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Hejal parekh presentation

  4. 4. INTRODUCTION A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. The study of the crystalline form as a part of preformulation study is termed as crystallinity study. 4
  5. 5. CLASSIFICATION OF CHEMICAL COMPOUND Solids Amorphous Crystalline (Non-crystalline) Single entity Molecular adducts Non-stoichiometric Stoichiometric Polymorphs Inclusion compounds compounds CageEnantiotropic Monotropic Channel Layer Hydrates Solvates (Clathrate) 5
  6. 6. AMORPHOUS COMPOUND They have atoms or molecules randomly placed as in a liquid. They are typically prepared by: Lyophilization E.g. Fluprednisolone in tert-butanol. Rapid quenching of chloramphenicol palmitate solution in hydrophilic solvent. Rapid quenching of melted chloramphenicol palmitate in the refrigerator to -10˚ Precipitation is also used to prepare the amorphous prompt insulin zinc suspension. 6
  7. 7. EFFECT ON INSULINNO TYPE OF INSULIN FORM OF ONSET DURATION OF. INSULIN OF ACTION ACTION1 Prompt insulin- Amorphous Fast Short zinc suspension (semilente)2 Extended crystalline Slow Long insulin-zinc suspension (ultralente)3 Insulin-zinc 30% Fast Intermediate suspension amorphous+ (lente) 70% crystalline 7
  8. 8. Amorphous forms are of :- Higher thermodynamic energy Greater solubility and dissolution rate. But due to high energy they are unstable and revert back to a stable form.E.g. Amorphous novibiocin suspension.Agents like methylcellulose, polyvinylpyrollidone, and several alginic acid derivatives such as sodium alginate and propylene glycol alginate are used to prevent such condition. 8
  9. 9. POLYMORPHS Many drug substances can exist in more than one crystalline form with different space-lattice arrangements. This phenomenon is known as polymorphism and the different crystalline forms as polymorphs. Drugs like barbiturates have polymorphic forms. Also steroid hormones have 42 and sulphonamides have 30 polymorphic forms. 9
  10. 10. SOLVATES (PSEUDOPOLYMORPHISM)Solvates are molecular complexes that have incorporated thecrystallizing solvent molecule in their specific lattice positionand in fixed stoichiometry.Estradiol forms highest number of solvates with all 30solvents.Other examples areerythromycin, chloramphenicol, ampicillin, sulphanilamideetc. Solvates can be distinguished from polymorphs by observingbubbles of gas in silicon oil upon heating. 10
  11. 11. CLATHRATESA clathrate is a single-phased solid with two distinctcomponents: the host and the guest.The guest is retained in the closed cavities provided by thecrystalline structure of the host.Thus it is a non-stoichiometric molecular adduct.The major classes of clathrates are hydroquinoneclathrates, water clathrates, phenol clathrates etc. 11
  13. 13. COMPARISON OF THE MECHANICAL PROPERTIES OF THE COMPACTS OF THE CRYSTALLINE AND AMORPHOUS FORMS OF A DRUG SUBSTANCE CRYSTALLINE FORM AMORPHOUS FORM More ductile (low Least ductile (high indentation hardness indentation hardness value) value) Form compacts with Form compacts with lowest highest tensile tensile strength strength Compacts have low Compacts have high brittleness value brittleness value Require higher Require lower compression compression stress stress 13
  14. 14. COMPARISON OF SOLUBILITY OF CRYSTAL, SOLVATE AND HYDRATE:Amorphous form more soluble than a correspondingcrystalline form.The dissolution rates of hydrates are less than correspondinganhydrous crystalline form. E.g.gluthethimide, theophylline, caffeine, succinylsulphathiazole, phenobarbitol.The dissolution rates for organic solvates are higher thancorresponding pure crystalline form. E.g. 1,4-dioxane solvateof nifedipine shows better solubility than dehydrate form. So organic solvates should be preferred in place of purecrystals which solves both problems, solubility andstability, but only if ICH guidelines about limits of organicresidues permit. 14
  15. 15. Crystals are of two types:-Irregularly shaped crystals known as anhedral orallotriomorphic.Definite shaped crystals bound by plane faces known aseuhedral or idiomorphic. Any crystal is characterized by its internal structure andhabit. Habit is the description of the outer appearance of acrystal whereas the internal structure is the moleculararrangement within the solid. 15
  16. 16. CRYSTAL SYSTEM (INTERNAL STRUCTURE)The most symmetric system is cubic system.Other six systems, in order of decreasing symmetry, arehexagonal, tetragonal, rhombohedral (also known astrigonal), orthorhombic, monoclinic and triclinic.Thus there are fourteen types of unit cell called as theBravais lattices.We can identify the various planes of crystal using thesystem of Miller indices. 16
