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GASTRO RETENTIVE DRUG DELIVARY SYSTEM

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GASTRO RETENTIVE DRUG DELIVARY SYSTEM

  1. 1. Department of Pharmaceutics R. C. Patel Institute of Pharmaceutical Education and Research, Prepared by- Mr. Roshankumar G. Bodhe Gastro Retentive drug delivary system
  2. 2. Contents 2 •Introduction •Anatomy and Physiology of Stomach •Need for gastro retention •Suitable and Unsuitable Drugs for GR •Myoeletric Cycle •Approaches for GRDDS •Factors Affecting DDS •Conclusion
  3. 3. Introduction 3 GRDDS:-  Gastroretentive drug delivery is an approach to prolong gastric residence time, thereby targeting site-specific drug release in the upper gastrointestinal tract (GIT) for local or systemic effects.  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. 4 Difference between conventional and GRDDS
  5. 5. 5 NEED FOR GRDDS 5 Oral drug delivery system and Sustained drug delivery systems These drug delivery systems suffer from mainly two adversities: 1. short gastric retention time(GRT) 2. unpredictable short gastric emptying time (GET) which can result in incomplete drug release from the dosage form in the absorption zone (stomach or upper part of small intestine) leading to diminished efficacy of administered dose. To formulate a site-specific orally administered controlled release dosage form, it is desirable to achieve a prolong gastric residence time by the drug delivery. Prolonged gastric retention time (GRT) in the stomach could be advantageous for local action e.g. treatment of peptic ulcer, etc.
  6. 6. 6 SUITABLE DRUGS FOR GRDDS 6 • Drugs acting locally in the stomach. E.g. Antacids and drugs for H. Pylori , Misoprostol. • Drugs that are primarily absorbed in the stomach. E.g. Amoxicillin • Drugs that is poorly soluble at alkaline pH. E.g. Furosamide, Diazepam, Verapamil, etc. • Drugs with a narrow absorption window. E.g. Cyclosporine, , Levodopa, Methotrexate etc. •Drugs which are absorbed rapidly from the GI tract. E.g. Metronidazole, tetracycline. • Drugs that degrade in the colon. E.g. Ranitidine, Metformin. • Drugs that disturb normal colonic microbes E.g. antibiotics against Helicobacter pylori.
  7. 7. 7 UNSUITABLE DRUGS FOR GRDDS 7 1] Drugs That Have Very Limited Acid Solubility E.g. Phenytoin, Etc. 2) Drugs That Suffer Instability In The Gastric Environment. E.g. Erythromycin, Etc. 3) Drugs Intended For Selective Release In The Colon E.g. 5-amino Salicylic Acid And Corticosteroids, Etc.
  8. 8. Anatomy and Physiology of Stomach 8 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. - cecum - appendix -colon -rectum
  9. 9.  GASTRIC EMPTYING  The process of gastric emptying occurs both during fasting and fed state.  In fasted state, the process of gastric emptying is characterized by an interdigestive motility pattern that is commonly called migrating motor complexes (MMC).  This is a series of events that cycle through the stomach every 1.2 to 2 hrs.  In fed state, the gastric emptying rate is slowed down because the onset of MMC is delayed, i.e. the feeding state results in lag time prior to onset of gastric emptying.
  10. 10. 1/26/2018 1010 Phase Duration Phase-I (Basal phase) 30-60 min with infrequent contractions Phase- II (Preburs t phase) 20-40 min with the irregular action potential and contractions as the phase developments, the intensity and the frequency also rises gradually Phase- III (Burst phase) 10-20 min, it contains intense and regular contractions for short periods. It’s due to this wave that all the undigested material is swept from stomach to the small intestine Phase- IV 0-5 min and happens between phase three & one of two successive cycles  Myoeletric Cycle
  11. 11.  FACTORS AFFECTING GRDDS 11 1. Density 2. Size 3. Shape of Dosage form 4. Single or Multiple Unit Formulations 5. Fed or Unfed state 6. Nature of meal 7. Caloric Content 8. Frequency of feed 9. Gender 10.Age 11.Posture 12.Concomitant Drug Administration 13.Biological factor
  12. 12.  Approaches for GRDDS 12
  13. 13. A. Floating System 13 Floating system further classified as :- a) Effervescent system -Gas generating system -volatile liquid containing system b)Non-Effervescent system -Colloidal gel barrier system -Microporous compartment system -floating microspheres -Alginate floatinf beads -Raft forming systems
  14. 14. a) Effervescent system:- 14 Matrix types of system prepared with the help of swellable polymers such as methylcellulose and chitosan and various effervescent agents such as sodium bicarbonate, tartaric acid, and citric acid. Mechanism:-
  15. 15. b) Non-Effervescent system 15 Colloidal gel barrier system (HBS) Preparation Mechanism
  16. 16.  Microporous Compartment System 16 Mechanism: Example: Floating and sustained release granules of diclofenac sodium. Contents: HPC, ethyl cellulose, Ca silicate (floating carrier). Mechanism: Ca silicate is coated with a polymer i.e. HPC. The air is trapped in pores of Ca silicate when coated with polymer. Thus, they float.
