NDDS introduction

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3 Why do we need controlled drug delivery? Reasons Medical - Optimum dose, at the right time, and in the right location Industrial - Efficient use of expensive ingredients, reduction in production costs Societal - Beneficial to patients, better therapy, improved comfort and standard of living

3 Basic modes of drug delivery system:: 

3 Basic modes of drug delivery system: Targeted Drug Delivery Controlled Drug Delivery Modulated Drug Delivery 4

3 Types of Drug Delivery Rates: 

3 Types of Drug Delivery Rates Zero order release rate: k = constant M = mass of active agent released t = time 5 dM t / dt = k

2) First Order Release Rate:: 

2) First Order Release Rate: After integration, 6 dM t / dt = k(M 0 - M t ) dM t / dt = KM 0 e -kt

3) Square root of time release:: 

3) Square root of time release: 7 dM t / dt = K/ t 1/2

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Factors affect the design of controlled release product: 

Factors affect the design of controlled release product Physicochemical Properties of drug Route of Administration Acute/ chronic therapy Target sites The patient The disease state 9

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10 Controlled Release System Dissolution controlled Diffusion & dissolution controlled Water penetration controlled Chemically controlled Hydrogels Ion-exchange resin Diffusion controlled matrix Reservoir Reservoir & monolithic Encapsulation Matrix cation anion Environment responsive Chemically controlled Swelling controlled Diffusion controlled Erodible system Drug covalently linked with polymer Osmotically controlled Swelling controlled

Classification of controlled release system: 

Classification of controlled release system Type of system Rate control mechanism Diffusion controlled Diffusion through membrane Water penetration controlled Osmotic transport of water through semi permeable membrane Chemically controlled Surface erosion or bulk erosion Regulated system External application of magnetic field or ultrasound 11

1) Matrix Diffusion Types : 

1) Matrix Diffusion Types Rigid Matrix Diffusion Materials used are insoluble plastics such as PVP & fatty acids. Swellable Matrix Diffusion Also called as Glassy hydrogels . Popular for sustaining the release of highly water soluble drugs. Materials used are hydrophilic gums. Examples : Natural: Guar gum, Tragacanth . Semi-synthetic: HPMC, CMC, Xanthum gum. Synthetic : Polyacrilamides . 12

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13 Matrix system Rate controlling step: Diffusion of dissolved drug in matrix.

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14 Drug and excipients are mixed with polymers such as Hydroxypropyl methylcellulose (HPMC) and Hydroxypropyl cellulose (HPC). Tableted by conventional compression. Release from the tablet takes place by combination of : water diffuses into the tablet, swells the polymer and dissolves the drug. drug may diffuse out to be absorbed.

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16 MATHEMATICAL EXPRESSION OF MATRIX TYPE OF DRUG DELIVERY SYSTEMS Q = (A- Cp/2) δp Where A as initial amount of drug solid impregnated in a unit volume of polymer matrix. Cp = solubility of drug in polymer phase K = partition coeffient Ds = diffusivity of drug in solution Dp = diffusivity of drug in polymer t = time dt = differential length of time δd = thickness of diffusion layer δp = thickness of outer membrane δp 2 +

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17 At very early stage of the drug release process, the depletion zone dp is small that, δp << The constant drug release rate, = =

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18 Now, If the magnitude of dp is substantially large after the lapse of time or magnitude of partition coefficient is very large and or the thickness of diffusion layer δd is small, δp 2 >> so the drug release rate can be written as, = [(2A-Cp) CpDpt ] 1/2

Reservoir System: 

Reservoir System Also called as Laminated matrix device. Hollow system containing an inner core surrounded in water insoluble membrane. Polymer can be applied by coating or micro encapsulation. Rate controlling mechanism - partitioning into membrane with subsequent release into surrounding fluid by diffusion. Commonly used polymers - HPC, ethyl cellulose & polyvinyl acetate. 19

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20 Reservoir System Rate controlling steps : Polymeric content in coating, thickness of coating, hardness of microcapsule.



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22 22 MATHEMATICAL EXPRESSION OF RESERVOIR TYPE OF DRUG DELIVERY SYSTEMS The cumulative amount of drug Q released from unit surface area of reservoir type delivery device is expressed by mathematical expression. This equation suggest that the drug molecules release under the diffusion layer limiting partition controlled process & the drug release rate is linearly proportional to product of solution concentration & solution diffusivity Ds & is inversely proportional to the thickness of hydrodynamic diffusion layer dd.

