohesive gel barrier.  It must maintain an overall specific gravity lower than that of gastric contents (1.004 – 1.010).  eased from the system at desired rate.
  14. 14. Floating Techniques  Effervescent  Volatile liquid containing systems  Gas generating systems  Non-Effervescent  Colloidal gel barrier systems  Alginate beads  Hollow Microspheres  Microporous Compartment System
  15. 15. Effervescent systems 1.Gas generating systems  Effervescence is there.  Utilizes effervescent reactions between carbonate/bicarbonate salts and citric/tartaric acid.  CO2 is released in presence of H2O.  When tablet is put in beaker it will sink  2NaHCO3+C4H6O6 C4H4Na2O6+2CO2+2H2O  With production of gas it rises up and floats.
  16. 16. 2. Volatile liquid containing systems  Incorporates an inflatable chamber, which contains a liquid e.g. ether, cyclopentane, that gasifies at body temperature to cause the inflatation of the chamber in the stomach.  The device may also consist of a bioerodible plug made up of PVA, Polyethylene, etc. that gradually dissolves causing the inflatable chamber to release gas and collapse after a predetermined time to permit the spontaneous ejection of the inflatable systems from the stomach.  There systems are very less used as the gas generating systems are more safe.
  17. 17. Non-effervescent systems 1. Colloidal gel barrier systems  Such systems contains drug with gel forming hydrocolloids meant to remain buoyant on stomach contents.  These systems incorporate a high level of one or more gel forming highly Swellable cellulose type hydrocolloids. e.g.HEC, HPMC, NaCMC.  On coming in contact with gastric fluids forms a viscous core.  Incorporates H2O and entraps air.  Density of system falls below 1gm/cm3. Then it starts floating Fig.no-5
  18. 18. 2. Microporous membrane systems  Based on the encapsulation of drug reservoir inside a Microporous compartment.  The peripheral walls of the drug reservoir compartment are completely sealed to prevent any direct contact of the gastric mucosal surface with the undissolved drug.  In stomach the floatation chamber containing entrapped air causes the delivery system to float over the gastric contents.  Gastric fluid enters through the apertures, dissolves the drug, and carries the dissolve drug for absorption.
  19. 19. 3. Alginate beads  Spherical beads of approximately 2.5 mm in diameter can be prepared by dropping a sodium alginate solution in to aqueous solutions of calcium chloride, causing precipitation of calcium alginate.  Sodium alginate+ Calcium chloride Calcium alginate+ NaCl  The beads are then separated snap and frozen in liquid nitrogen, and freeze dried at -40°C for 24 hours, leading to the formation of porous system.  Maintain a floating force of over 12 hours.
  20. 20. 4. Hollow microspheres  Microballoons / hollow microspheres loaded with drugs are prepared by simple solvent evaporation method.  Commonly used polymers to develop these systems are polycarbonate, cellulose acetate, calcium alginate, Eudragit S, agar and pectin etc.  These systems have capacity to float on acidic dissolution media containing surfactant for about 12 hours invitro.
  21. 21. Cont… Fig.no-6
  22. 22. Mucoadhesive systems  Involves the use of bioadhesive polymers, which can adhere to the epithelial surface in the stomach.  Dosage form can stick to mucosal surface by following mechanisms: 1. The wetting theory 2. The diffusion theory 3. The absorption theory 4. The electron theory
  23. 23. Swellable systems  A dosage form in the stomach will withstand gastric transit if it bigger than pyloric sphincter, but should be small enough to be swallowed.  These systems swells many times its original size.  Cross linking should be optimum highly cross linked don’t swell.  Chitosan, HPMC, sodium starch glycolate, carbopol are used.  Diclofenac, Ciprofloxacin, Furosemide are reported with these systems.
  24. 24. Fig.no-7
  25. 25. High density systems  These have density greater than that of gastric fluids (1.4 g/cc).  Above 1.6g/cc is preferable, tend to withstand peristaltic movements of stomach.  Zinc oxide, Iron oxide, Titanium dioxide, barium sulfate are used as inert heavy core. Fig.no-8
  26. 26. Evaluation of GRDDS Floating drug delivery systems Floating time • Determined by using the USP dissolution apparatus containing 900 ml of 0.1 N HCL maintained at 37o C. • The time for which the dosage form floats is termed as the floating time. Specific Gravity / Density • Density can be determined by the displacement method using Benzene as displacement medium
  27. 27. Muco – Adhesion system  Measurement of either tensile or shear strength is the most commonly used invitro method to measure bioadhesion strength.  Measurement of tensile strength involves quantiting the force required to break the adhesion bond between the test polymer and model membrane.  The method typically uses modified balance or tensile tester
  28. 28. Bioadhesion strength measurement Force measuring device Upper jaw Polymer Lower jaw Membrane Fig.no-9
  29. 29. Swelling systems Weight gain and water uptake  Done by immersing the dosage in simulated gastric fluid at 37oC and determining these factors at regular intervals.  Dimensional changes can be measured in terms of increase in the tablet diameter or thickness with time.  Water uptake is measured in terms of %weight gain
  30. 30. WU = (Wt-Wo) X 100 Wo Where WU – Water uptake Wt weight of dosage form at time t Wo weight of dosage form initially
  31. 31. Commercial Gastroretentive Formulation
  32. 32. Conclusion Gastro retentive drug delivery systems are the most preferable systems in order to deliver the drugs which have a narrow absorption window near the gastric region. Now a days a number of drug delivery devices are being developed which aim at releasing the drug at gastric region. Even though these drug delivery systems have several advantages they also have disadvantages like their invitro – invivo correlation is very less.
  33. 33. References  Doshi S.M., Tank H.M., Gastro Retention – An Innovation over Conventional poorly Soluble Drugs : A review, International Journal of Pharmaceutical and chemcal Sciences, 2012;1(2):859-866.  S. P. Vyas, Roop K. Khar, CONTROLLED DRUG DELIVERY – Concepts & Advances, Vallabh Prakashan, page no. 196-217.  N. K. Jain, Progress in Controlled & Novel Drug Delivery Systems, 1st edition 2004, CBS Publishers, page no.76-97  Chien Yie W. “ Novel drug delivery systems”, Vol-50, 2nd ed, Marcel Dekker . Inc, New York. Pg No.164-177.
  34. 34. • Anand S. Surana & Rakhee K. Kotecha, “An overvew on various approaches to oral controlled drug delivery system via gastroretention” IJPSRR, Vol-2, May- June 2010. pp: 68-72 • Shweta A, Javed A, Alka A, Roop K, and Sanjula B. Floating drug delivery systems: a review. AAPS PharmSciTech. 2005;6 (3) Article 47. • Ecyclopedia of Pharmaceutical Technology. • International Journal of Research in Pharmaceutical and Biomedical Sciences ISSN: 2229-3701
  35. 35. • G. Chawla, P. Gupta, V. Koradia, A. K. Bansal, Pharmaceutical Technology July 2003, 50-68 • Arora Shweta, Ali Javed, Ahuja Alka, Khar Roop and Baboota Sanjula. Floating drug delivery system; A Review. AAPS PharmaSciTech. 2005, 6 (3), E372-E390. • Singh N. Brahma and Kim H. Kwon. Floating drug delivery systems; An approach to oral controlled drug delivery via gastric retention. J. Controlled Release. 2000, 63, 235-25 • Nayak Amit, Maji Ruma and Das Biswarup. Gastro retentive drug delivery system; Review. Asian. J. Pharm. Res. 2010, 3, 2-10.