Preformulation Testing for Chemical Properties of Drug

Preformulation Testing for Chemical Properties of DrugPREFORMULATION STUDIESPreformulation testing involved investigation of physical and chemical properties of a window pane substance alone and when combined with excipients. It was the first step in the rational development of dosage forms.These stu travels are categorised as under1. API characterization2. Drug-Excipient Compatibility topicAPI CharacterizationOrgano(prenominal)eptic EvaluationThese are preliminary characteristics of every substance which is useful in identification of specific material. Following physical properties of API were studied.a) Colourb) Odour put over no. Characterization of APITestObservationColourWhiteOdourOdourlessParticle size distributionSieve outlineThe sieve analysis main concept is to know the disparate drug particles size in the sample. The standard sieves with larger pore size i.e., with less sieve number on the top position are placed one over the other and followed by sieves of decreasin g pore size i.e., with larger sieve number towards the bottom. mappingClean and dried sieves 40,60,80,100,120 and bottom operatees were collectedIndividual weight of each sieve was noted.These sieves were arranged in ascending order.Weighed quantity of API was placed in 40 meshes.Sieve shaker was set for 5 min at amplitude of 60.Remove the setup from sieve shaker after 5minutes.Each mesh was weighed individually and Calculate % retained in each size of mesh with following formula% retained = Final weight initial weight x 100 ingrained weight takenTable no. Particle size distribution of APISieve numberPercentage of sample retained (%) cumulative percentage of sample retained (%)403.03.06019.222.28026.348.510024.272.71408.180.820019.2100.0pH-Solubility ProfileThe solubility studies for the drug were carried out using the orbital shaker. Solubility of the drug across different cushions was studied. The pH ranged from 1.2 to 6.8 (1.2 , 4.5, 6.8, and water). All the buffers were prep ared according to USP 34 NF 29, 2011. Excess drug was added to 100 ml of water in stoppered conical flasks and were agitated continuously in a orbital shaker for 24 hrs at 200 rpm and room temperature (25 C), till vividness was observed. and then, the samples were filtered using 0.45 Nylon (47 mm) syringe filters. Now the filtered samples were analyzed using UV spectrophotometer Table No.6.3 below describes the procedure of buffers preparation.Table 6.5 preparation of buffersBuffer affairPH 1.2 buffer8.5 ml of Conc. HCL was added to molarity mL tawdrinesstric flask. Then it was diluted and made up to playscript with waterPH 4.5 phosphate buffer13.61 gm of KH2PO4 was added to 1000 mlvolumetric flask. Then it was made up to volumewith waterPH 6.8 phosphate buffer250 mL of 0.2 M monobasic potassium phosphate issue was taken in a 1000 mL volumetric flask. Then 112 mL 0.2M atomic number 11 hydroxide dissolving agent was added to it and water was added to make up to the volumeTab le7.3 Solubility of API in buffers of different pHs PHSolubility(mg/ml)1.242.364.544.966.80.80Water0.674 Fig 7.1 pH Solubility veer of APIDrug excipient compatibility studythither is always possibility of Drug excipient interaction in any formulation out-of-pocket to their intimate contact. It is also necessary to determine any possible interaction between excipients used in the formulation. This will also advise success of stability studies.Preliminary studiesMethod Physical observationCondition 40 2 o C and 75 5% RHProcedureDrug was mixed with excipients in 1 1 ratios as indicated in the Table 6.6These mixtures were kept in a 5ml glass vials and packed properly.In wry close method glass vials are closed with rubber stoppersThese vials are exposed to 25C /60 % RH 40C /75 % RH.Blend (1gm) was prepared and filled in vials. Observations for physical appearance were made at the end 4 weeks.S.NoEXCIPIENTSDRUG EXCIPIENT RATIO1 polyethyleneoxide112HPMCK100M113MCC114Cellulose aceta te115Sodiumchloride116citric acid117Sodium lauryl