Osmotic Drug Delivery System

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OSMOTIC DRUG DELIVERY SYSTEM SEMINAR ON PREPARED BY : BHAVIK PATEL PARUL INSTITUTE OF PHARMACY & RESEARCH M.PHARM- PHARMACEUTICS

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Introduction Need For Developing Dosage Form Mechanism Formulation Factor Affecting Drug Release Classification of ODDS Advantages Disadvantages Evaluation Parameters Content

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Introduction Osmotic drug delivery define as the modified-prolong release system, that uses the osmotic pressure for controlled delivery or release of drugs by using osmogens. Osmogens or Osmotic agents are the water soluble substances, that create osmotic pressure in to the system. Drugs can be delivered in a controlled pattern over a long period of time by the controlled or modified release drug delivery systems.

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Simple schematic diagram of Osmotic Drug Delivery Semipermiable membrane Drug material And osmogens O rifice

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Osmosis : The movement of solvent molecules from their lower concentration to higher concentration through semipermiable membrane . Osmotic pressure : Osmotic pressure of a solution is the external pressure that must be applied to the solution in order to prevent it being diluted by the entry of solvent via a process known as Osmosis . These systems can be used for both route of administration i.e. oral and implantation.

Need For Developing Dosage Form :

Need For Developing Dosage Form 1. In order to reduce the dose 2. To decreases dose related side effect 3. To minimizes rate of administration 4. To provide controlled release 5. To increase patient compliance 6. For increase solubility of drugs e.g Atenolol, Glipizide,Verapamil etc.

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Core contain water soluble Osmogens and blended with water soluble or insoluble drug, additives and coating has been carried out which functions as semi permeable membrane. Mechanism Of ODDS

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Since barrier is only permeable to water, initial penetration of water dissolves the critical part of the core, resulting in development of an osmotic pressure difference across the membrane & release of drug from the system.

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Mechanism Of drug release Orifice Semipermiable Membrane Drug & Osmogens

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The drug release is directly proportional to 1.The amount of osmotic agents 2.Drug:Solubility modifier ratio(tartaric acid) 3.Level of pore former The drug release is Inversly proportional to 1.The concentration of polymer coating 2.Membrane weight gain A)Tablet with orifice diameter of 200 – 800 μm showed zero order release and B)The same with 1 mm orifice diameter showed abnormal release

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Dedddddd Delivery Rate Time FIGURE SHOWING THE RATE OF DRUG RELEASE OR RATE OF DELIVERY FROM THE TABLET The drug release is Zero order until all solid material is dissolved Thereafter, the delivery rate decrease parabolically to zero.

Formulation Of Osmotic DDS :

Formulation Of Osmotic DDS DRUGS Drug itself may act as an osmogen and shows good aqueous solubility But if the drug does not possess an osmogenic property , osmogenic salt and other sugars can be incorporated in the formulation. B) SEMIPERMEABLE MEMBRANE Semipermeable membrane must possess certain performance criteria:  It must have sufficient wet strength and water permeability.  It should be selectively permeable to water and biocompatible. polymers such as Ethyl cellulose, agar acetate , poly (glycolic acid) and poly (lactic acid) derivatives are used as semipermeable membrane

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C )Osmotic Agent or osmogen In order to achieve optimized and constant Osmotic Pressure in compartment Osmotic agent must be added to tablet. D)POLYMERS Hydrophilic polymers are hydroxy ethyl cellulose, carboxy methyl cellulose, hydroxyl propyl methyl cellulose, etc . Hydrophobic polymers are ethyl cellulose, wax materials, etc. These polymers are used in the formulation development of osmotic systems for making drug containing matrix core.

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E)SOLUBILIZING AGENTS  Agents that inhibits crystal formation of the drugs or otherwise act by complexation of drug (e.g., PVP, PEG, and Cyclodextrine)  A high HLB surfactant, particularly anionic surfactants (e.g., Tween 20, 60, 80, long chain anionic surfactants such as SLS). F)PLASTICIZERS Permeability of membranes can be increased by adding plasticizer, which increases the water diffusion coefficient. (PEG ) Examples: dialkyl phthalates, trioctyl phosphates, triethyl citrate and other citrates, propionates, glycolates, benzoates, sulphonamides and halogenated phenyls.

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G) WICKING AGENTS It is defined as a material with the ability to draw water into the porous network of a delivery device. The function of the wicking agent to draw water to surfaces inside the core of the tablet, thereby creating channels or a network of increased surface area. . Example: colloidon silicon dioxide, kaolin, titanium dioxide,sodium lauryl sulphate (SLS), low molecular weight polyvinyl pyrrolidone,bentonite etc

Factors Affecting Release Medicament :

Factors Affecting Release Medicament Factors affecting the release rate of medicament from osmotic drug delivery system are , 1. Solubility 2. Osmotic pressure 3. Delivery orifice 4. Membrane type

1.Solubility :

1.Solubility Solubility of drug is one of the most important factors since kinetic of osmotic release is directly related to the drug solubility. The fraction of a drug release with zero order kinetic is given by Where F (z) = fraction release by zero order S = drug solubility in g / cm 3 P = density of core tablet . Drug with solubility less than 0.05 g / cm 3 would release greater than or equals to 95 % by zero order kinetics Drug with solubility > 0.3 g / cm 3 would demonstrate with higher release rate 70 % by zero order.