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23 2) Dissolution Matrix Type Also called as Monolith dissolution controlled system since the drug is homogenously dispersed throughout a rate controlling medium waxes (beeswax, carnuba wax, hydrogenated caster oil etc) which control drug dissolution by controlling the rate of dissolution; 1. Altering porosity of tablet. 2. Decreasing its wettebility . 3. Dissolving at slower rate. Exhibit First order drug release. Drug release determined by dissolution rate of polymer.

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24 Soluble drug Slowly dissolving matrix

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25 Encapsulation Called as Coating dissolution controlled system since the drug encapsulated, with slowly dissolving material like cellulose, PEG, PMA ( polymethylacrylates ) & waxes. Dissolution rate of coat depends upon stability & thickness of coating. Soluble drug Slowly dissolving or erodible coat

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26 3) Dissolution & Diffusion Controlled Release system Drug encased in a partially soluble membrane. Pores are created due to dissolution of parts of membrane. It permits entry of aqueous medium into core & drug dissolution. Diffusion of dissolved drug out of system. Ethyl cellulose & PVP mixture dissolves in water & create pores of insoluble ethyl cellulose membrane. Insoluble membrane Pore created by dissolution of soluble fraction of membrane Entry of dissolution fluid Drug diffusion

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27 4) Osmotic Pressure Controlled System Drug may be osmotically active, or combined with an osmotically active salt (e.g., NaCl ). Semi-permeable membrane usually made from Cellulose acetate. Drug is pumped out continuously because of osmotic pressure gradient. More suitable for hydrophilic drug. Provides zero order release

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28 Osmotic Pressure Controlled System

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29 5) Chemically Controlled Released Systems Systems that change their chemical structure, when exposed to biological fluids. Mostly, biodegradable polymers, are designed to degrade as a result of hydrolysis of the polymer chains into biologically safe and progressively smaller moieties and thus releasing API. It is of two types; Erodible Systems Pendent Chain System

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30 Chemically controlled released Systems Erodible Systems Two types; Bulk Erosion : Polymer degradation may occur through bulk hydrolysis. Surface Erosion : Degradation occur at the surface of the polymers e.g. Polyorthoesters & Polyanhydrides , resulting a release rate is proportional to the surface area of the delivery system.

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31 Chemically controlled released Systems Drug delivery from (a) bulk-eroding (b) surface-eroding biodegradable systems

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32 Chemically Controlled Released Systems Pendent Chain System Consist of linear homo or copolymers with drug attached to its backbone chains. e.g. Hydroxy propyl methyacrylamide etc. Release drug by hydrolysis or enzymatic degradation of the linkages Follows zero order kinetics, cleavage of the drug is rate determining step.

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33 6) Hydrogels Three dimensional structures composed of primarily hydrophilic polymers having chemical or physical cross links which provides a network structure to hydrogels . Insoluble because of network structure and provides desirable protection of liable drugs, peptides and proteins

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34 Hydrogels Drug delivery from matrix swelling-controlled release systems

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35 7) Ion-Exchange Resins Controlled Release Systems Such system provide control release of an ionic (ionisable) drug. Ionisable drug is absorbed on ion-exchange resins granules and then granules are coated with water permeable polymers using spray drying technique. H + Cl - in the gastric fluid are exchange with cationic and anionic drugs from the ion-exchange resins.

Biodegradable polymers: 

Biodegradable polymers Polymers: macromolecule consisting of large number of monomers. Definition: Polymers degraded by biological means such as enzymes, micro-organisms. The biodegradable polymers can be defined as polymers comprised of monomers linked to one another through functional groups and have a unstable linkage on backbone. They are biologically degraded or eroded by enzymes introduced in vitro or generated by surrounding living cell or by non- enzymetic process into oligomers or monomers that can be metabolized or excreated . 36

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37 Biodegradable matrices were involved , the drug release would be total from the matrix degradation – controlled device, unless a strong interaction between the drug and degrading matrix. so, it produce more steady release.


Characteristics Predictability of biodegradation kinetics Ease of fabrication / processability Their toxicity / antigenicity / anti-inflammatory profile following erosion Absence of toxic endogenous impurities or residual chemicals used in their preparation, e.g. cross-linking agents Achieve controlled heterogenous erosion without any additive Acceptable shelf-life Ability to withstand sterilization procedures Degradation products that are excreted readily Regulatory approval 38

Classification according to the mechanism of polymarization:: 

Classification according to the mechanism of polymarization : There are two types of polymerization methods reported Chain polymerization :- These polymerizations are also known as Vinyl polymerization because most of the monomers of interest are compounds that contains a vinyl group . In general chain polymerization is done by following four types according to the nature of active center Free radical , Anionic chain polymerization , Cationic polymerization and Ziegler- Natta polymerization . 39

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40 40 B . Step growth polymerization :- It is any two species in the reaction mixture can react by specific reaction between two appropriate functional groups A polymerization mechanism in which each reaction between monomers is a discrete and independent step .