sulphate118Magnesium stearate119Talc11Table 7.4 Results of Drug-Excipient compatibility at 25oC/60% RHS.noExcipentColour changeLumpsCakingOCOCOC1Polyethylene oxideXXXXXX2HPMCXXXXXX3MCCXXXXXX4Cellulose acetateXXXXXX5Sodium chlorideXXLumps observedXXX6Citric acidXXLumps observedXXX7Sodium lauryl sulphateXXLumps observedXXX7Magnesium stearateXXXXXX8TalcXXXXXXNote x indicates no change, O- open precondition ,C- close conditionTable 7.5 Results of Drug-Excipient compatibility at 40oC / 75% RHS.noExcipientColour changeLumpsCakingOCOCOC1Poly ethylene oxideXXXXXX2HPMCXXXXXX3MCCXXXXXX4Cellulose acetateXXXXXX5Sodium chlorideXXXXCaking observedX6Citric acidXXXXCaking observedX7Sodium lauryl sulphateXXXXCaking observedX8Magnesium stearateXXXXXX9TalcXXXXXXFTIR StudyFTIR studyFTIR studies were carried out for unmixed drug alone and blend of drug excepients. The FTIR spectrographic analysis (BRUKER Optics FTIR spectrophotometer) is employed as analytical tool to check the drug-excepients interaction, using the KBr disc method. The FTIR spectra were scanned and recorded between cd and 4000 cm-1MethodNearly to a fine alkali halide (example KBr) powder of 200 to 250 mg 0.1 to 1.0 % sample is mixed well. Later it is pulverized and in a pellet-forming die it is placed. Around an 8 tons force under a vacuum of several mm Hg is applied to form transparent pellets.FTIR spectroscopy of unalloyed drug of FamotidineS.noType of vibrationActual frequency (cm-1)Observed frequency (cm-1)ConfirmationTable no. Interpretation of FTIR spectra of pure famotidineFTIR spectroscopy of drug and excipient blends Table 7.6 Peaks of FTIR studyPeaks ( cm 1)Functional groups3506.13OH3377.41-3400.95NH23238.03-NH1445.38- 1639.22C=N689.10 -606.6C-S1320.81S(=O) 2 asymmetric stretching1147.17S(=O) 2 symmetric stretchingTable no. Interpretation of FTIR spectra of pure famotidineS.noType of vibrationActual frequency (cm-1)Observed frequency (cm-1)Confi rmationANALYTICAL METHODESTIMATION OF FAMOTIDINEA radical of Famotidine was prepared in 0.1 N HCl and Phosphate buffer pH 4.5and 6.8 UV spectrum was taken using Perkin Elmer UV/Vis double beam spectrophotometer.The UV maxima of Famotidine was found to be 265 nm in both 0.1N HCl pH 4.5. In pH 6.8 it was found to be 268 nmPreparation of standard edit of famotidine in 0.1N HCL pH 4.5 phosphate buffer100 mg Famotidine each was dissolved in 0.1 N HCl and pH 4.5 buffer and volume is made up to 100 with respective buffer. 10 mL of stock solution (1mg/ml) was further diluted upto 100 ml with respective buffer to obtained solution of 100 g/mL.Now from stock 2 further dilutions were done with respective buffer to obtain solutions of 2, 5, 10, 15, 20 and 25 g/ml Absorbance of each solution was measured at 265 nm using Perkin Elmer UV/Vis double beam Spectrophotometer.Preparation of standard curve in ph 6.8 phosphate buffer10 mg Famotidine each was dissolved in pH 6.8 phosphate buffer and v olume is madeup to 100 ml to obtain solution of 100 g/ml. Now from this stock solution further dilutions were done with PH 6.8 to obtain solutions of 10 , 20 , 30 and 40 g/ml Absorbance of each solution was measured at 268 nm using Perkin Elmer UV/Vis double beam Spectrophotometer.The experiment was performed in triplicate and based on second-rate absorbance the equation for the best line was generated. The results of standard curve prepared in pH 1.2, 4.5 6.8 were shown belowTable 7.7 Standard curve of API in PH 1.2 , 4.5 6.8 buffers stringencyAbsorbance in pH 1.2Absorbance in pH 4.5Absorbance in pH 6.820.0850.08240.1410.14850.1890.186100.3330.3410.251150.5100.497200.7010.6510.467250.8520.806300.746400.989 FIG 7.4 standard curve at PH 1.2 BufferFig 7.5 standard curve at PH 4.5 Buffer Fig 7.6 standard curve at PH 6.8 Buffer reckoning of initial dit and maintenance loony toons for the design of elementary osmotic pump of famotidine for 12 hoursThere are no sustained fire formu lations for famotidine in the market, hence the total dose (DT) consisting of initial (DI) and maintenance doses (DM) for formulating the famotidine