  18. 18. CRYSTAL HABITThere are five types of crystal habit widely recognized:Platy: platesTabular: moderate expansion of two parallel facesPrismatic: columnsAcicular: needle-likeBladed: flat acicularThese occur in all the seven systems. 18
  19. 19. Crystal habit:can be quantitatively expressed in terms of Aspect ratio (AR).AR defined as the ratio of length to width and values of ARapproaching 1 (spherical or cube shape) are considered to bepharmaceutically good.It is preferable to keep the AR values below 5 so as to avoidproblems with flow.AR in polar solvents was as high as 9.4 in comparison with 5-6 in non-polar solvents. [JPP-2007, 59, 29-39.] 19
  20. 20. METHODS OF MODIFICATIONS OF CRYSTAL HABITExcessive super saturation. E.g. transform a prism orisodiametric crystals to needle shape.Cooling rate and agitation. E.g. naphthalene gives thin platesif rapidly cooled whereas slow evaporation yields prisms.The crystallizing solvent. E.g. resorcinol produces needlesfrom benzene and squat prisms from butyl acetate.Addition of co-solvents or solutes. E.g. sodium chloride iscubic but urea produces octahedral habit. Crystal habit can also be modified by addingimpurities or „poisons‟; for example, sulphonic acid dyes alterthe crystal habit of ammonium, sodium and potassiumnitrates. 20
  21. 21. CHARACTERIZATION OF HABITS The angle between two crystals faces can be described in two ways: Included or edge angle between two faces, Interfacial or polar angle, the angle between the normals to the faces of the crystal. Interfacial angle is of importance in crystallography. They are measured by instruments known as goniometers. 21
  22. 22. CRYSTALLIZATION Crystallization is a chemical solid-liquid separation technique, in which mass transfer of a solute from the liquid solution to a pure solid crystalline phase occurs. The crystallization process consists of two major events: Nucleation Homogenous Heterogeneous Crystal growth 22
  23. 23. Super saturation is the driving force of the crystallizationThis can be achieved by various methods, with1) solution cooling,2) addition of a second solvent to reduce the solubility of the solute (technique known as anti-solvent or drown-out)3) chemical reaction4) change in pH being the most common methods used in industrial practice. Other methods, such as solvent evaporation, can also be used. 23
  24. 24. IMPORTANCE OF CRYSTALLINITY IN PREFORMULATION STUDIESEFFECT ON SOLUBILITY & BIOAVAILABILITYAntibiotic novobiocin is inactive in crystalline form whileamorphous form has 10 times more solubility and hence morebioavailable. 24
  25. 25. CHEMICAL STABILITY At instances crystalline form are more stable than amorphous form. e.g. crystalline forms of penicillin G as potassium or sodium salt are more stable. SUSPENSION SYRINGEABILITY A suspension of plate shaped crystals may be injected through a needle with a greater ease than one with needle shaped crystals of same dimensions. 25
  26. 26. EFFECT ON GRANULATION Sulphathiazole can exist in different crystalline forms . Form III has water adsorption of 0.046 mg/m2 & form I has water adsorption of 0.031 mg/m2 so form III shows better wetting and so easy granulation. Use of amorphous form of calcium pentothenate in multi- vitamin tablets prepared by wet granulation process, is not desirable because polymorphic transformation makes the granulation mass sticky, making further granulation virtually impossible. 26
  27. 27. HARDNESS OF TABLET Sulphamerazine is available in two different crystalline forms SMZ-I & SMZ-II. SMZ-I forms harder tablets than SMZ-II at same compression pressure and so it shows delayed release. 27
  28. 28. POLYMORPHIC TRANSFORMATION Many drugs undergo polymorphic transformation during various processes. E.g. during grinding drugs like digoxin, estradiol, spironolactone, phenylbutazone undergo transformation. By granulation of theophylline with water converts into monohydrate from anhydrous form. Similarly by drying and compression also drugs undergo change in their form. 28
  29. 29. LATEST TECHNIQUE DEVELOPMENTS IN CRYSTALLIZATIONSPHERICAL CRYSTALLIZATION- It has been developed by Yoshiaki and co-workers. It is a solvent exchange crystallization method in which crystal agglomeration is purposefully induced through the addition of third solvent termed as “Bridging liquid” which act as granulating agent. 29
  30. 30. It is a novel technique . to improve compressibility, good flow ability and bioavailability of pharmaceuticals. Moreover tablets formed have greater mechanical strength and lower friability. Various drugs have been successfully undergone this process to acquire improved micromeritic properties and thus have shown increased dissolution rate like salicylic acid, mefenemic acid, aminophylline, tolbutamide. [Pharmaceutical Research-1994, 11(4)] 30
