SOLID DISPERSIONS

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SOLID DISPERSIONS : 

SOLID DISPERSIONS IMPROVING DRUG SOLUBILITY USING SOLID DISPERSIONS. Presented By M.PRAVEEN REDDY Under the guidance of C SHEKAR REDDY.KAMIREDDY

Slide 2: 

DEFINITION: Solubility is defined as the ability of a substance to form a solution with another solution

It helps for the identification of potential screening and bioavailability issues .It is important for the conformation of bioavailability issues. During early trials of drugs it is used in the design of veterinary and human formulations.Solubility knowledge is needed for biopharmaceutical classification, biowaivers, bio equivalence.it is also required for formulation, optimization and salt selection.Solubilty also effects the optimization of manufacturing process. : 

It helps for the identification of potential screening and bioavailability issues .It is important for the conformation of bioavailability issues. During early trials of drugs it is used in the design of veterinary and human formulations.Solubility knowledge is needed for biopharmaceutical classification, biowaivers, bio equivalence.it is also required for formulation, optimization and salt selection.Solubilty also effects the optimization of manufacturing process. IMPORTANCE OF SOLUBILITY:

Slide 4: 

SOLID DISPERSIONS Chio and Regelman defined the term solid dispersion as “dispersion of one or more ingredients in an inert carrier or an matrix of solid state prepared by various methods”. Melting Fusion method Solvent Method Melt solvent Method Melt extrusion Method Lyophilization technique Use of surfactants Electrospinning

Slide 5: 

List of Poorly Soluble Drugs with Hydrophilic Carriers:

BIO PHARMACEUTICS SYSTEM OF CLASSIFICATION : 

BIO PHARMACEUTICS SYSTEM OF CLASSIFICATION

The drugs are classified in BCS on the basis of following parameters: : 

The drugs are classified in BCS on the basis of following parameters: 1.Solubility2. Permeability3. Dissolution The class boundaries for these parameters are: Solubility class boundaries- Permeability class boundaries- Dissolution class boundaries-

Types of solid Dispersions: : 

Types of solid Dispersions: Eutetics-the first type of solid dispersions prepared Amorphous precipitations in crystalline matrix – rarely encountered Solid solutions – 1.continuous - Miscible at all composition 2.Discontinuous -Partially miscible, 2 phases even Substitutional solid solutions-Molecular diameter of drug (solute) differs less than 15% from the matrix (solvent) diameter. Interstitial solid solutions-Drug (solute) molecular diameter less than 59% of matrix (solvent) diameter.

Slide 9: 

Glass suspension- particle size of dispersed phase dependent on cooling/evaporation rate many solid dispersions are of this type. Glass solution - Requires miscibility OR solid solubility, complex formation or upon fast cooling OR evaporation during preparation, many (recent) examples especially with PVP

Melting fusion method : 

Melting fusion method Proposed by Sekiguchi and Obi Involves the preparation of physical mixture of a drug and a water-soluble carrier and heating it directly until it melted. The melted mixture is then solidified rapidly in an ice-bath under vigorous stirring. The final mass is crushed, pulverized and sieved. Appropriately this has undergone many modifications in pouring the homogenous melt in the form of a thin layer onto a ferrite plate or a stainless steel plate cooled by flowing air or water.

Solvent method: : 

Solvent method: The physical mixture of the drug and carrier is dissolved in a common solvent, which is evaporated until a clear, solvent free film is left. The film is further dried to constant weight. The main advantage of the solvent method is thermal decomposition of drugs or carriers can be prevented because of the relatively low temperatures required for the evaporation of organic solvents.

Melting solvent method (melt evaporation): : 

Melting solvent method (melt evaporation): It involves preparation of solid dispersions by dissolving the drug in a suitable liquid solvent and then incorporating the solution directly into the melt of polyethylene glycol. which is then evaporated until a clear, solvent free film is left. The film is further dried to constant weight. The 5 –10% (w/w) of liquid compounds can be incorporated into polyethylene glycol6000 without significant loss of its solid property.

Lyophilisation Technique: : 

Lyophilisation Technique: Freeze-drying involves transfer of heat and mass to and from the product under preparation. Lyophilisation has been thought of a molecular mixing technique where the drug and carrier are co dissolved in a common solvent, frozen and sublimed to obtain a lyophilized molecular dispersion.

The use of surfactant: : 

The use of surfactant: Adsorption of surfactant on solid surface can modify their hydrophobisity , surface charge, and other key properties that govern interfacial processes such as flocculation/dispersion, floatation, wetting, solubilization, detergency, enhanced oil recovery and corrosion inhibition. Solvation/plasticization, manifesting in reduction of melting the API. Because of these unique properties, surfactants have attracted the attention of investigators for preparation of solid dispersions

Electrospinning: : 

Electrospinning: Electrospinning is a process in which solid fibers are produced from a polymeric fluid stream solution or melt delivered through a millimeter-scale nozzle. This process involves the application of a strong electrostatic field over a conductive capillary attaching to a reservoir containing a polymer solution or melt and a conductive collection screen.

Slide 16: 

Approaches to improve the solubility:

Marketed formulation of solid dispersion : 

Marketed formulation of solid dispersion

Advantages: : 

Advantages: - Processing equipment available at small and large scale. - Thermolabile products. - Relatively high drug doses are possible. - Most carriers can act as “solid” solvent. Carriers (mainly surface active agents) can maintain super saturation in GI tract. - Down stream processing is possible.

Drawbacks: : 

Drawbacks: Laborious and expensive methods of preparation. Reproducibility of physicochemical characteristics. Difficulty in incorporating into formulation of dosage forms. Scale-up of manufacturing process, and Stability of the drug and vehicle. Increasing number of drugs with low solubility in organic solvents.

References: : 

References: Gibaldi M. Ed., In; Biopharmaceutics and clinical pharmacokinetics, 4th Edn, Pharma Book Syndicate, Hyderabad, 2005, 48 Ansel H C, Allen L V and Popovich CG. Eds. In; Pharmaceutical dosage forms and drug delivery systems, 7th Edn, Lippincott Williams and Wilkins, 2000, 60-61,66. http://www.pharmainfo.net/reviews/biopharmaceutical-classification-drugs http://en.wikipedia.org/wiki/Biopharmaceutics_Classification_System