Preformulation studies

Transcription

1 2.1. PREFORMULATION AND STANDARDIZATION Preformulation is an exploratory activity that begins early in drug development. are designed to determine the compatibility of initial excipients with the active substance for a biopharmaceutical, physicochemical, and analytical investigation in support of promising experimental formulations. Data from preformulation studies provide the necessary groundwork for formulation attempts. The selected drugs and excipients were standardized as per respective pharmacopoeial specifications, wherever applicable. Excipients which were not official in pharmacopoeias were standardized as per the manufacturers specifications. The certificates of analysis provided by the suppliers in case of gift samples have been duly included in the appropriate sections. Telmisartan and Cefpodoxime proxetil used in this project were a generous gift sample by Glenmark Generics Ltd.,Ankleshwar and Maxim Pharmaceuticals Pvt.Ltd., Pune respectively. Vitamin E TPGS was provided by Isochem, France and Capmul MCM was provided by Abitec Corporation, USA as gift sample.espheres (18-20#/Microcrystalline cellulose pellets) were provided by Ideal Cures Pvt.Ltd.,Mumbai. All other excipients were procured locally from S.D.Fine Chemicals Telmisartan (TEL) Structure: IUPAC Name: 2-[4-[[4-methyl-6-(1-methylbenzimidazol-2-yl)-2-propylbenzimidazol-1- methyl]phenyl]benzoic acid Solubility enhancement of BCS Class II/IV drugs 42

2 Molecular Formula: C 33 H 30 N 4 O 2 Molecular Weight: Characteristics: Telmisartan is a BCS class II drug having poor solubility and good permeability. It is a white or slightly yellowish, crystalline powder. The properties of TEL are enlisted in Table Table Evaluation of TEL Sr.No. Test Specifications Results 1. Appearance White or slightly yellowish crystalline powder Complies 2. Melting C 265 C point 3. Solubility Practically insoluble in water, slightly soluble in methanol, sparingly soluble in methylene chloride. Dissolves in 1 M sodium hydroxide. Complies 4. Identification IR spectrophotometry See Figure Characterization of TEL: TEL was characterized in terms of UV, FTIR spectra and DSC thermogram. A.UV Visible Spectroscopy: In order to confirm λmax of TEL, 10 µg/ml solution was analyzed at spectrum measurement by double beam spectrophotometer (Jasco V-550, Japan) against methanol as a blank. The UV spectrum is shown in Figure TEL showed maximum absorption [λmax] at 296nm. Figure UV spectrum of TEL Solubility enhancement of BCS Class II/IV drugs 43

3 B. FT-IR Spectroscopy: The IR spectra of TEL was recorded using Fourier Transform Infra-Red spectrophotometer (450 plus, Jasco- Japan) with diffuse reflectance principle. The spectrum was scanned over a frequency range cm -1. The FT-IR spectrum of TEL is shown in Figure The characteristic peaks for TEL can be observed at wavenumbers 3673 cm -1 [due to free O-H stretching vibrations], 1695cm -1 [C=O stretching vibrations], cm -1 [C-N stretching vibrations] and 1455 and 1381[CH 3 bending vibrations]. Figure FT-IR spectra of TEL C. DSC thermograms: The DSC thermogram was recorded using Differential scanning calorimeter (DSC 823e, Mettler Toledo, Japan). Thermal data analysis of the DSC thermogram was conducted using STARe software (version 5.21) and the thermogram is depicted in Figure A sharp endotherm was recorded at 265 C, which is the melting point of TEL. Figure DSC thermogram of TEL Solubility enhancement of BCS Class II/IV drugs 44

4 Cefpodoxime proxetil (CP) Structure IUPAC Name: 5-Thia-1-azabicyclo[4.2.0]oct-2-ene carboxylic acid, 7-[[(2-amino-4-thiazolyl) (methoxyimino)acetyl]amino]-3-(methoxymethyl)-8-oxo-,1- [[(1methylethoxy)carbonyl]oxy] ethylester, [6R-[6 α 7 β Z)]]- (+-)-1-hydroxyethyl(+)-(6R, 7R)-7-[-(2-(2-animo-4-thiozolyl) glyoxylamido]-3-methoxymethyl)-8-oxo-5-thia-1- azabicyclo[4.2.0]oct-2-ene-carxylate, 7-(z) O-methyloxime)isopropyl carbonate(ester) Molecular Formula : C 21 H 27 N 5 O 9 S 2 Molecular weight : Characteristics: CP is a BCS class IV drug having poor solubility and poor permeability. It is a slightly yellowish, crystalline powder. The properties of CP are enlisted in Table Table Evaluation of CP Sr.No. Test Specifications Results 1. Appearance White or slightly yellowish crystalline powder Complies 2. Melting C 88 C point 3. Solubility Poorly soluble in water (400µg/ml), Very soluble in methanol, slightly soluble in ether, freely soluble in ethanol Complies 4. Identification IR spectra Complies 5. Specific rotation Between +35 and Solubility enhancement of BCS Class II/IV drugs 45