  31. 31. METHODS OF SPHERICAL CRYSTALLIZATION SIMPLE SPHERICAL CRYSTALLIZATION E.g. spherical crystallization of salicylic acid from ethanol by addition of water, using chloroform as bridging unit. QUASI-EMULSION-SOLVENT-DIFFUSION METHOD E.g. antirheumatic drug bucillamine was crystallized as spheres by this method using HPMC. Also controlled release microspheres of ibuprofen with acrylic polymers was accomplished by this method. AMMONIA DIFFUSION METHOD Useful for amphoteric drugs like enoxacin. NEUTRALIZATION METHOD Tolbutamide dissolved in sodium hydroxide and HPEC aqueous solution was crystallized using this method. 31
  32. 32. SUPER CRITICAL FLUID CRYSTALLIZATION It is a novel technique used for selective production of polymorphs and pseudo polymorphs from aqueous solution. CHIRAL DRUGS Resolution of chiral drugs and drug intermediate is done by preferential crystallization. 32
  33. 33. POLYMORPHISMLIST OF CONTENTS : Definition Need to study polymorphism Types Transition temperature How to differentiate them Pseudo polymorphism How to differentiate pseudo polymorphs from true polymorphs? Methods to identify polymorphism Parameters to be cared by preformulator Properties Stability of metastable polymorph Factor affecting polymorphism Effect of polymorphism on bioavailability 33
  34. 34. Ability of any compound or element to crystallize as more than one distinct crystal species with different Internal lattice. Example:- Carbon --- cubic: diamond ---Hexagonal: graphite The term polymorphism was coined by AGUIAR ETAL in 1967 34
  35. 35. NEED TO STUDY POLYMORPHISM  Show the same properties in the liquid or gaseous state but they behave differently in the solid state.  Polymorphism is remarkably common particularly within certain structural groups. For e.g. class % of polymorphs Barbiturates 63 Steroids 67 Sulfonamides 40 35
  36. 36.  The effect of polymorphism on bioavailability is the most important consequence for drug substances if the bioavailability is mediated via dissolution. Examples:- chloramphenicol palmitate. noviobiocine griseofulvine Carbamazepine aspirin ampicillin The polymorphism of the excipients may also play an important role in bioavailability. Polymorphic behavior of drugs and excipients is an important part of the preformulation work. 36
  37. 37. TYPES PHASE TRANSITION: process of transformation of one polymorph into another, which may also occur on storage or during processing is called phase transition. ENANTIOTROPHS :-phase transition is reversible that means metastable↔stable . E.g.sulfur MONOTROPHS:-phase transition occurs only in one direction that means metastable→stable.eg. glyceryl stearate. 37
  38. 38. TRANSITION TEMPERATURE  “Temperature at which both stable and metastable forms exist in equilibrium with each other.”  In case of monotropy higher melting form is always thermodynamically stable form.  In case of enantiotropy lower melting form is thermodynamically stable at the temperature below the transition temperature and higher melting form is stable at the temperature above the transition temperature 38
  39. 39. HOW TO DIFFERENTIATE THEM• Differentiated by vapor pressure versus temperature curve and solubility versus temperature curve. Here form I is stable at temperature T1 and if it exist in form I&II, the phenomena is called enantiotrophism. In case of enantiotrophism transition temperature of both the forms are same. A different situation exists if compound exists as form III. Such phenomena is referred as monotrophism. Here transition temperature of both the forms are different since form III is relatively unstable than form I. 39
  40. 40. PSEUDOPOLYMORPHISM The term pseudo means false. Phenomenon in which solvent molecules get incorporated into crystal lattice of solid are known as solvates. These solvates exist in different crystal form called pseudo polymorphs and the phenomenon is called as pseudo polymorphism. Also known as hydrates when water is solvent. E.g. when the potent synthetic estrogen ‘ethynylestradiol’ is crystallized from the solvents acetonitrile, methanol, chloroform and saturated with water; four different crystalline solvates are formed. 40
  41. 41. HOW TO DIFFERENTIATE PSEUDOPOLYMORPHSFROM TRUE POLYMORPHS? Melting behavior in silicon oil using HOT STAGE MICROSCOPY. Pseudo polymorphs--- evolve gas (steam or solvent vapors) causing bubbling of the oil. True polymorphs--- merely melts, forming second globular phase. 41
