Oral & dissolution controlled release system

Oral & dissolution controlled release system

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  A SEMINAR ON ORAL CONTROLLED DRUG DELIVERY SYSTEM PRESENTED BY SONAM M. GANDHI
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  INTRODUCTION Oral controlled drug delivery system is a delivery system that provides the continuous oral delivery of drugs at predictable and reproducible kinetics for a determined delivery throughout the course of GI transit.
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  Advantage • Reduce dosage frequency • Reduce fluctuation in circulating drug level • Increase patient compliance • Avoidance of night time dosing • More uniform effect • Reduction in GI irritation and dose related side effects
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  Disadvantage • Highly expansive • Often poor in vivo-in vitro correlation • Dose dumping • poor systemic availability
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  DESIGN AND FABRICATIONOF ORAL STATEM Dissolution controlled release systems Diffusion controlled release system Dissolution & diffusion controlled release system Ion exchange resin drug complex pH dependant formulation Osmotic pressure controlled systems Hydrodynamic pressure controlled systems
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  DISSOLUTION CONTROLLED RELEASE SYSTEM • Sustain release oral products employing dissolution as the rate limiting step are the principle involves in this system. • To achieve this type of approach , the drug particles can be coated with material of varying thickness or by dispersing them in a polymeric matrix.
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  The common formsof dissolution controls formulation are shown below MEMBRANE DRUGS (a) Dissolution controls of drugs release depends on thickness & dissolution rate of the membrane coat (b) Dissolution control of drugs release depends on polymer core erosion
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  • Dissolution controlled drug release system can be divided in to two categories: (1) Encapsulation Dissolution control (2) Matrix Dissolution control (1) Encapsulation Dissolution control: This method involves the coating of particles or granules of drug with slow dissolving materials
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  GRANULES COATED PRODUCT •There are several ways to prepare a drug coated product. • A common method is to coat the seeds with the drug followed by a coat of slow dissolving materials such as carbohydrate sugar and cellulose ,polyethylene glycol, polymeric material, and wax.
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  MICROENCAPSULATION • coacervation / phase separation techniques • Interfacial polymerization • Precipitation • Hot melt • Salting out • solvent evaporation • Electrostatic method.
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  (2) MATRIX DISSOLUTIONCONTROL: • It is also called as monoliths. • The drug is dispersed in media such as bees wax, carnauba wax, caster oil etc which control drug dissolution by controlling the penetration of dissolution fluid in to matrix. • This can be controlled by altering the porosity of the tablet matrix, the presence of hydrophobic additives, and the wettability of the tablet and particle surface.
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  DIFFUSION CONTROLLED RELEASE SYSTEM • There are two type of the diffusion controlled release system : (1) Reservoir devices (2) Matrix devices
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  • (1) Reservoirdevices WATER INSOLUBLE POLYMERIC MEMBRANE DRUG • The drug release mechanism across the membrane involves its partitioning into the membrane and release into the surrounding fluid by diffusion.
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  • The fluxof drug, J , across a membrane in the direction of decreasing concentration is given by Fick's first law; J = - D dc / dx D = Diffusion coefficient in area/ time dc/dx = change of concentration with distance • In term of the amount of drug release , the release rate is given by dM / dt = ADK ΔC / l
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  A = area D = diffusion coefficient K = the partition coefficient of the drug between the membrane and drug core l = diffusion path length ΔC = concentration difference across the membrane
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  • (2) Matrixdevices: Diffusion controls of drugs release by solid drugs dispersed in an insoluble matrix • In this system, a solid drug is dispersed in an insoluble matrix. • The rate of drug release is dependent on THE RATE OF DRUG DIFFUSION but not THE RATE OF SOLID Dissolution.