5 Characterization of CP CP was characterized in terms of UV, FTIR spectra and DSC thermogram. A. UV Visible Spectroscopy: To confirm the λmax of CP, 10 µg/ml solution was analyzed at spectrum measurement by double beam spectrophotometer (Jasco V-550, Japan) against methanol as a blank. The UV spectrum is shown in Figure CP showed maximum absorption [λmax] at 263 nm Abs Wavelength[nm] Figure UV spectrum of CP B. FT-IR spectroscopy: The FT-IR spectrum of CP showed the characteristic peaks for CP at wavenumbers 1274cm -1 [due to C-O stretching vibrations], 1759 cm -1 [C=O stretching vibrations], 1271cm -1 [C-N stretching vibrations], 1676 cm -1 [C= N stretch], 3322 cm -1 [N- H stretch] and 2819 cm -1 [S-H stretch]. (Figure 2.1.5) Solubility enhancement of BCS Class II/IV drugs 46

6 %T Chapter Wavenumber[cm-1] Figure FT-IR spectra of CP C. DSC thermogram: The thermogram of CP exhibited a weak endotherm at 88 C which is the melting point of CP. There was no evidence of any other undesirable thermodynamic phase transformations (Figure 2.1.6). ^exo Cefpodoxime poxetil, :15:19 Cefpodoxime poxetil, mg 5 mw Experiment: Cefpodoxime poxetil, :43: C min Lab: METTLER STAR e SW Figure DSC thermogram of CP Solubility enhancement of BCS Class II/IV drugs 47

7 VITAMIN E TPGS NF Grade Structure: IUPAC name: Poly(oxy-1,2-ethanediyl),α-[4-[[(2R)-3,4-dihydro-2,5,7,8-tetramethyl-2-[(4R,8R)-4,8,12- trimethyltridecyl]-2h-1-benzopyran-6-yl]oxy]-1,4-dioxobutyl]-α-hydroxy- Molecular Formula: C 33 O 5 H 54 (CH 2 CH 2 O)n Molecular Weight: 1513 (approx) Characteristics: Vitamin E TPGS is water-soluble waxy solid with low melting point. It has amphiphilic properties with a polar hydrophilic head (polyethylene glycol 1000) and a lipophilic tail (phytyl chain of d-α-tocopherol) and HLB value of 13. Table Evaluation of Vitamin E TPGS Sr.No. Test Specifications Results 1. Appearance Light tan waxy solid Complies 2. Melting 38 C 38 C point 3. Solubility Up to 20 g/ 100ml of water at room temperature Complies 4. Viscosity cps at 50 C Complies 5. Critical Micellar concentration 0.02 weight % at 37 C Complies Solubility enhancement of BCS Class II/IV drugs 48

8 FT-IR spectra: FT-IR spectra of TPGS displayed the characteristic peaks: C=O overtone at 3427 cm -1, CH stretch at 2528 cm -1, C=O stretching vibrations at 1745 cm -1, C-O stretch at 1100 cm - 1,and vibrations due to substituted benzene at 774 cm -1. (Figure 2.1.7) %T Wavenumber [cm-1] Figure FT-IR spectra of Vitamin E TPGS Polyethylene glycol 6000 Structure: IUPAC Name: Poly (oxy-1,2-ethanediyl),α-hydro-ω-hydroxy-polyethylene glycol Molecular Formula: C 17 H 33 COO (CH 2 CH 2 O) n H where n represents the average number of oxyethylene groups. Molecular weight: Solubility enhancement of BCS Class II/IV drugs 49