  42. 42. METHODS TO IDENTIFY POLYMORPHISM Optical crystallography Hot stage microscopy X-ray diffraction method NMR technique FTIR Dilatometry Microcalorimetry Thermal methodsA)DSC [differential scanning calorimetry]B)DTA [differential thermal analysis]C)TGA [thermal gravimetric analysis] Measures heat loss or gain from physical or chemical changes occurring in sample which is recorded as a function of temperature. Melting point determination 42
  43. 43. PROPERTIES show the same properties in liquid or gaseous state but they behave differently in solid state. differ from each other with respect to physical properties like Melting and sublimation temperature Vapour pressure Solubility and dissolution rate Stability Optical and electrical properties Crystal habit Hygroscopicity Heat capacity Solid –state reactions Conductivity Compression characteristics etc.. 43
  44. 44. 1)stability characteristics:-If a compound exist polymorphism, one of the form will be more stable (physically) than the other form. Depending upon relative stability there are two forms of polymorphs: a) stable form having lowest energy state, highest melting point and least aqueous solubility. b)Metastable form having higher energy state, lower melting point and higher aqueous solubility. 44
  45. 45. CONTINUED…2)Relative solubility of polymorphs:-In order to assess the relative increase in solubility of polymorphs with respect to another, a simple solubility ratio can be defined:- solubility ratio =solubility of metastable form solubility of stable form Examples:- Aspirin-1.2 Carbamazepine-1.2 Indomethacine-1.4 Tetracycline-1.6  From above example, we can say that solubility ratio is higher than one just because of relative higher solubility of metastable form, which leads to increase in apparent solubility. 45
  46. 46. 3)Dissolution behavior of the polymorphs:- The absorption rate and bioavailability of drug administered orally is controlled by many factors among which dissolution rate is one of the most important. Therefore physicochemical state such as polymorphism or amorphism of drugs affect bioavailability of pharmaceutical preparation. Amorphous>metastable> stable 46
  47. 47. FACTOR AFFECTINGPOLYMORPHISM (A)Temperature and humidity:-  Storage conditions affect physicochemical reactions which are accelerated at higher temperature.(Arrhenius theory).  Humidity act as catalyst on the solid surface. Therefore both are the important factors for the prefomulator scientist to consider.  E.g. 1. chlortetracycline hydrochloride has two different polymorphs forms: α and ß. Alpha form is stable up to 82% RH while beta form is hygroscopic. 2.polymorphic transformation of phenylbutazone and cocoa butter occur after heating. 47
  48. 48. (B)Photostability:- Generally light sensitive drugs are protected from the photolytic degradation by packing them suitably in light resistant container. However the bulk powder of the stable crystalline forms resists photochemical degradation and do not require light resistant system. But still there are fewer reports: For e.g. five different polymorphic form of 21-tert-butyl acetate out of which form 1 and 4 are unstable under U.V. light while form 2 ,3 and 5 were stable.(C) Effect of solvent:- Solvent can bring dramatic change in growth mechanism and morphology. Growth kinetic of crystal growing from solution was determined by two important factors:  Degree of molecular roughness  Nature of absorption of the solvent from surface. 48
  49. 49. (D)Effect of grinding:- Grinding process reduce particle size ,so increasing specific surface area and that’s why direct effect on dissolution rate and bioavaibility of the preparation. During grinding process solid state polymorphic transformation in to non-crystalline or metastable form is caused by mechanical action.. E.g. prasterone sulfate dehydrate Here dehydrate form was more stable than anhydride form. with increasing grinding time, water content compound become unstable because grinding weakened bonding crystals and water molecules participating in hydrolysis process of the drug. 49
  50. 50. (F)Effect of surfactant:- Surfactant affect solution mediated transformation of the drug which depends on molecular and supramolecular structure of the drug. eg.carbamazepine has two different polymorphic forms :-anhydrous and dehydrate. Here dehydrate form has higher dissolution rate. In SLS increase growth of dehydrate form while in case of poloxamer , polysorbate 80 decrease growth of dehydrate form. 50