  17. 17. Floating microspheres (Micro balloons) 17 Micro balloons or Hallow microspheres loaded with drug prepared by solvent evaporation method. Polymers used polycarbonate, cellulose acetate, calcium alginate, agar, and low methoxylated pectin etc. Buoyancy and drug release depends on quantity of polymers, plasticizer polymer and solvent used. Micro balloons floated continuously over the surface of an acidic dissolution media containing surfactant for >12 hrs.
  18. 18. Alginate floating beads:- 18
  19. 19. 19  Raft Forming System 19 These systems when come in contact with gastric fluids swell and forms cohesive gel. This gel is formed due to sodium alginate solution containing carbonates or bicarbonates. They form raft layer on the top of gastric contents and slowly release drug in the stomach. This system is mainly used in gastro oesophageal reflux treatment with Liquid Gaviscon. They are used for delivery of antacids (Aluminium hydroxide/CaCO3), drugs for GI disorders and infections
  20. 20. 20 B) Low density System 20 This system has less density than the gastric contents and thus remains buoyant in stomach for prolonged period of time. The drug in the formulation is released slowly with a desired rate as formulated. This system increases gastric retention time and reduces the fluctuations in concentration of drug in plasma, thus improving oral bioavailability. Drugs which are absorbed mainly through upper part of stomach are most suitable candidates
  21. 21. 21  High Density System 21 High density systems are retained in antrum/rugae of stomach and are having density more than the threshold density (3 gm/cm3). For manufacturing of these systems various diluents like barium sulphate, titanium dioxide, iron powder, zinc oxide etc. are used for coating. • Disadvantages: Technically manufacturing of this system is difficult as it is difficult to achieve such a high density.
  22. 22. 22 C. Swelling and Expanding System 22  These are the systems, which on reaching to the gastric environment swells and becomes larger in size. Generally, when the gastric emptying occurs, all the contents in gastric cavity are transferred to the intestine through pyloric sphincter. In the phase III of MMC, when housekeeper waves are present, pyloric sphincter enlarges to 13-18 mm in size.  For dosage system to remain in gastric cavity should swell more than size of pyloric sphincter to retain in gastric environment for longer period of time, even in fed state.
  23. 23. Cont… For the sustained and controlled release of drug, swelling polymer is used which retards the drug release. Swelling polymer when comes in contact with gastric contents, imbibes water and swells due to the presence of chemical/physical cross-links in the hydrophilic polymer network.  This cross-link prevents the dissolution of polymer by maintaining physical integrity of dosage form.
  24. 24. 5. Bio/ Muco-adhesive System 24 These system bind to gastric epithelial cell surface or mucin of the stomach. This will enhance the retention time of the drug formulation in the stomach. The natural or synthetic polymers are used in the formulations which interact with mucin to form bio/muco-adhesive bonds. Polymers showing adhesive mechanism with biological membrane are called bioadhesive polymers and those showing adhesive mechanism with mucus lining of GI mucosal surface are called mucoadhesive polymers. Examples of Bioadhesive Polymers PAA, chitosan, sodium alginate, HPMC, sucralfate, tragacanth, dextrin, PEG. Natural hydrophilic polymers can also be used alone or in their appropriate combinations in formulation of matrix tablets. E.g.: locust bean gum, guar gum, karaya gum, xanthun gum etc.
  25. 25. Properties of ideal mucoadhesive polymers Non-toxic, non-absorbable from GI tract. It should have molecular flexibility, specific molecular weight, hydrophilic functional groups, conformation and chain length. It should form non-covalent bond with mucin-epithelial surface. It should have quick adherence to moist surfaces. It should easily incorporate drug. It should offer no hindrance to drug release. It should have specific site of attachment. It should be easily available and economical.
  26. 26. Super porous Hydro gel System 26 These system show mechanism of capillary wetting through the number of pores they have. The average pore size is more than 100 micrometer. The system swells to very large size and have swelling ratio 100 or more within a minute after coming in contact with gastric fluid. The system can withstand pressure exerted by gastric contraction as having sufficient mechanical strength
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  29. 29.  Novel Approaches in Gastro-retentive Drug Delivery System 29 1. Ion Exchange Resins 2. Tablets with Hollow Cylinder 3. Unfolding System 4. Multilayer Flexible Film 5. Floating In-Situ Gel 6. Dual Working System 7. Floating Pulsatile System
  30. 30. CONCLUSION 30 • Gastro retentive drug delivery systems have emerged as a current approach of controlled delivery of drugs that exhibit an absorption window. • All these drug delivery systems have their own advantages and drawbacks. • To design a successful GRDDS, it is necessary to take into consideration the physicochemical properties of the drug, physiological events in the GIT, formulation strategies, and correct combination of drug and excipients.

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