9 Characteristics: PEG 6000 is a white to creamy white, wax-like solid or flakes with a faint and characteristic odor. Table Evaluation of PEG 6000 Sr.No. Test Specifications Results 1. Appearance Creamy white waxy solid Complies 2. Melting 38 C 38 C point 3. Solubility Soluble in acetone, dichloromethane, ethanol (95%), Complies and methanol;freely soluble in water 4. ph ,determined in a 5% w/v solution Complies FT-IR spectra: The typical peaks that were evident in the FT-IR spectra of PEG 6000 included C-H stretch at 2887 cm -1, C-O stretch at 1100 cm -1 & O-H stretching vibrations at 3600 cm -1. (Figure 2.1.8) %T Wavenumber[cm-1] Figure FT-IR spectra of PEG 6000 Solubility enhancement of BCS Class II/IV drugs 50

10 Polyvinyl pyrrolidone K30 (Povidone) Structure: IUPAC Name:1-Ethenyl-2-pyrrolidinone homopolymer Empirical formula: (C 6 H 9 NO)n Molecular weight: (approx.) Characteristics: Povidone occurs as a fine, white to creamy-white colored, odorless or almost odorless, hygroscopic powder. Povidones with K-values equal to or lower than 30 are manufactured by spray-drying and occur as spheres Table Evaluation of PVPK 30 Sr.No. Test Specifications Results 1. Appearance Yellowish brown powder Complies 2. Melting Softens at 150 C Complies point 3. Solubility Freely soluble in acids, chloroform, ethanol (95%), Complies ketones, methanol, and water; practically insoluble in ether, hydrocarbons, and mineral oil. 4. ph ,determined in a 5% w/v aqueous solution Complies Solubility enhancement of BCS Class II/IV drugs 51

11 FT-IR spectra: The characteristic peaks displayed in the IR spectra of PVPK 30 included N-H stretch at 3648 cm -1, C=O at 1847 cm -1, CH 2 bending at 1457 cm -1,C-N stretch at 1419 cm -1 and CH 3 bending at 1271 cm -1.(Figure 2.1.9) %T Wavenumber[cm-1] Figure FT-IR spectra of PVPK Poloxamer 188 Structure: Molecular formula: Hydro-hydroxypoly (oxyethylene) a poly (oxypropylene) b poly(oxyethylene) a block copolymer in which a and b have values of 80 and 27, respectively. Average molecular weight: 7680 to 9510 Characteristics: The polymers are block copolymers of polyoxyethylene-polyoxypropylene. The average particle size is approximately 50 μm. It is white microprilled powder with a weak odor. Solubility enhancement of BCS Class II/IV drugs 52

12 The products also contain approx. 100 ppm BHT. Table Evaluation of Poloxamer 188 Sr.No. Test Specifications Results 1. Appearance White microprilled powder with a weak odor Complies 2. Melting 52 C Complies point 3. Solubility Readily soluble in water and ethanol (95%) and other mainly polar solvents. They are insoluble in ether, paraffin and fatty oils. Complies FTIR spectra: The prominent peaks evident in the IR spectra of Poloxamer 188 included O-H stretch at 3467 cm -1, CH stretch at 2887 cm -1,O-H at 1343 cm -1,C-O at 1124 cm -1 and (CH3) 2 C-O at 1320 cm -1.(Figure ) %T Wavenumber [cm-1] Figure FTIR spectra of Poloxamer 188 Solubility enhancement of BCS Class II/IV drugs 53

13 β-cyclodextrin: Structure: Empirical formula: C 42 H 70 O 35 Molecular weight: 1135 Characteristics: CDs are cyclic oligosaccharides containing at least six D-(+)-glucopyranose units attached by α(1 4) glucoside bonds. β-cds contain 7 glucose units, respectively. CDs occur as white, practically odorless, fine crystalline powders, having a slightly sweet taste. Some CD derivatives occur as amorphous powders. Table Evalaution of β- cyclodextrin Sr.No. Test Specifications Results 1. Appearance A white or almost white, amorphous or crystalline powder Complies 2. Melting C 258 C point 3. Solubility Soluble 1 in 200 parts of propylene glycol, 1 in 50 of water at 20 C, 1 in 20 at 50 C; practically insoluble in acetone, ethanol (95%), and methylene chloride. Complies Solubility enhancement of BCS Class II/IV drugs 54