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41 A) NATURAL POLYMERS A) Proteins B) Polysaccharides 1. Albumin 1. Starch 2. collagen 2. Hyaluronic acid 3. Gelatin 3. Dextran 4. Alginic acid 5. Xanthan Gum 6. Guar Gum 7. Rosin 8. Inulin 9. Pectin 10. Amylose 11. Cyclodextrin

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42 B) Synthetic polymers Polyesters: eg . PLA, PGA, Poly hydroxy butyrate (PHB),Poly-e- caprolactone (PCL), Polymalic acid,Polydioxanone (PDA) Polyunhydrides : eg . Poly sebacic acid (PSBA), poly adipic acid (PAPA), Poly terphthalic acid (PTA) Polyamides: eg . Poly imino carbonate (PIC), Poly amino acid (PAA)

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43 4. Phosphorus Based : eg . Polyphosphates, Polyphosphazene , 5. Others : eg . Polycyanoacrylates (PCA), Polyurathanes , Polyorthoesters , Polyacetals .

Polymer Degradation and Erosion: 

Polymer Degradation and Erosion Degradation is the process of chain cleavage leading to a reduction in molecular weight. It is occur in 2 phase. 44

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45 PHYSICAL EROSION MECHANISM (A) Bulk-eroding system ( PLA,PGA) ) Degradation takes place throughout the whole of the polymer matrix. Loss of physical integrity. Ingress of water is faster than the rate of degradation (B) Surface-eroding system ( poly( ortho )esters and polyanhydrides ) Eroded from the surface Physical integrity maintained Mass loss is faster than the ingress of water into the bulk

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46 Polymer Degradation by Erosion

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47 polymer Advantages Disadvantages collagen Easy to isolate & purify in large quantities Biocompatible & non-toxic profile well established physiological, structural & immunological properties Amenable to easy processing to various forms In vivo swelling & resultant poor dimensional stability Variability in drug release kinetics Low mechanical strength & elasticity in vivo Residual aldehyde cross linking agents cause tissue irritation Chances of triggering an antigenic response Albumin Primary advantage is its bio degradation in to natural products Easy avaibility Absence of toxicity antigenisity interaction between the drug & albumin matrix nature & degree of cross linking present of enzymes & PH of the environment gelatin easy availability low antigen profile poor binding to drug molecules & low temperature preparation technique that reduces the chances of drug degradation ---------------------------------------- Alginates it can be easily fabricated in to particulate carriers they can be easily prepared in aqueous solution at room temperature they protects antigens/vaccines against degradation in the gastrointestinal tract they bypass the stomach ------------------------------------------------------

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48 Some Individual applications of Biodegradable polymers Polymers Their applications Collagen In Wound repairing Chitosan gelling agent Dextran Plasma volume expander Lectins as mucoadhesive Cyclodextrins,guar-gum,pectin,dextran,inulin Delivery of drug to colon Poly–e- caprolactone Microsphere,implants

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49 PLA,PLGA Exepient for injectible drugs PLA+Doxicyclin hyclate –periodontal disease PLGA+Growth hormone---growth deficiency PLA+Bone morphogenic protein----in Bone tissue engineering PLA+Leuprolide Acetate ----in prostate cancer Rosin As a adhesive in TDDS Polyurathanes Synthetic skin ( synthaderm ) Lyofoam In chromatography as Dextran Gel

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50 Smart polymer Also called ‘ Stimulus Responsive’ Similar to biopolymer Smart polymer Undergo reversible changes Hydrophilic state Hydrophobic state Precipitation Change in size Alteration in content Driving force for this, pH Temperature Adding Opposite charge polymer

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51 POLYMER THERAPEUTICS It provides for an innovative opportunity to design novel pharmaceuticals that have real potential to improve efficacy in life threatening disease such as cancer. It offers the opportunity for cell or organ specific targeting.

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52 52 Application of SMART POLYMER Immobilized catalyst Drug delivery Chemical valve Thermo-Responsive surfaces Biometic actuators Bio- Seperation Thermo-Responsive chromatography Cell detachment Thermally controlled biocatalyst Immobilized viable cells Reversible soluble biocatalyst Aqueous two-phase polymer systems Affinity precipitation


References www.biodeg.net/Biodegradable polymers www.bioen.utah.edu/faculty/pat/.../ Biodegradable %20Materials.ppt “Controlled Drug Delivery- Concepts and advances” by S.P.Vyas and Roop K.Khar , vallabh prakashan, page no: 1 to 54, 97 to 155. 53