  51. 51. EFFECT OF POLYMORPHISM ON BIOAVAILABILITY  If the absorption of active ingredient in drug through G.I.T. is dissolution rate dependent then polymorphism is an important preformulation tool.  Here successful utilization of polymorph having significant greater thermodynamic activity (solubility)may provide good therapeutic blood level from otherwise inactive drugs  E.g. novobiocin, identified in two different forms: crystalline and amorphous. In tablet or capsule formulation novobiocin is used as sodium salt which is active orally but unstable chemically while insoluble form is stable chemically and orally inactive (unabsorbable). 51
  52. 52. VARIOUS CHARACTERIZATION TECHNIQUESUSED IN PREFORMULATION LIST OF CONTENTS :  Differential thermal analysis (DTA)  Differential scanning calorimetry (DSC)  X-ray diffraction  Fourier transform infrared spectrophotometry (FTIR)  Other thermal techniques  Innovation in thermal analysis 52
  53. 53. Differential Thermal analysis (DTA)PRINCIPLE: A Technique in which the temperature difference between a substance & a reference material is measured as a function of temperature, while the substance & reference are subjected to a controlled temperature programmed. The Difference in temperature is called as Differential temp(∆T) is plotted against temp. or a function of time. 53
  54. 54. Endothermic Peak:An endothermic peak, is a peak where thetemperature of the sample fallsbelow that of the referencematerial, i.e., ∆T is negative.Exothermic peak: An exothermic peak, is a peak where thetemperature of the sample rises above thatof the reference material, i.e. ∆T is positive. 54
  55. 55. APPLICATIONS : DTA is particularly useful in preformulation studies including purity, polymorphism, solvation, degredation & excipient compatability. It measures physical or chemical changes of drug molecules. 55
  56. 56. Differential scanning calorimetry (DSC)PRINCIPLE: It is a technique in which the energy necessary to establish a zero temp. difference between the sample & reference material is measured as a function of temp. DSC Is widely used to measure glass transition temp & characterization of polymer. Glass Transition temp(Tg): Temp at which an amorphous polymer or an amorphous part of crystalline polymer goes from hard ,brittle state to soft, Rubbery state. 56
  57. 57. Types of reaction ENDOTHERMIC EXOTHERMICPhysical reaction Chemical reaction e.g vaporisation e.g vaporisation Oxidation, Oxidation, Sublimation, Sublimation, catalytic reaction, catalytic reaction, absorption absorption polymerization polymerization 57
  58. 58. INSTRUMENT OF DSC 58
  59. 59. Ideal DSC curve: 59
  60. 60. APPLICATIONS : DSC is best method for detection of impurity. DSC is also used in drug excipient compatability study. e.g. DSC of sparfloxacin• DSC is used in study of polymer. 60
  61. 61. 61
  62. 62. GENERAL PRINCIPLE & APPLICATION OF FT IR SPECTRUM & X-RAYDIFFERACTION METHOD. FT IR:  New technique in preformulation.  Generally used in combination with other technique. 62
  63. 63. ADVANTAGE: - Simple - Sensitive - Accurate - SpeedyDISADVANTAGE: 1) Generally not used alone. 2) Gives peak at same wave number, e.g so not differentiate polymorph. 63
  64. 64. B)X-RAY POWDER DIFFERACTION Why only x-ray are used? Because x-rays have wavelengths of about the same magnitude as the distance between the atoms or molecules of crystal.PRINCIPLE: x-ray are Diffracted & order of this diffraction is measured in form of graph. Diffraction occur as a result of the interaction of radiation with electron of atom. 64
  65. 65. Application 0f x-ray diffraction1)For structure determination:2)Identification Of Impurity:3)Characterization of polymorphism:4) Characterize spray dried & crystalline material.5)For particle size analysis. 65
  66. 66. OTHER THERMAL TECHNIQUES : 1) Thermo photometry: 2) Thermo luminescence: 3) Thermo microscopy: 4) Micro thermal analysis: 5) Differential mechanical analysis: 6) Emanation thermal analysis: 7) Thermo particulate analysis: 66
  68. 68. GTU QUESTIONS Define polymorphism and pseudo-polymorphism. Enlist the methods to identify polymorphism. Comment on dissolution behavior and stability of polymorphs. What is polymorphism? What is its significance in dissolution and patenting? Name the methods to identify polymorphs. 68
  69. 69. REFERENCES Pharm. Dosage forms and drug delivery system , ANSEL, 100,151. Pharm. Dosage forms, LACHMANN and LIBERMANN, 1, 26-30. Modern pharmaceutics, BANKER,MARSHALL DEKKER INC. Pharm Encyclopedia, 3, 399. Pharm Encyclopedia, 12, 320-321. Advanced pharmaceutical solids, CARSTENSEN, 110, 6. Physical pharmacy, ALFRED MARTIN. Industrial pharmacy, LACHMANN and LIBERMANN. Physico-chemical principles of pharmacy, A.T.FLORENCE & D.ATTWOOD, 8-10. 69
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