sustained release was deliberate as per Robinson and Eriksen equation with a vigour order release principle36 . In this profile the rate of delivery is independent of the amount of drug remaining in the dosage form and constant over cartridge holder as shown by the Eq. 6.1 Drug availability rate k0 = Rate in = Rate out Eq. 6.1Where, k0 is the zero order rate constant for drug release (amount per time).DI is required to give initial rapid release of drug so as to attain the marginal therapeutic level immediately after dosing. Inital dose (DI) = CSSAVG Vd Eq. 6.2 F Where, C ssavg is the average steady state plasma level, V d is the volume of distribution and F is the fraction of dose absorbed. k0 = DIKel Eq. 6.3Where, Kel is overall first order drug elimination rate constant (per hour). thence k 0 should be equal to the elimination rate constant so as to maintain the steady state condition.In general the total dose required (D T) is the sum total of maintenance dose (DM) and the initial dose (DI) DT = D I + D M Eq. 6.4In practice, D M (mg) is released over a period of time and is equal to the product of H (the number of hours for which sustained action is desired after initial dose) and the zero order rate constant, k0 (mg/hr).Therefore the Eq. 6.4 can be expressed as DT = D I + k0H Eq. 6.5Ideally the maintenance dose (DM) is released after DI has produced a minimum therapeutic blood level of the drug. However due to the limits of formulations, drug release even starts from DM also from the beginning i.e. at t=0, thus increasing the initial drug level in the blood. Hence it is necessary to reduce the initial dose of the drug to account for the excess release for drug from DM by using a field of study factor, k0tp. This correction factor is the amount of drug provided by DM during the period from t=0 to the t ime of the peak drug level, tp. The corrected initial dose (DI*) becomes DI-(k0tp). Then the total dose is DT = DI* + k0H = (D I k0tp) + k0H Eq. 6.6Pharmacokinetic parameters of famotidineElimination half life (t1/2) of famotidine is 3 hrs (average of 2.5 to 3.5 hrs), the time to reach peak plasma (t p) is 3 hrs and Vd = 80.5 L and F = 0.4 54,55 . From the literature of the PEPCID (innovator product of famotidine in USA) label and pharmacological review information 49,, it was found that the plasma levels after seven-fold doses are similar to those after single doses indicating the C max is similar to Cssavg , therefore Cmax of 0.07 mg/L was taken as C ssavg .Calculation of D I and DMThe initial dose (DI), corrected initial dose (DI*), maintenance dose (DM) and total dose (DT) were calculated according to calculations described above.Calculation of elimination rate constant Elimination rate constant (K el ) = 0.693/t 1/2= 0.693/3 = 0.231 hr -1Calculation of initial dose Inital do se (DI) = CSSAVG Vd Eq. 6.2 F = (0.07 X 80.5)/0.4= 14.0875 mgCalculation of desired input rate (k 0)Desired input rate from maintenance dose (k 0) = DIKel= 14.0875 X 0.231 = 3.25 mg/hrCalculation of maintenance dose Maintenance dose (DM) = k0H (Since, H = the number of hours for which sustained action is desired after initial dose = (12-1) = 11 hrs)= 3.25 X 11 = 35.796 mgCalculation of corrected initial dose DI*DI* = DI (k0tp)= 14.087 (3.25 X 3 ) = 4.93 mgCalculation of total doseTotal dose (D T) = D I* + D M= 4.93 + 35.796 = 40.726 mgFrom the above calculations the total dose obtained for sustained release of famotidine for 12 hrs is 40.726 mg. The total dose was rounded off to 40mg for the convenience. Initially the dosage form should release the total initial dose (i.e. 4.93 mg 5.0 of drug, means 11% of total 50 mg dose) in the first 1 hr followed by maintenance dose (i.e. 40-5=35 mg of drug) for up to 12 hrs there after at a release rate of 3.25 mg/hr (i.e. 8.125% of total 40 mg dose). Based on these assumptions the theoretical release profile was predicted and shown Table 6.7 Predicted theoretical release profileTime (hrs)% CDD111.4219.425327.45435.475543.5651.525759.55867.5751083.6251299.675JNTUA-OTRI, Ananthapuramu 1