14 FT-IR spectra: The prominent peaks evident in the IR spectra of β-cd included C-O-C stretch at 1032 cm -1, H-O-H bending at 1647 cm -1, O-H at 3412 cm -1,C-H stretch and C=O at 1651 cm %T Wavenumber[cm-1] Figure FT-IR spectra of β-cd Diphenyl carbonate: Structure: Molecular Formula: C 13 H 10 O 3 Molecular Weight: g/mol. Characteristics: DPC occurs as a white, flaky solid. Table Evaluation of DPC Sr.No. Test Specifications Results 1. Appearance White flaky solid Complies 2. Melting 78.8 C 78 C point 3. Solubility Soluble in ethanol, diethyl ether, carbon tetrachloride, acetic acid Complies Solubility enhancement of BCS Class II/IV drugs 55

15 Sodium bicarbonate: Chemical Name: Carbonic acid monosodium salt Empirical Formula: NaHCO 3 Molecular Weight: Characteristics: Sodium bicarbonate occurs as an odorless, white, crystalline powder with a saline, slightly alkaline taste. The crystal structure is monoclinic prisms. Grades with different particle sizes, from a fine powder to free-flowing uniform granules, are commercially available. Table Evaluation of NaHCO 3 Sr.No. Test Specifications Results 1. Appearance Odorless, white crystalline solid Complies 2. Melting 270 C Complies point 3. Solubility Practically insoluble in ethanol (95%) and Complies ether,solubility in water is 1 in ph 8.3 for a freshly prepared 0.1 M aqueous solution at 25 C Capmul MCM Chemical name: Glyceryl mono-dicaprylate 1,2,3-Propanetriol Average Molecular weight: 277 Description: Capmul MCM is a blend of medium-chain mono-, di-, and triglycerides (58% monoglyceride, 36% diglyceride, and 5% triglyceride consisting of 80% w/w caprylic acid (C8), 20% capric acid (C10), and 2% caproic acid (C6). Solubility enhancement of BCS Class II/IV drugs 56

16 Table Evaluation of Capmul MCM Sr.No. Properties Specifications Results 1. Physical state Soft solid or liquid Complies 2. Appearance Slightly brown colored Complies 3. HLB 5 Complies 4. Solubility in water Partially soluble Complies 5. Specific gravity 0.95 at 25 C Viscosity 23 Cps. at 25 C 22.5 cps 7. Density g/cm g/cm Tween 80 (Polysorbates 80) Structure: Empirical Formula: C 64 H 124 O 26 Molecular Weight: 1310 Characteristics: Polysorbates have a characteristic odor and a warm, somewhat bitter taste. Polysorbate 80 is a yellow oily liquid. Solubility enhancement of BCS Class II/IV drugs 57

17 Table Evaluation of tween 80 Sr.No. Test Specifications Results 1. Appearance Yellow, oily liquid Complies 2. HLB 15 Complies 3. Solubility Soluble in ethanol & water, insoluble in mineral Complies &vegetable oil 4. ph 6-8 for 5%w/v aqueous solution Complies 5. Viscosity 425 mpas Complies 6. Specific 1.07 at 25 C Complies gravity 7. CMC 0.012mM at room temperature Complies Solubility enhancement of BCS Class II/IV drugs 58

18 RESULTS: The standardization of drugs and excipients is an integral part of any research work and ensures quality of the research outcomes. Telmisartan was standardized as per the specifications given in the monograph in BP 2009.Table enlists the various tests, observations and specifications. The drug passed all the tests for identity and was well within pharmacopoeial limits. The FT-IR spectra and DSC thermogram are shown in Figures and The COA provided by the Glenmark generics is also attached.[appendix 4] Cefpodoxime proxetil was standardized as per the specifications given in the monograph in USP Table enlists the various tests, observations and specifications. The drug passed all the tests for identity and was well within pharmacopoeial limits. The FT-IR spectra and DSC thermogram are shown in Figures and The COA provided by the Maxim Pharmaceuticals Ltd., is also attached.[appendix 4] Vitamin E TPGS was standardized as per the specifications enlisted on the Isochem website (Table 2.1.3).The IR spectra is displayed in Figure The COA provided by the company is also included.[appendix 4] PEG 6000 was standardized as per the specifications of IP Table enlists the various tests, observations and specifications. The polymer passed all the tests for identity and was well within pharmacopoeial limits. The FT-IR spectrum is shown in Figure PVPK30 was standardized as per the specifications of USP 30. Table enlists the various tests, observations and specifications. The polymer passed all the tests for identity and was well within pharmacopoeial limits. The FT-IR spectrum is shown in Figure Poloxamer 188 was standardized as per the specifications of USP 30. Table enlists the various tests, observations and specifications. The polymer-surfactant passed all the tests for identity and was well within pharmacopoeial limits. The FT-IR spectrum is shown in Figure Solubility enhancement of BCS Class II/IV drugs 59