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  • The drugrelease from this system is given by following equation Q = [ Dε / T ( 2A - εCs ) Cs t ]1/2  Q = weight in grams of drug released per unit surface area  D = diffusion coefficient of drug in the release medium  ε = porosity of matrix  T = tortuosity of the matrix  Cs = solubility of drug in the release medium  A = concentration of drug in the tablet
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  DIFFUSION AND DISSOLUTION CONTROLLED SYSTEM • The main feature of this system is that the drug core is enclosed with a partially soluble membrane. drug Partially Soluble membrane Pores produced by soluble portion of Polymer membrane
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  • The releaseprofile of the drug from this type of the product can be described by following equation : Release rate = AD ( C1 – C2 ) / l A = surface area D = diffusion coefficient of the drug through pores l = Diffusion pathways C1 = concentration of drug in cores C2 = concentration of drug in dissolution medium
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  • The fractionof soluble polymer in the coat will be the dominant factor controlling drug release. • Such a system has been demonstrated to provide a zero order release of Kcl from a tablet and doing the minimize gastrointestinal irritation effect of this compound.
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  Ion exchange resin •This method involves the drug release characteristics depends on the ionic environment of the resin containing drug and should be less effective to the environmental condition such as enzyme content end pH. • Resin[N(CH3)]+X¯ + Z - (Drug-charged resin) Resin [N(CH3)]+Z + X -
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  • The releaserate can be controlled by coating the drug resin complex using the one of the microencapsulating process. Polymer coating Drug containing resin granules
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  • Improvement ofthis ion exchange type drug delivery system is occurs by the development of the pennkinetic system. • In these system, the drug containing resin granules treated with the polymer such as PEG- 400 and further coated with the water soluble polymer such as ethyl cellulose act as a rate limiting barrier to control the drug release. Ethyl cellulose coating Drug containing resin granules Poly ethylene glycol coating
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  pH – INDEPENDENTCONTROLLED RELEASE SYSTEM • This system involves the granules are designed for the oral controlled release of acidic and basic drugs at the rate that is independent of the ph in the GI tract. • They are prepared by mixing a basic or acidic drugs with one or more buffering agents ,granulating with excipients and finally coating with a GI fluid permeable film forming polymer.
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  • When theGI fluid permeates through the membrane , the buffering agents adjust the suitable constant ph, there by constant rate of the drugs release occurs.
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  OSMOTICALLY CONTROLLED RELEASE SYSTEM • In this type of drug delivery system, the osmotic pressure is the driving force that generates constant drug release. Osmotic delivery orifice Semi permeable membrane Osmotic core reservoir containing drug
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  • To regulatethe flow of GI fluid for penetrstion through the semi permeable membrane, a layer of bioerodible polymer can be applied to the external surface of the semi permeable membrane • Several other modification of osmotic pressure controlled drug delivery have been develop. • One system consists of two compartments separated by the movable partition Semi permeable membrane Drug reservoir Movable partition Osmotically active compartment
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  • Another modifiedsystem is one in which delivery orifice is absents .In these system, the GI fluid is penetrate, hydraulic pressure is built up inside until the wall ruptures and the contents are release to the environments. • Osmotic controlled release system requires osmotic pressure to be effective and is independent of its environments.
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  HYDRODYNAMICAL LY BALANCE SYSTEM • This system is design to prolong GI residence time of drug in area of the GIT to minimized drug reaching its absorption site in the solution state. • This type of the tablet or capsules having the less density compared to the GI fluid density. • This type of tablet is prepared by granulating a mixture of drug, excipients, and hydrocolloids such as hydroxyethylcellulose, hydroxypropyle cellulose, and hydroxypropylmethylcellulose.
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  CLASSIFICATION OF HYDRODYNAMICALLY BALANCE SYSTEM (1) Effervescent Floating Dosage Form (2) Non effervescent Floating dosage Form
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  Effervescent Floating DosageForm • These are matrix type of system prepared with swellable polymer such as methylcellulose, chitosan, and various effervescent compounds like sodium bicarbonate, tartaric acid, and citric acid. • These type of tablet comes in contact with the acidic gastric contents, Co2 is liberated and gets entrapped in swollen hydrocolloids, providing buoyancy to the dosage form.
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  Non effervescent Floatingdosage Form • This system is prepared from gel forming or swellable cellulose type of hydrocolloids, polysaccharides, and matrix forming polymer like acrylates. • After the oral administration, this dosage forms sweiis in contact with gastric fluid and attain a bulk density of G.I. • The air entrapped within the swollen matrix imparts buoyancy to dosage form. • The formed swollen gel – like structure acts as a reservoir and allows sustained release of drug through the gelatinous mass.