R. C. Patel Institute of Pharmaceutical Education & Research , Shirpur. Presented By:- * KAMLESH A. WADILE (First Year M. Pharm.) DEPARTMENT OF PHARMACEUTICS A seminar on SOLID DISPERSION 1
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R. C. Patel Institute of PharmaceuticalEducation & Research , Shirpur.
Presented By:-*
KAMLESH A. WADILE(First Year M. Pharm.)
DEPARTMENT OF PHARMACEUTICS
A seminar on
SOLID DISPERSION
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• INTRODUCTION• DEFINITION• MECHANISM• APPLICATIONS• ADVANTAGES• DISADVANTAGES• CLASSIFICATION• METHODS• CONCLUSION• REFERENCES
CONTENT: 2
Introduction:HISTORY :• The conventional methods for reducing particle size include
trituration, ball milling, grinding, etc.• Sekiguchi and Obi first introduced the concept of using solid
dispersion to improve bioavailability of poorly water soluble drugs in 1961.
Solid dispersions are prepared to: 1. To improve drug solubility. 2. To improve drug stability. 3. To mask the bitter taste of drug. 4. To obtain required release profile.
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Definition:• The term solid dispersion is
defined as, a dispersion of one or more active ingredients in an inert carrier or matrix at solid state.
Need:Now a days number of drugs are lipophilic & having a problem of less aqueous solubility, such type of drugs requires enhancement of solubility to enhance its bioavailability.
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MECHANISM:
mechanisms for increasing dissolution rate are: Reduction of particle size. Wettability and dispersibility. Solubilization effect of carrier material on drug.
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APPLICATIONS OF SOLID DISPERSIONS:
• To enhance the absorption of drug and thereby bioavailability.
• To stabilize unstable drug and protects from decomposition.
• To formulate a fast release priming dose in a sustained release dosage form.
• To mask unpleasant taste and odour.
• To enhance solubility of poorly water soluble drug.
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ADVANTAGES OF SOLID DISPERSIONS:
Particles with reduced particle size.
Particles with improved wettability.
Particles with higher porosity of drug.
Drug in amorphous form.
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DISADVANTAGES OF SOLID DISPERSIONS:
Several systems have shown changes in crystallanity and a decrease in dissolution rate on ageing.
Moisture and temperature have more of deteriorating effect on solid dispersions.
Sometimes it is difficult to handle because of tackiness.
During formulation sometimes it may form hard lump which is very difficult to break on large scale.
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CLASSIFICATION OF SOLID DISPERSIONS:A. Simple Eutectic MixtureB. Glass SolutionC. Amorphous Precipitations in crystalline carrierD. Solid Solutions:- According to the extent of miscibility: a) Continuous solid solution b) Discontinuous solid solution According to the molecular size: a) Substitutional type b) Interstitial type
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A) Simple Eutectic Mixture:
These are prepared by rapid solidification of the fused melt of two component that show complete liquid miscibility but negligible solid-solid solubility. Example: Paracetamol-urea
Fig.- Simple binary phase diagram with eutectic eutectic formation TA is melting point of pure A; TB is melting point of pure B; and E is eutectic point.
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B) Glass Solutions: A glass solution is a glassy system in which a solute dissolves in the glassy carrier. The lattice energy, which represents a barrier to rapid dissolution, is much lower in glass solutions than in solid solutions.Example: Citric acid-PVP.C) Amorphous Precipitations in a Crystalline Carrier: This type of solid dispersion is distinguished from simple eutectic mixture by the fact that the drug is precipitated out in an amorphous form.Example: Sulfathiozole-urea.
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D) Solid Solutions: Solid solutions consist of a solid solute dissolved in a solid solvent. These systemsare generally prepared by solvent evaporation or co-precipitation method, wherebyguest solute and carrier are dissolved in a common volatile solvent such as alcohol.
Continuous solid solution:In this system, the two components are miscible or soluble at solid state in allproportions.
Fig.-Hypothetical Phase Diagram of Continuous Solid Solution
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Discontinuous solid solution: In this system, in contrast to the continuous solid solution, there is only a limited solubility of a solute in a solid solvent. Each component is capable of dissolving the other component to a certain degree above the eutectic temperature.
Fig.- Hypothetical Phase Diagram of Discontinuous Solid Solution
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Substitutional type solid solution:As shown in Figure, in this type of solid solution, the solute molecule substitutesfor the solvent molecules in the crystal lattice of the solid solvent. It can form acontinuous or discontinuous solid solution.
Fig.- Substitutional Solid Solution
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Interstitial type solid solution:The solute molecule occupies the interstitial space of the solventlattice. It usually forms only a discontinuous (limited) solid solution.
Fig.- Interstitial Solid Solution
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METHODS OF PREPARATION OF SOLID DISPERSIONS:
1. Melting (fusion) method2. Solvent evaporation method3. Supercritical fluid method4. Hot melt extrusion method5. Melting solvent method
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1. MELTING METHOD:• This method was first reported by Sekiguchi and Obi in 1961.
Physical mixture of drug & carrier
Heated until it is melted
Melt is solidified rapidly in ice bath with stirring
The solid mass crushed & sieved
Ex.- Albendazole and urea solid dispersion 17
2. SOLVENT EVAPORATION METHOD:• This method was first used by Tachibana and Nakamura
Physical mixture of drug & carrier
Dissolve in common organic solvent
Solvent is evaporated until solid film form
Film further dried & sieved
Ex.- solid dispersion sulfa thiazine and urea18
3. SUPERCRITICAL FLUID METHOD:Physical mixture of drug & carrier
Dissolve in supercritical CO2 (as solvent)
Sprayed through nozzle in expansion vessel
Particles immediately formed due to low pressure
Expansion of mixture result in rapid cooling 19
4. HOT MELT EXTRUSION METHOD:Physical mixture of drug & carrier is melted
Processed with extruder
Formation of granules
Sieved
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5. MELTING SOLVENT METHOD:Dissolve drug in liquid solvent
Incorporate above solution in melt of carrier
Evaporated the solvent
Film is left which is dried, crushed, sieved
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CONCLUSION:
Concept of solid dispersion is very easy approach for solubility enhancement when compared with other approaches. So we conclude that solubility of poorly water soluble drugs, stability of unstable drugs and thereby bioavailability can be successfully enhanced by solid dispersion technique based on reported literature.The increase in bioavailability of drug is because of higher solubility enhancement. The higher solubility of solid dispersions is because of conversion of crystalline drug to amorphous form.
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REFERENCES:
1. James Swarbrick and James C. Boylan, Encyclopedia of Pharmaceutical Technology, second edition, volume 1, A-D, pages 1-1032, page no.-641-648.
2. Ladan Akbarpour Nikghalb, Gurinder Singh, Gaurav Singh, and Fazaeli Kahkeshan, Solid Dispersion: Methods and Polymers to increase the solubility of poorly soluble drug, Journal of Apllied Pharmaceutical Science, 2012, volume 2(10), page no.-170-175.
3. D. M. Brahmankar and S. B. Jaiswal, Biopharmaceutics and Pharmacokinetics a treatise, second edition, 2009, Vallabh prakashan, page no.- 351-357.
4. Mahesh Limbachiya, Milan Agrawal, Amit Sapariya and Shailesh Soni, Solubility enhancement techniques for poorly soluble drugs: A review, International Journal of Pharmaceutical Research and Development (IJPRD), 2011, volume 4(04), page no.-74-78.
5. Dhirendra K., Lewis S., Udup N. and Atin K., Solid Dispersions: A review, Pakistan Journal of Pharmaceutical Science, 2009, volume 22(2), page no.-234-246.
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