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Microparticles are defined as particulate dispersions or solid particles with a size in the range of 1-1000 μm


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1 Microparticles PRESENTED BY alok kr vishwakarma (alokkumar_89@yahoo.com) katiyar bipin sarvesh ( bipinkatiyar87@gmail.com ) Dept of pharmaceutics psit,kanpur M.PHARM(PHARMACEUTICS)


2 INTRODUCTION Microparticles are defined as particulate dispersions or solid particles with a size in the range of 1-1000 μm. The drug is dissolved,entrapped, encapsulated or attached to a microparticle matrix. Depending upon the method of preparation, microparticles,microspheres or microcapsules can be obtained.

Different categories of microparticles:

3 Different categories of microparticles

The advantages of using microparticulate drug delivery system:

4 The advantages of using microparticulate drug delivery system 1. Particle size and surface characteristics of microparticles can be easily manipulated to achieve both passive and active drug targeting after parenteral administration

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5 2. They control and sustain the release of the drug during the transportation and at the Site of localization, altering organ distribution of the drug and subsequent clearance of the drug so as to achieve increase in drug therapeutic efficacy and reduction in side effects

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6 3.Controlled release and particledegradation characteristics can be readily modulated by the choice of matrix constituents. Drug loading is relatively high and drugs can be incorporated into the systems without any chemical reaction; this is an important factor for preserving the drug activity.

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7 4. Site-specific targeting can be achieved by attaching targeting ligands to surface of particles . 5. The system can be used for various routes of administration including oral, nasal, parenteral, intra-ocular etc.

Fabrication of microparticles:

8 Fabrication of microparticles Points to be considered for fabrication are: I. The stability and biological activity of the drug must not be affected by the processing parameters employed in the fabrication of drug-loaded microparticles. II. The yield of microparticles should have the desired size range and the drug encapsulation efficiency should be high. III. The particle quality and the drug release profile should be reproducible.

1) Solvent evaporation and extraction based processes:

9 1) Solvent evaporation and extraction based processes Single emulsion process: The process involves oil-in-water (o/w) emulsification. The o/w emulsion system consists of an organic phase comprised of a volatile solvent with dissolved polymer and the drug to be encapsulated , emulsified in an aqueous phase containing a dissolved surfactant.

Schematic of w/o/w in-liquid drying process for microparticle preparation:

10 Schematic of w/o/w in-liquid drying process for microparticle preparation

Encapsulation using oil-in-water emulsion technique:

11 Encapsulation using oil-in-water emulsion technique

ii) Double emulsion process::

12 ii) Double emulsion process: A double emulsion process is usually employed for drugs not soluble in an organic solvent. A solid-in-oil-in-water emulsion (s/o/w) process could be used to encapsulate a drug provided its form is of small size. The size of the drug crystal should be at least an order of magnitude smaller than the desired microparticle diameter in order to avoid large bursts associated with dissolution of larger crystals. Smaller crystals will be homogeneously distributed throughout the organic droplets created in emulsion. Hydrophilic drugs (cisplatin, doxorubicin) have been encapsulated using this method.

2) Phase separation::

13 2) Phase separation: The process consists of decreasing the solubility of the encapsulating polymer by addition of a third component to the polymer solution . The process yields two liquid phases: the polymer containing coacervate phase and the supernatant phase depleted in polymer. The drug which is dispersed /dissolved in the polymer solution is coated by the coacervate. Thus the coacervation process consists of the following three steps: i) phase separation of the coating polymer solution, ii) adsorption of the coacervate around the drug particles, and iii) solidification of the microspheres.

3) Spray drying::

14 3) Spray drying: Spray-drying is a widely used method in the pharmaceutical industry and has been investigated by several researchers as a method for formulating biodegradable microparticles. It is rapid, convenient, easy to scale-up, involves mild conditions, and is less dependent on the solubility parameters of the drug and the polymer. The method typically uses drug dissolved or suspended in a polymer solution (either organic or aqueous solvent depending on the polymer used).

Microparticle preparation -Formulation considerations:

15 Microparticle preparation -Formulation considerations Stabilizer Stabilizer plays an important role in the formulation of microparticles. In the absence of an appropriate stabilizer, the high surface energy of micro-sized particles can induce agglomeration or aggregation of the drug crystals.

2. Organic solvents:

16 2. Organic solvents Organic solvents may be required in the formulation of microparticles if they are to be prepared using an emulsion or microemulsion as a template.

4. Other additives:

17 4. Other additives Microparticles may contain additives such as buffers, salts and cryoprotectant, depending on either the route of administration or the properties of the drug moiety.

Characterization of microparticles:

18 Characterization of microparticles The essential characterization parameters for microparticles are as follows. 1) Mean particle size and particle size distribution: The mean particle size and the width of particle size distribution are important characterization parameters as they govern the dissolution velocity, physical stability and even biological performance of microparticles

2) Crystalline state and particle morphology:

19 2) Crystalline state and particle morphology The assessment of the crystalline state and particle morphology together helps in understanding the polymorphic or morphological changes that a drug might undergo when subjected to microsizing.

3)Dissolution velocity:

20 3)Dissolution velocity The determination of dissolution velocity is very important as this parameter help to anticipate any change in the in-vivo performance (plasma peaks and bioavailability) of the drug.

4) In-vivo biological performance::

21 4) In-vivo biological performance : The establishment of an in-vitro/in-vivo correlation and the monitoring of then in-vivo performance of the drug is an essential part of the study,irrespective of the route and the delivery system employed.

Applications of microparticles in drug delivery:

22 Applications of microparticles in drug delivery Oral drug delivery Orally administered antibiotics such as atovaquone and bupravaquone reflect the problem of low oral bioavailability. Microsizing of such drugs can lead to a dramatic increase in their oral amelioration in oral bioavailability can beattributed to the adhesiveness of the drug absorption and subsequently bioavailability. The microparticles, increased surface area (due to reduction in particle size by 10–50-fold), and increased saturation solubility, leading to an increased concentration gradient between the gastrointestinal tract lumen and blood, and increased dissolution velocity. The subsequent reduction in drug dose, rendering the therapy cost-effective and obliterating any undue drug dumping in the body.

2) Ocular drug delivery:

23 2) Ocular drug delivery Microsuspensions, by their inherent ability to improve the saturation solubility of the drug, represent an ideal approach for ocular delivery of hydrophobic drugs. Moreover, the microparticulate nature of the drug allows its prolonged residence in the cul-de-sac, giving sustained release of the drug.



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