2. Osmotic Pressure :

2. Osmotic Pressure Rate of drug release from an Osmotic system is directly proportional to Osmotic Pressure of the core formulation In order to achieve optimized and constant Osmotic Pressure in compartment Osmotic agent must be added to tablet Osmotic agents are also used in combination

3.Delivery Orifice :

3 . Delivery Orifice Formation of orifice can take place by,  Laser,  Microdrill,  Modified punches Tablet with orifice diameter of 200 – 800 μm showed zero order release and 2. The same with 1 mm orifice diameter showed abnormal release.

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Laser System Laser drilling is one of the most commonly used techniques to create delivery orifice in the osmotic tablet . Laser beam is fired onto the surface of the tablet that absorbs the energy of the beam and gets heated ultimately causing piercing of the wall and, thus forming orifice. Generally CO 2 laser beam is used for drilling purpose (with output wavelength of 10.6µ). CO2 beam p roduce IR light. The drug delivery orifice was made on the surface of one side of the tablets by using Microdrill. High speed stainless steel drill bits of various diameters (0.4, 0.6, 0.8, 1 mm) were used for drilling. Microdrill

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4.Membrane Type Drug release from osmotic system is largly independent of pH and agitational intensity of GIT. Example are Cellulose Ester, Cellulose Triacetate, Cellulose Propionate, Cellulose Acetate Butyrate, Ester, Ethyl Cellulose and Eudragits. Among above Cellulose Acetate Butyrate is most commanly used since of its, 1. High water permeability, 2. Permeability can be adjusted by varying the degree of acetylation of polymer and also by increasing plastisizer concentration

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Classification of Osmotic drug delivery system 1.Implantable Osmotic Drug Delivery System 2.Oral Osmotic Drug Delivery System

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1. Implantable Osmotic Drug Delivery System the first osmotic pump developed in 1955. Composed of three chambers Water to be loaded prior to use was the drawbacks of rose nelson osmotic pump

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Rose Nelson Pump

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B. Higuchi leeper osmotic pump The Higuchi- Leeper pump is modification of Rose-Nelson pump. It has no water chamber , and the device is activated by water imbibed from the surrounding environment

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C . Higuchi Theeuwes Osmotic Pump This pump comprises a rigid, rate controlling outer semipermeable membrane surrounding a solid layer of salt coated on the inside by an elastic diaphragm. In use, water is osmotically drawn by the salt chamber, forcing drug from the drug chamber .

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When tablet placed in an aqueous environment a saturated solution of drug is developed since Semi permeable membrane draws water inside tablet which generate osmotic pressure. This pressure is relieved by the flow of saturated solution out of device through the delivery orifice. ELEMENTARY OSMOTIC PUMP The table is tablet coated with Semipermiable membrane. Semipermiable membrane Drug material And osmogens O rifice

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CONTROLLED POROSITY OSMOTIC PUMP When Controlled Porosity Osmotic Pump is placed in aqueous environment the water soluble component of coating dissolves and forms micropores in membrane and water diffuses inside the core through microporous membrane, setting up an osmotic gradint and thereby controlling the release of drug.

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Other Osmotic pumps are use for oral are Oral Osmotic Drug Delivery System 1.MODIFIED OSMOTIC PUMP a) Osmotic Pumps for Moderately Soluble Drugs b) Osmotic Pump for Insoluble Drugs 2 .MONOLITHIC OSMOTIC SYSTEM 3 .MULTICHAMBER OSMOTIC PUMP a ) Expandable b) Non Expandable

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ADVANTAGES Zero order release Delivery may be delayed or pulsed High release rate For oral osmotic system, drug release is independent of gastric pH, agitation, presence of food, GI motility The release rate is predictable high degree of IVIVC Production scale up is easy

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DISADVANTAGES Expensive Chance of toxicity due to dose dumping Rapid development of tolerance Hypersensitivity reaction may occur Release of drug depends on : - size of orifice - surface area - thickness and composition of membrane

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EVALUATION OF OSMOTIC TABLET ORIFICE DIAMETER The orifice diameter of the drilled tablets was measured by using R eflecting O ptical M icroscope . The image was transduced to the computer screen using Cannon zoom browser and their size was measured. The porous morphology and orifice diameter of coating membranes ( before and after dissolution studies ) were examined using Scanning Electron Microscope.

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B) COATING THICKNESS Terahertz in-line sensor and Precision Thickness Gauge used to measure Coating Thickness of tablet

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C) FRIABILITY D) THICKNESS E) DISSOLUTION F) WEIGHT VARIATION G) HARDNESS H) IN VITRO EVALUATION

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REFERENCES Pharmaquest Osmotic Drug Delivery System. Aulton M. E., pharmaceutics the science of dosage form design.2 nd Edition 2002 , Churchill livingstone, P=38, 39, 74 , 304, 417. International Journal of Pharmaceutical Research & Technology. Pharmaceutics The Design & Manufacture of Medicines. 3 rd Edition, Michael E. Aulton Page no. 460-461.

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