19 β-cyclodextrin was standardized as per the specifications of USP 30. Table enlists the various tests, observations and specifications. The excipient passed all the tests for identity and was well within pharmacopoeial limits. The FT-IR spectrum is shown in Figure Diphenyl carbonate was standardized as per the supplier s specifications. Table enlists the various tests, observations and specifications. The cross-linking agent passed all the tests for identity and was well within pharmacopoeial limits. Sodium bicarbonate was tested as per specifications given in IP Its properties are listed in Table and it was found to obey the pharmacopoeial specifications. Capmul MCM was provided as gift sample and the COA is attached.[appendix 4] Table enlists its various properties and the sample provided fulfilled all requirements. Tween 80 was standardized as per the specifications of USP 30. Table enlists the various tests, observations and specifications. The surfactant passed all the tests for identity and was well within pharmacopoeial limits. The standardized drugs and excipients were used in different permutations to develop various formulations for enhancing their solubility as described in the following chapters. Solubility enhancement of BCS Class II/IV drugs 60

20 2.2. COMPATIBILITY STUDIES BETWEEN DRUG AND EXCIPIENTS The physical mixtures of drugs with excipients (1:1) were prepared by mixing required amount of TEL/CP and excipients for 5 minutes in a mortar with the help of spatula. This mixture was sieved through a 60 mesh screen. TEL was evaluated for compatibility with β-cd, NS, Sodium bi-carbonate, poloxamer 188, TPGS, PEG 6000 and PVPK30.CP was evaluated for compatibility with NS, poloxamer 188, TPGS, PVPK30, Capmul MCM and tween 80.The mixtures were subjected to accelerated stability condition (40 C and 75% relative humidity) for 1 month. The mixtures were analyzed by FTIR for compatibility. RESULTS: i] Compatibility between TEL and excipients: Physical evaluation of the binary mixtures of TEL and excipients used in formulation of nanosponges and nanocrystals revealed no discoloration or other apparent signs of degradation. The IR spectra recorded at the end of the evaluation period exhibited no gross changes such as appearance of additional peaks or disappearance of the characteristics peaks. Insignificant shifting or reduction in intensity of peaks was observed which was due to dilution effect in the mixture. Figures display the spectra of mixtures of TEL with excipients used in nanosponge and nanocrystal formulations kept under accelerated conditions. Figure IR spectra of A= TEL; B= β- CD;C = NS Solubility enhancement of BCS Class II/IV drugs 61

21 Figure A=TEL,B= PVPK30, Figure A=TEL,B= PEG 6000 C=TEL-PVP C=TEL-PEG6000 Figure IR spectra of A=TEL,B=P188, C=TEL-P188 Figure IR spectra of A=TEL, B= TPGS,C=TEL-TPGS Solubility enhancement of BCS Class II/IV drugs 62

22 ii] Compatibility between CP and excipients: CP was subjected to compatibility studies with excipients used in formulation of nanosponges, nanoparticles and self-microemulsifying drug delivery systems. No physical changes indicative of degradation were apparent in the physical mixtures at the end of evaluation period. The IR spectra also displayed no significant changes thereby indicating the compatibility between CP and the excipients. (Figure ). Figure IR spectra of A=CP, B=NS, C=CP-NS Solubility enhancement of BCS Class II/IV drugs 63

23 Figure IR spectra of A=CP, B=CP-Capmul MCM, C=CP-tween 80,D=CP-TPGS Figure IR spectra of A=CP, B=CP-P188, C=CP-TPGS The selected excipients were found to be compatible with TEL and CP displaying no obvious signs of degradation on visual observation which was further corroborated by the IR spectra of the physical mixtures. Hence further experimentation for formulation development using these excipients could be initiated. Solubility enhancement of BCS Class II/IV drugs 64